This patch series introduces UFFDIO_MOVE feature to userfaultfd, which has long been implemented and maintained by Andrea in his local tree [1], but was not upstreamed due to lack of use cases where this approach would be better than allocating a new page and copying the contents. Previous upstraming attempts could be found at [6] and [7].
UFFDIO_COPY performs ~20% better than UFFDIO_MOVE when the application needs pages to be allocated [2]. However, with UFFDIO_MOVE, if pages are available (in userspace) for recycling, as is usually the case in heap compaction algorithms, then we can avoid the page allocation and memcpy (done by UFFDIO_COPY). Also, since the pages are recycled in the userspace, we avoid the need to release (via madvise) the pages back to the kernel [3]. We see over 40% reduction (on a Google pixel 6 device) in the compacting thread’s completion time by using UFFDIO_MOVE vs. UFFDIO_COPY. This was measured using a benchmark that emulates a heap compaction implementation using userfaultfd (to allow concurrent accesses by application threads). More details of the usecase are explained in [3].
Furthermore, UFFDIO_MOVE enables moving swapped-out pages without touching them within the same vma. Today, it can only be done by mremap, however it forces splitting the vma.
TODOs for follow-up improvements: - cross-mm support. Known differences from single-mm and missing pieces: - memcg recharging (might need to isolate pages in the process) - mm counters - cross-mm deposit table moves - cross-mm test - document the address space where src and dest reside in struct uffdio_move
- TLB flush batching. Will require extensive changes to PTL locking in move_pages_pte(). OTOH that might let us reuse parts of mremap code.
Changes since v5 [10]: - added logic to split large folios in move_pages_pte(), per David Hildenbrand - added check for PAE before split_huge_pmd() to avoid the split if the move operation can't be done - replaced calls to default_huge_page_size() with read_pmd_pagesize() in uffd_move_pmd test, per David Hildenbrand - fixed the condition in uffd_move_test_common() checking if area alignment is needed
Changes since v4 [9]: - added Acked-by in patch 1, per Peter Xu - added description for ctx, mm and mode parameters of move_pages(), per kernel test robot - added Reviewed-by's, per Peter Xu and Axel Rasmussen - removed unused operations in uffd_test_case_ops - refactored uffd-unit-test changes to avoid using global variables and handle pmd moves without page size overrides, per Peter Xu
Changes since v3 [8]: - changed retry path in folio_lock_anon_vma_read() to unlock and then relock RCU, per Peter Xu - removed cross-mm support from initial patchset, per David Hildenbrand - replaced BUG_ONs with VM_WARN_ON or WARN_ON_ONCE, per David Hildenbrand - added missing cache flushing, per Lokesh Gidra and Peter Xu - updated manpage text in the patch description, per Peter Xu - renamed internal functions from "remap" to "move", per Peter Xu - added mmap_changing check after taking mmap_lock, per Peter Xu - changed uffd context check to ensure dst_mm is registered onto uffd we are operating on, Peter Xu and David Hildenbrand - changed to non-maybe variants of maybe*_mkwrite(), per David Hildenbrand - fixed warning for CONFIG_TRANSPARENT_HUGEPAGE=n, per kernel test robot - comments cleanup, per David Hildenbrand and Peter Xu - checks for VM_IO,VM_PFNMAP,VM_HUGETLB,..., per David Hildenbrand - prevent moving pinned pages, per Peter Xu - changed uffd tests to call move uffd_test_ctx_clear() at the end of the test run instead of in the beginning of the next run - added support for testcase-specific ops - added test for moving PMD-aligned blocks
Changes since v2 [5]: - renamed UFFDIO_REMAP to UFFDIO_MOVE, per David Hildenbrand - rebase over mm-unstable to use folio_move_anon_rmap(), per David Hildenbrand - added text for manpage explaining DONTFORK and KSM requirements for this feature, per David Hildenbrand - check for anon_vma changes in the fast path of folio_lock_anon_vma_read, per Peter Xu - updated the title and description of the first patch, per David Hildenbrand - updating comments in folio_lock_anon_vma_read() explaining the need for anon_vma checks, per David Hildenbrand - changed all mapcount checks to PageAnonExclusive, per Jann Horn and David Hildenbrand - changed counters in remap_swap_pte() from MM_ANONPAGES to MM_SWAPENTS, per Jann Horn - added a check for PTE change after folio is locked in remap_pages_pte(), per Jann Horn - added handling of PMD migration entries and bailout when pmd_devmap(), per Jann Horn - added checks to ensure both src and dst VMAs are writable, per Peter Xu - added UFFD_FEATURE_MOVE, per Peter Xu - removed obsolete comments, per Peter Xu - renamed remap_anon_pte to remap_present_pte, per Peter Xu - added a comment for folio_get_anon_vma() explaining the need for anon_vma checks, per Peter Xu - changed error handling in remap_pages() to make it more clear, per Peter Xu - changed EFAULT to EAGAIN to retry when a hugepage appears or disappears from under us, per Peter Xu - added links to previous upstreaming attempts, per David Hildenbrand
Changes since v1 [4]: - add mmget_not_zero in userfaultfd_remap, per Jann Horn - removed extern from function definitions, per Matthew Wilcox - converted to folios in remap_pages_huge_pmd, per Matthew Wilcox - use PageAnonExclusive in remap_pages_huge_pmd, per David Hildenbrand - handle pgtable transfers between MMs, per Jann Horn - ignore concurrent A/D pte bit changes, per Jann Horn - split functions into smaller units, per David Hildenbrand - test for folio_test_large in remap_anon_pte, per Matthew Wilcox - use pte_swp_exclusive for swapcount check, per David Hildenbrand - eliminated use of mmu_notifier_invalidate_range_start_nonblock, per Jann Horn - simplified THP alignment checks, per Jann Horn - refactored the loop inside remap_pages, per Jann Horn - additional clarifying comments, per Jann Horn
Main changes since Andrea's last version [1]: - Trivial translations from page to folio, mmap_sem to mmap_lock - Replace pmd_trans_unstable() with pte_offset_map_nolock() and handle its possible failure - Move pte mapping into remap_pages_pte to allow for retries when source page or anon_vma is contended. Since pte_offset_map_nolock() start RCU read section, we can't block anymore after mapping a pte, so have to unmap the ptesm do the locking and retry. - Add and use anon_vma_trylock_write() to avoid blocking while in RCU read section. - Accommodate changes in mmu_notifier_range_init() API, switch to mmu_notifier_invalidate_range_start_nonblock() to avoid blocking while in RCU read section. - Open-code now removed __swp_swapcount() - Replace pmd_read_atomic() with pmdp_get_lockless() - Add new selftest for UFFDIO_MOVE
[1] https://gitlab.com/aarcange/aa/-/commit/2aec7aea56b10438a3881a20a411aa4b1fc1... [2] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redhat... [3] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyjn... [4] https://lore.kernel.org/all/20230914152620.2743033-1-surenb@google.com/ [5] https://lore.kernel.org/all/20230923013148.1390521-1-surenb@google.com/ [6] https://lore.kernel.org/all/1425575884-2574-21-git-send-email-aarcange@redha... [7] https://lore.kernel.org/all/cover.1547251023.git.blake.caldwell@colorado.edu... [8] https://lore.kernel.org/all/20231009064230.2952396-1-surenb@google.com/ [9] https://lore.kernel.org/all/20231028003819.652322-1-surenb@google.com/ [10] https://lore.kernel.org/all/20231121171643.3719880-1-surenb@google.com/
Andrea Arcangeli (2): mm/rmap: support move to different root anon_vma in folio_move_anon_rmap() userfaultfd: UFFDIO_MOVE uABI
Suren Baghdasaryan (3): selftests/mm: call uffd_test_ctx_clear at the end of the test selftests/mm: add uffd_test_case_ops to allow test case-specific operations selftests/mm: add UFFDIO_MOVE ioctl test
Documentation/admin-guide/mm/userfaultfd.rst | 3 + fs/userfaultfd.c | 72 +++ include/linux/rmap.h | 5 + include/linux/userfaultfd_k.h | 11 + include/uapi/linux/userfaultfd.h | 29 +- mm/huge_memory.c | 122 ++++ mm/khugepaged.c | 3 + mm/rmap.c | 30 + mm/userfaultfd.c | 614 +++++++++++++++++++ tools/testing/selftests/mm/uffd-common.c | 39 +- tools/testing/selftests/mm/uffd-common.h | 9 + tools/testing/selftests/mm/uffd-stress.c | 5 +- tools/testing/selftests/mm/uffd-unit-tests.c | 192 ++++++ 13 files changed, 1130 insertions(+), 4 deletions(-)
From: Andrea Arcangeli aarcange@redhat.com
For now, folio_move_anon_rmap() was only used to move a folio to a different anon_vma after fork(), whereby the root anon_vma stayed unchanged. For that, it was sufficient to hold the folio lock when calling folio_move_anon_rmap().
However, we want to make use of folio_move_anon_rmap() to move folios between VMAs that have a different root anon_vma. As folio_referenced() performs an RMAP walk without holding the folio lock but only holding the anon_vma in read mode, holding the folio lock is insufficient.
When moving to an anon_vma with a different root anon_vma, we'll have to hold both, the folio lock and the anon_vma lock in write mode. Consequently, whenever we succeeded in folio_lock_anon_vma_read() to read-lock the anon_vma, we have to re-check if the mapping was changed in the meantime. If that was the case, we have to retry.
Note that folio_move_anon_rmap() must only be called if the anon page is exclusive to a process, and must not be called on KSM folios.
This is a preparation for UFFDIO_MOVE, which will hold the folio lock, the anon_vma lock in write mode, and the mmap_lock in read mode.
Signed-off-by: Andrea Arcangeli aarcange@redhat.com Signed-off-by: Suren Baghdasaryan surenb@google.com Acked-by: Peter Xu peterx@redhat.com --- mm/rmap.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
diff --git a/mm/rmap.c b/mm/rmap.c index 7a27a2b41802..525c5bc0b0b3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -542,6 +542,7 @@ struct anon_vma *folio_lock_anon_vma_read(struct folio *folio, struct anon_vma *root_anon_vma; unsigned long anon_mapping;
+retry: rcu_read_lock(); anon_mapping = (unsigned long)READ_ONCE(folio->mapping); if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) @@ -552,6 +553,17 @@ struct anon_vma *folio_lock_anon_vma_read(struct folio *folio, anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); root_anon_vma = READ_ONCE(anon_vma->root); if (down_read_trylock(&root_anon_vma->rwsem)) { + /* + * folio_move_anon_rmap() might have changed the anon_vma as we + * might not hold the folio lock here. + */ + if (unlikely((unsigned long)READ_ONCE(folio->mapping) != + anon_mapping)) { + up_read(&root_anon_vma->rwsem); + rcu_read_unlock(); + goto retry; + } + /* * If the folio is still mapped, then this anon_vma is still * its anon_vma, and holding the mutex ensures that it will @@ -586,6 +598,18 @@ struct anon_vma *folio_lock_anon_vma_read(struct folio *folio, rcu_read_unlock(); anon_vma_lock_read(anon_vma);
+ /* + * folio_move_anon_rmap() might have changed the anon_vma as we might + * not hold the folio lock here. + */ + if (unlikely((unsigned long)READ_ONCE(folio->mapping) != + anon_mapping)) { + anon_vma_unlock_read(anon_vma); + put_anon_vma(anon_vma); + anon_vma = NULL; + goto retry; + } + if (atomic_dec_and_test(&anon_vma->refcount)) { /* * Oops, we held the last refcount, release the lock
From: Andrea Arcangeli aarcange@redhat.com
Implement the uABI of UFFDIO_MOVE ioctl. UFFDIO_COPY performs ~20% better than UFFDIO_MOVE when the application needs pages to be allocated [1]. However, with UFFDIO_MOVE, if pages are available (in userspace) for recycling, as is usually the case in heap compaction algorithms, then we can avoid the page allocation and memcpy (done by UFFDIO_COPY). Also, since the pages are recycled in the userspace, we avoid the need to release (via madvise) the pages back to the kernel [2]. We see over 40% reduction (on a Google pixel 6 device) in the compacting thread’s completion time by using UFFDIO_MOVE vs. UFFDIO_COPY. This was measured using a benchmark that emulates a heap compaction implementation using userfaultfd (to allow concurrent accesses by application threads). More details of the usecase are explained in [2]. Furthermore, UFFDIO_MOVE enables moving swapped-out pages without touching them within the same vma. Today, it can only be done by mremap, however it forces splitting the vma.
[1] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redhat... [2] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyjn...
Update for the ioctl_userfaultfd(2) manpage:
UFFDIO_MOVE (Since Linux xxx) Move a continuous memory chunk into the userfault registered range and optionally wake up the blocked thread. The source and destination addresses and the number of bytes to move are specified by the src, dst, and len fields of the uffdio_move structure pointed to by argp:
struct uffdio_move { __u64 dst; /* Destination of move */ __u64 src; /* Source of move */ __u64 len; /* Number of bytes to move */ __u64 mode; /* Flags controlling behavior of move */ __s64 move; /* Number of bytes moved, or negated error */ };
The following value may be bitwise ORed in mode to change the behavior of the UFFDIO_MOVE operation:
UFFDIO_MOVE_MODE_DONTWAKE Do not wake up the thread that waits for page-fault resolution
UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES Allow holes in the source virtual range that is being moved. When not specified, the holes will result in ENOENT error. When specified, the holes will be accounted as successfully moved memory. This is mostly useful to move hugepage aligned virtual regions without knowing if there are transparent hugepages in the regions or not, but preventing the risk of having to split the hugepage during the operation.
The move field is used by the kernel to return the number of bytes that was actually moved, or an error (a negated errno- style value). If the value returned in move doesn't match the value that was specified in len, the operation fails with the error EAGAIN. The move field is output-only; it is not read by the UFFDIO_MOVE operation.
The operation may fail for various reasons. Usually, remapping of pages that are not exclusive to the given process fail; once KSM might deduplicate pages or fork() COW-shares pages during fork() with child processes, they are no longer exclusive. Further, the kernel might only perform lightweight checks for detecting whether the pages are exclusive, and return -EBUSY in case that check fails. To make the operation more likely to succeed, KSM should be disabled, fork() should be avoided or MADV_DONTFORK should be configured for the source VMA before fork().
This ioctl(2) operation returns 0 on success. In this case, the entire area was moved. On error, -1 is returned and errno is set to indicate the error. Possible errors include:
EAGAIN The number of bytes moved (i.e., the value returned in the move field) does not equal the value that was specified in the len field.
EINVAL Either dst or len was not a multiple of the system page size, or the range specified by src and len or dst and len was invalid.
EINVAL An invalid bit was specified in the mode field.
ENOENT The source virtual memory range has unmapped holes and UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES is not set.
EEXIST The destination virtual memory range is fully or partially mapped.
EBUSY The pages in the source virtual memory range are either pinned or not exclusive to the process. The kernel might only perform lightweight checks for detecting whether the pages are exclusive. To make the operation more likely to succeed, KSM should be disabled, fork() should be avoided or MADV_DONTFORK should be configured for the source virtual memory area before fork().
ENOMEM Allocating memory needed for the operation failed.
ESRCH The target process has exited at the time of a UFFDIO_MOVE operation.
Signed-off-by: Andrea Arcangeli aarcange@redhat.com Signed-off-by: Suren Baghdasaryan surenb@google.com --- Documentation/admin-guide/mm/userfaultfd.rst | 3 + fs/userfaultfd.c | 72 +++ include/linux/rmap.h | 5 + include/linux/userfaultfd_k.h | 11 + include/uapi/linux/userfaultfd.h | 29 +- mm/huge_memory.c | 122 ++++ mm/khugepaged.c | 3 + mm/rmap.c | 6 + mm/userfaultfd.c | 614 +++++++++++++++++++ 9 files changed, 864 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 203e26da5f92..e5cc8848dcb3 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -113,6 +113,9 @@ events, except page fault notifications, may be generated: areas. ``UFFD_FEATURE_MINOR_SHMEM`` is the analogous feature indicating support for shmem virtual memory areas.
+- ``UFFD_FEATURE_MOVE`` indicates that the kernel supports moving an + existing page contents from userspace. + The userland application should set the feature flags it intends to use when invoking the ``UFFDIO_API`` ioctl, to request that those features be enabled if supported. diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index e8af40b05549..6e2a4d6a0d8f 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -2005,6 +2005,75 @@ static inline unsigned int uffd_ctx_features(__u64 user_features) return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED; }
+static int userfaultfd_move(struct userfaultfd_ctx *ctx, + unsigned long arg) +{ + __s64 ret; + struct uffdio_move uffdio_move; + struct uffdio_move __user *user_uffdio_move; + struct userfaultfd_wake_range range; + struct mm_struct *mm = ctx->mm; + + user_uffdio_move = (struct uffdio_move __user *) arg; + + if (atomic_read(&ctx->mmap_changing)) + return -EAGAIN; + + if (copy_from_user(&uffdio_move, user_uffdio_move, + /* don't copy "move" last field */ + sizeof(uffdio_move)-sizeof(__s64))) + return -EFAULT; + + /* Do not allow cross-mm moves. */ + if (mm != current->mm) + return -EINVAL; + + ret = validate_range(mm, uffdio_move.dst, uffdio_move.len); + if (ret) + return ret; + + ret = validate_range(mm, uffdio_move.src, uffdio_move.len); + if (ret) + return ret; + + if (uffdio_move.mode & ~(UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES| + UFFDIO_MOVE_MODE_DONTWAKE)) + return -EINVAL; + + if (mmget_not_zero(mm)) { + mmap_read_lock(mm); + + /* Re-check after taking mmap_lock */ + if (likely(!atomic_read(&ctx->mmap_changing))) + ret = move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src, + uffdio_move.len, uffdio_move.mode); + else + ret = -EINVAL; + + mmap_read_unlock(mm); + mmput(mm); + } else { + return -ESRCH; + } + + if (unlikely(put_user(ret, &user_uffdio_move->move))) + return -EFAULT; + if (ret < 0) + goto out; + + /* len == 0 would wake all */ + VM_WARN_ON(!ret); + range.len = ret; + if (!(uffdio_move.mode & UFFDIO_MOVE_MODE_DONTWAKE)) { + range.start = uffdio_move.dst; + wake_userfault(ctx, &range); + } + ret = range.len == uffdio_move.len ? 0 : -EAGAIN; + +out: + return ret; +} + /* * userland asks for a certain API version and we return which bits * and ioctl commands are implemented in this kernel for such API @@ -2097,6 +2166,9 @@ static long userfaultfd_ioctl(struct file *file, unsigned cmd, case UFFDIO_ZEROPAGE: ret = userfaultfd_zeropage(ctx, arg); break; + case UFFDIO_MOVE: + ret = userfaultfd_move(ctx, arg); + break; case UFFDIO_WRITEPROTECT: ret = userfaultfd_writeprotect(ctx, arg); break; diff --git a/include/linux/rmap.h b/include/linux/rmap.h index b26fe858fd44..8034eda972e5 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -121,6 +121,11 @@ static inline void anon_vma_lock_write(struct anon_vma *anon_vma) down_write(&anon_vma->root->rwsem); }
+static inline int anon_vma_trylock_write(struct anon_vma *anon_vma) +{ + return down_write_trylock(&anon_vma->root->rwsem); +} + static inline void anon_vma_unlock_write(struct anon_vma *anon_vma) { up_write(&anon_vma->root->rwsem); diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index f2dc19f40d05..e4056547fbe6 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -93,6 +93,17 @@ extern int mwriteprotect_range(struct mm_struct *dst_mm, extern long uffd_wp_range(struct vm_area_struct *vma, unsigned long start, unsigned long len, bool enable_wp);
+/* move_pages */ +void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2); +void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2); +ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, + unsigned long dst_start, unsigned long src_start, + unsigned long len, __u64 flags); +int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval, + struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma, + unsigned long dst_addr, unsigned long src_addr); + /* mm helpers */ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, struct vm_userfaultfd_ctx vm_ctx) diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 0dbc81015018..2841e4ea8f2c 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -41,7 +41,8 @@ UFFD_FEATURE_WP_HUGETLBFS_SHMEM | \ UFFD_FEATURE_WP_UNPOPULATED | \ UFFD_FEATURE_POISON | \ - UFFD_FEATURE_WP_ASYNC) + UFFD_FEATURE_WP_ASYNC | \ + UFFD_FEATURE_MOVE) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -50,6 +51,7 @@ ((__u64)1 << _UFFDIO_WAKE | \ (__u64)1 << _UFFDIO_COPY | \ (__u64)1 << _UFFDIO_ZEROPAGE | \ + (__u64)1 << _UFFDIO_MOVE | \ (__u64)1 << _UFFDIO_WRITEPROTECT | \ (__u64)1 << _UFFDIO_CONTINUE | \ (__u64)1 << _UFFDIO_POISON) @@ -73,6 +75,7 @@ #define _UFFDIO_WAKE (0x02) #define _UFFDIO_COPY (0x03) #define _UFFDIO_ZEROPAGE (0x04) +#define _UFFDIO_MOVE (0x05) #define _UFFDIO_WRITEPROTECT (0x06) #define _UFFDIO_CONTINUE (0x07) #define _UFFDIO_POISON (0x08) @@ -92,6 +95,8 @@ struct uffdio_copy) #define UFFDIO_ZEROPAGE _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \ struct uffdio_zeropage) +#define UFFDIO_MOVE _IOWR(UFFDIO, _UFFDIO_MOVE, \ + struct uffdio_move) #define UFFDIO_WRITEPROTECT _IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \ struct uffdio_writeprotect) #define UFFDIO_CONTINUE _IOWR(UFFDIO, _UFFDIO_CONTINUE, \ @@ -222,6 +227,9 @@ struct uffdio_api { * asynchronous mode is supported in which the write fault is * automatically resolved and write-protection is un-set. * It implies UFFD_FEATURE_WP_UNPOPULATED. + * + * UFFD_FEATURE_MOVE indicates that the kernel supports moving an + * existing page contents from userspace. */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) @@ -239,6 +247,7 @@ struct uffdio_api { #define UFFD_FEATURE_WP_UNPOPULATED (1<<13) #define UFFD_FEATURE_POISON (1<<14) #define UFFD_FEATURE_WP_ASYNC (1<<15) +#define UFFD_FEATURE_MOVE (1<<16) __u64 features;
__u64 ioctls; @@ -347,6 +356,24 @@ struct uffdio_poison { __s64 updated; };
+struct uffdio_move { + __u64 dst; + __u64 src; + __u64 len; + /* + * Especially if used to atomically remove memory from the + * address space the wake on the dst range is not needed. + */ +#define UFFDIO_MOVE_MODE_DONTWAKE ((__u64)1<<0) +#define UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES ((__u64)1<<1) + __u64 mode; + /* + * "move" is written by the ioctl and must be at the end: the + * copy_from_user will not read the last 8 bytes. + */ + __s64 move; +}; + /* * Flags for the userfaultfd(2) system call itself. */ diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 4f542444a91f..315968db1ca4 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1964,6 +1964,128 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, return ret; }
+#ifdef CONFIG_USERFAULTFD +/* + * The PT lock for src_pmd and the mmap_lock for reading are held by + * the caller, but it must return after releasing the page_table_lock. + * Just move the page from src_pmd to dst_pmd if possible. + * Return zero if succeeded in moving the page, -EAGAIN if it needs to be + * repeated by the caller, or other errors in case of failure. + */ +int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval, + struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + unsigned long dst_addr, unsigned long src_addr) +{ + pmd_t _dst_pmd, src_pmdval; + struct page *src_page; + struct folio *src_folio; + struct anon_vma *src_anon_vma; + spinlock_t *src_ptl, *dst_ptl; + pgtable_t src_pgtable; + struct mmu_notifier_range range; + int err = 0; + + src_pmdval = *src_pmd; + src_ptl = pmd_lockptr(mm, src_pmd); + + lockdep_assert_held(src_ptl); + mmap_assert_locked(mm); + + /* Sanity checks before the operation */ + if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE_PMD_MASK) || + WARN_ON_ONCE(dst_addr & ~HPAGE_PMD_MASK)) { + spin_unlock(src_ptl); + return -EINVAL; + } + + if (!pmd_trans_huge(src_pmdval)) { + spin_unlock(src_ptl); + if (is_pmd_migration_entry(src_pmdval)) { + pmd_migration_entry_wait(mm, &src_pmdval); + return -EAGAIN; + } + return -ENOENT; + } + + src_page = pmd_page(src_pmdval); + if (unlikely(!PageAnonExclusive(src_page))) { + spin_unlock(src_ptl); + return -EBUSY; + } + + src_folio = page_folio(src_page); + folio_get(src_folio); + spin_unlock(src_ptl); + + flush_cache_range(src_vma, src_addr, src_addr + HPAGE_PMD_SIZE); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, src_addr, + src_addr + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); + + folio_lock(src_folio); + + /* + * split_huge_page walks the anon_vma chain without the page + * lock. Serialize against it with the anon_vma lock, the page + * lock is not enough. + */ + src_anon_vma = folio_get_anon_vma(src_folio); + if (!src_anon_vma) { + err = -EAGAIN; + goto unlock_folio; + } + anon_vma_lock_write(src_anon_vma); + + dst_ptl = pmd_lockptr(mm, dst_pmd); + double_pt_lock(src_ptl, dst_ptl); + if (unlikely(!pmd_same(*src_pmd, src_pmdval) || + !pmd_same(*dst_pmd, dst_pmdval))) { + err = -EAGAIN; + goto unlock_ptls; + } + if (folio_maybe_dma_pinned(src_folio) || + !PageAnonExclusive(&src_folio->page)) { + err = -EBUSY; + goto unlock_ptls; + } + + if (WARN_ON_ONCE(!folio_test_head(src_folio)) || + WARN_ON_ONCE(!folio_test_anon(src_folio))) { + err = -EBUSY; + goto unlock_ptls; + } + + folio_move_anon_rmap(src_folio, dst_vma); + WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr)); + + src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); + /* Folio got pinned from under us. Put it back and fail the move. */ + if (folio_maybe_dma_pinned(src_folio)) { + set_pmd_at(mm, src_addr, src_pmd, src_pmdval); + err = -EBUSY; + goto unlock_ptls; + } + + _dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot); + /* Follow mremap() behavior and treat the entry dirty after the move */ + _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma); + set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd); + + src_pgtable = pgtable_trans_huge_withdraw(mm, src_pmd); + pgtable_trans_huge_deposit(mm, dst_pmd, src_pgtable); +unlock_ptls: + double_pt_unlock(src_ptl, dst_ptl); + anon_vma_unlock_write(src_anon_vma); + put_anon_vma(src_anon_vma); +unlock_folio: + /* unblock rmap walks */ + folio_unlock(src_folio); + mmu_notifier_invalidate_range_end(&range); + folio_put(src_folio); + return err; +} +#endif /* CONFIG_USERFAULTFD */ + /* * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. * diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 064654717843..0da6937572cf 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1139,6 +1139,9 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, * Prevent all access to pagetables with the exception of * gup_fast later handled by the ptep_clear_flush and the VM * handled by the anon_vma lock + PG_lock. + * + * UFFDIO_MOVE is prevented to race as well thanks to the + * mmap_lock. */ mmap_write_lock(mm); result = hugepage_vma_revalidate(mm, address, true, &vma, cc); diff --git a/mm/rmap.c b/mm/rmap.c index 525c5bc0b0b3..de9426ad0f1b 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -490,6 +490,12 @@ void __init anon_vma_init(void) * page_remove_rmap() that the anon_vma pointer from page->mapping is valid * if there is a mapcount, we can dereference the anon_vma after observing * those. + * + * NOTE: the caller should normally hold folio lock when calling this. If + * not, the caller needs to double check the anon_vma didn't change after + * taking the anon_vma lock for either read or write (UFFDIO_MOVE can modify it + * concurrently without folio lock protection). See folio_lock_anon_vma_read() + * which has already covered that, and comment above remap_pages(). */ struct anon_vma *folio_get_anon_vma(struct folio *folio) { diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 0b6ca553bebe..9ec814e47e99 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -842,3 +842,617 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, mmap_read_unlock(dst_mm); return err; } + + +void double_pt_lock(spinlock_t *ptl1, + spinlock_t *ptl2) + __acquires(ptl1) + __acquires(ptl2) +{ + spinlock_t *ptl_tmp; + + if (ptl1 > ptl2) { + /* exchange ptl1 and ptl2 */ + ptl_tmp = ptl1; + ptl1 = ptl2; + ptl2 = ptl_tmp; + } + /* lock in virtual address order to avoid lock inversion */ + spin_lock(ptl1); + if (ptl1 != ptl2) + spin_lock_nested(ptl2, SINGLE_DEPTH_NESTING); + else + __acquire(ptl2); +} + +void double_pt_unlock(spinlock_t *ptl1, + spinlock_t *ptl2) + __releases(ptl1) + __releases(ptl2) +{ + spin_unlock(ptl1); + if (ptl1 != ptl2) + spin_unlock(ptl2); + else + __release(ptl2); +} + + +static int move_present_pte(struct mm_struct *mm, + struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma, + unsigned long dst_addr, unsigned long src_addr, + pte_t *dst_pte, pte_t *src_pte, + pte_t orig_dst_pte, pte_t orig_src_pte, + spinlock_t *dst_ptl, spinlock_t *src_ptl, + struct folio *src_folio) +{ + int err = 0; + + double_pt_lock(dst_ptl, src_ptl); + + if (!pte_same(*src_pte, orig_src_pte) || + !pte_same(*dst_pte, orig_dst_pte)) { + err = -EAGAIN; + goto out; + } + if (folio_test_large(src_folio) || + folio_maybe_dma_pinned(src_folio) || + !PageAnonExclusive(&src_folio->page)) { + err = -EBUSY; + goto out; + } + + folio_move_anon_rmap(src_folio, dst_vma); + WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr)); + + orig_src_pte = ptep_clear_flush(src_vma, src_addr, src_pte); + /* Folio got pinned from under us. Put it back and fail the move. */ + if (folio_maybe_dma_pinned(src_folio)) { + set_pte_at(mm, src_addr, src_pte, orig_src_pte); + err = -EBUSY; + goto out; + } + + orig_dst_pte = mk_pte(&src_folio->page, dst_vma->vm_page_prot); + /* Follow mremap() behavior and treat the entry dirty after the move */ + orig_dst_pte = pte_mkwrite(pte_mkdirty(orig_dst_pte), dst_vma); + + set_pte_at(mm, dst_addr, dst_pte, orig_dst_pte); +out: + double_pt_unlock(dst_ptl, src_ptl); + return err; +} + +static int move_swap_pte(struct mm_struct *mm, + unsigned long dst_addr, unsigned long src_addr, + pte_t *dst_pte, pte_t *src_pte, + pte_t orig_dst_pte, pte_t orig_src_pte, + spinlock_t *dst_ptl, spinlock_t *src_ptl) +{ + if (!pte_swp_exclusive(orig_src_pte)) + return -EBUSY; + + double_pt_lock(dst_ptl, src_ptl); + + if (!pte_same(*src_pte, orig_src_pte) || + !pte_same(*dst_pte, orig_dst_pte)) { + double_pt_unlock(dst_ptl, src_ptl); + return -EAGAIN; + } + + orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte); + set_pte_at(mm, dst_addr, dst_pte, orig_src_pte); + double_pt_unlock(dst_ptl, src_ptl); + + return 0; +} + +/* + * The mmap_lock for reading is held by the caller. Just move the page + * from src_pmd to dst_pmd if possible, and return true if succeeded + * in moving the page. + */ +static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, + struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma, + unsigned long dst_addr, unsigned long src_addr, + __u64 mode) +{ + swp_entry_t entry; + pte_t orig_src_pte, orig_dst_pte; + pte_t src_folio_pte; + spinlock_t *src_ptl, *dst_ptl; + pte_t *src_pte = NULL; + pte_t *dst_pte = NULL; + + struct folio *src_folio = NULL; + struct anon_vma *src_anon_vma = NULL; + struct mmu_notifier_range range; + int err = 0; + + flush_cache_range(src_vma, src_addr, src_addr + PAGE_SIZE); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, + src_addr, src_addr + PAGE_SIZE); + mmu_notifier_invalidate_range_start(&range); +retry: + dst_pte = pte_offset_map_nolock(mm, dst_pmd, dst_addr, &dst_ptl); + + /* Retry if a huge pmd materialized from under us */ + if (unlikely(!dst_pte)) { + err = -EAGAIN; + goto out; + } + + src_pte = pte_offset_map_nolock(mm, src_pmd, src_addr, &src_ptl); + + /* + * We held the mmap_lock for reading so MADV_DONTNEED + * can zap transparent huge pages under us, or the + * transparent huge page fault can establish new + * transparent huge pages under us. + */ + if (unlikely(!src_pte)) { + err = -EAGAIN; + goto out; + } + + /* Sanity checks before the operation */ + if (WARN_ON_ONCE(pmd_none(*dst_pmd)) || WARN_ON_ONCE(pmd_none(*src_pmd)) || + WARN_ON_ONCE(pmd_trans_huge(*dst_pmd)) || WARN_ON_ONCE(pmd_trans_huge(*src_pmd))) { + err = -EINVAL; + goto out; + } + + spin_lock(dst_ptl); + orig_dst_pte = *dst_pte; + spin_unlock(dst_ptl); + if (!pte_none(orig_dst_pte)) { + err = -EEXIST; + goto out; + } + + spin_lock(src_ptl); + orig_src_pte = *src_pte; + spin_unlock(src_ptl); + if (pte_none(orig_src_pte)) { + if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) + err = -ENOENT; + else /* nothing to do to move a hole */ + err = 0; + goto out; + } + + /* If PTE changed after we locked the folio them start over */ + if (src_folio && unlikely(!pte_same(src_folio_pte, orig_src_pte))) { + err = -EAGAIN; + goto out; + } + + if (pte_present(orig_src_pte)) { + /* + * Pin and lock both source folio and anon_vma. Since we are in + * RCU read section, we can't block, so on contention have to + * unmap the ptes, obtain the lock and retry. + */ + if (!src_folio) { + struct folio *folio; + + /* + * Pin the page while holding the lock to be sure the + * page isn't freed under us + */ + spin_lock(src_ptl); + if (!pte_same(orig_src_pte, *src_pte)) { + spin_unlock(src_ptl); + err = -EAGAIN; + goto out; + } + + folio = vm_normal_folio(src_vma, src_addr, orig_src_pte); + if (!folio || !PageAnonExclusive(&folio->page)) { + spin_unlock(src_ptl); + err = -EBUSY; + goto out; + } + + folio_get(folio); + src_folio = folio; + src_folio_pte = orig_src_pte; + spin_unlock(src_ptl); + + if (!folio_trylock(src_folio)) { + pte_unmap(&orig_src_pte); + pte_unmap(&orig_dst_pte); + src_pte = dst_pte = NULL; + /* now we can block and wait */ + folio_lock(src_folio); + goto retry; + } + + if (WARN_ON_ONCE(!folio_test_anon(src_folio))) { + err = -EBUSY; + goto out; + } + } + + /* at this point we have src_folio locked */ + if (folio_test_large(src_folio)) { + err = split_folio(src_folio); + if (err) + goto out; + } + + if (!src_anon_vma) { + /* + * folio_referenced walks the anon_vma chain + * without the folio lock. Serialize against it with + * the anon_vma lock, the folio lock is not enough. + */ + src_anon_vma = folio_get_anon_vma(src_folio); + if (!src_anon_vma) { + /* page was unmapped from under us */ + err = -EAGAIN; + goto out; + } + if (!anon_vma_trylock_write(src_anon_vma)) { + pte_unmap(&orig_src_pte); + pte_unmap(&orig_dst_pte); + src_pte = dst_pte = NULL; + /* now we can block and wait */ + anon_vma_lock_write(src_anon_vma); + goto retry; + } + } + + err = move_present_pte(mm, dst_vma, src_vma, + dst_addr, src_addr, dst_pte, src_pte, + orig_dst_pte, orig_src_pte, + dst_ptl, src_ptl, src_folio); + } else { + entry = pte_to_swp_entry(orig_src_pte); + if (non_swap_entry(entry)) { + if (is_migration_entry(entry)) { + pte_unmap(&orig_src_pte); + pte_unmap(&orig_dst_pte); + src_pte = dst_pte = NULL; + migration_entry_wait(mm, src_pmd, src_addr); + err = -EAGAIN; + } else + err = -EFAULT; + goto out; + } + + err = move_swap_pte(mm, dst_addr, src_addr, + dst_pte, src_pte, + orig_dst_pte, orig_src_pte, + dst_ptl, src_ptl); + } + +out: + if (src_anon_vma) { + anon_vma_unlock_write(src_anon_vma); + put_anon_vma(src_anon_vma); + } + if (src_folio) { + folio_unlock(src_folio); + folio_put(src_folio); + } + if (dst_pte) + pte_unmap(dst_pte); + if (src_pte) + pte_unmap(src_pte); + mmu_notifier_invalidate_range_end(&range); + + return err; +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static inline bool move_splits_huge_pmd(unsigned long dst_addr, + unsigned long src_addr, + unsigned long src_end) +{ + return (src_addr & ~HPAGE_PMD_MASK) || (dst_addr & ~HPAGE_PMD_MASK) || + src_end - src_addr < HPAGE_PMD_SIZE; +} +#else +static inline bool move_splits_huge_pmd(unsigned long dst_addr, + unsigned long src_addr, + unsigned long src_end) +{ + /* This is unreachable anyway, just to avoid warnings when HPAGE_PMD_SIZE==0 */ + return false; +} +#endif + +static inline bool vma_move_compatible(struct vm_area_struct *vma) +{ + return !(vma->vm_flags & (VM_PFNMAP | VM_IO | VM_HUGETLB | + VM_MIXEDMAP | VM_SHADOW_STACK)); +} + +static int validate_move_areas(struct userfaultfd_ctx *ctx, + struct vm_area_struct *src_vma, + struct vm_area_struct *dst_vma) +{ + /* Only allow moving if both have the same access and protection */ + if ((src_vma->vm_flags & VM_ACCESS_FLAGS) != (dst_vma->vm_flags & VM_ACCESS_FLAGS) || + pgprot_val(src_vma->vm_page_prot) != pgprot_val(dst_vma->vm_page_prot)) + return -EINVAL; + + /* Only allow moving if both are mlocked or both aren't */ + if ((src_vma->vm_flags & VM_LOCKED) != (dst_vma->vm_flags & VM_LOCKED)) + return -EINVAL; + + /* + * For now, we keep it simple and only move between writable VMAs. + * Access flags are equal, therefore cheching only the source is enough. + */ + if (!(src_vma->vm_flags & VM_WRITE)) + return -EINVAL; + + /* Check if vma flags indicate content which can be moved */ + if (!vma_move_compatible(src_vma) || !vma_move_compatible(dst_vma)) + return -EINVAL; + + /* Ensure dst_vma is registered in uffd we are operating on */ + if (!dst_vma->vm_userfaultfd_ctx.ctx || + dst_vma->vm_userfaultfd_ctx.ctx != ctx) + return -EINVAL; + + /* Only allow moving across anonymous vmas */ + if (!vma_is_anonymous(src_vma) || !vma_is_anonymous(dst_vma)) + return -EINVAL; + + /* + * Ensure the dst_vma has a anon_vma or this page + * would get a NULL anon_vma when moved in the + * dst_vma. + */ + if (unlikely(anon_vma_prepare(dst_vma))) + return -ENOMEM; + + return 0; +} + +/** + * move_pages - move arbitrary anonymous pages of an existing vma + * @ctx: pointer to the userfaultfd context + * @mm: the address space to move pages + * @dst_start: start of the destination virtual memory range + * @src_start: start of the source virtual memory range + * @len: length of the virtual memory range + * @mode: flags from uffdio_move.mode + * + * Must be called with mmap_lock held for read. + * + * move_pages() remaps arbitrary anonymous pages atomically in zero + * copy. It only works on non shared anonymous pages because those can + * be relocated without generating non linear anon_vmas in the rmap + * code. + * + * It provides a zero copy mechanism to handle userspace page faults. + * The source vma pages should have mapcount == 1, which can be + * enforced by using madvise(MADV_DONTFORK) on src vma. + * + * The thread receiving the page during the userland page fault + * will receive the faulting page in the source vma through the network, + * storage or any other I/O device (MADV_DONTFORK in the source vma + * avoids move_pages() to fail with -EBUSY if the process forks before + * move_pages() is called), then it will call move_pages() to map the + * page in the faulting address in the destination vma. + * + * This userfaultfd command works purely via pagetables, so it's the + * most efficient way to move physical non shared anonymous pages + * across different virtual addresses. Unlike mremap()/mmap()/munmap() + * it does not create any new vmas. The mapping in the destination + * address is atomic. + * + * It only works if the vma protection bits are identical from the + * source and destination vma. + * + * It can remap non shared anonymous pages within the same vma too. + * + * If the source virtual memory range has any unmapped holes, or if + * the destination virtual memory range is not a whole unmapped hole, + * move_pages() will fail respectively with -ENOENT or -EEXIST. This + * provides a very strict behavior to avoid any chance of memory + * corruption going unnoticed if there are userland race conditions. + * Only one thread should resolve the userland page fault at any given + * time for any given faulting address. This means that if two threads + * try to both call move_pages() on the same destination address at the + * same time, the second thread will get an explicit error from this + * command. + * + * The command retval will return "len" is successful. The command + * however can be interrupted by fatal signals or errors. If + * interrupted it will return the number of bytes successfully + * remapped before the interruption if any, or the negative error if + * none. It will never return zero. Either it will return an error or + * an amount of bytes successfully moved. If the retval reports a + * "short" remap, the move_pages() command should be repeated by + * userland with src+retval, dst+reval, len-retval if it wants to know + * about the error that interrupted it. + * + * The UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES flag can be specified to + * prevent -ENOENT errors to materialize if there are holes in the + * source virtual range that is being remapped. The holes will be + * accounted as successfully remapped in the retval of the + * command. This is mostly useful to remap hugepage naturally aligned + * virtual regions without knowing if there are transparent hugepage + * in the regions or not, but preventing the risk of having to split + * the hugepmd during the remap. + * + * If there's any rmap walk that is taking the anon_vma locks without + * first obtaining the folio lock (the only current instance is + * folio_referenced), they will have to verify if the folio->mapping + * has changed after taking the anon_vma lock. If it changed they + * should release the lock and retry obtaining a new anon_vma, because + * it means the anon_vma was changed by move_pages() before the lock + * could be obtained. This is the only additional complexity added to + * the rmap code to provide this anonymous page remapping functionality. + */ +ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, + unsigned long dst_start, unsigned long src_start, + unsigned long len, __u64 mode) +{ + struct vm_area_struct *src_vma, *dst_vma; + unsigned long src_addr, dst_addr; + pmd_t *src_pmd, *dst_pmd; + long err = -EINVAL; + ssize_t moved = 0; + + /* Sanitize the command parameters. */ + if (WARN_ON_ONCE(src_start & ~PAGE_MASK) || + WARN_ON_ONCE(dst_start & ~PAGE_MASK) || + WARN_ON_ONCE(len & ~PAGE_MASK)) + goto out; + + /* Does the address range wrap, or is the span zero-sized? */ + if (WARN_ON_ONCE(src_start + len <= src_start) || + WARN_ON_ONCE(dst_start + len <= dst_start)) + goto out; + + /* + * Make sure the vma is not shared, that the src and dst remap + * ranges are both valid and fully within a single existing + * vma. + */ + src_vma = find_vma(mm, src_start); + if (!src_vma || (src_vma->vm_flags & VM_SHARED)) + goto out; + if (src_start < src_vma->vm_start || + src_start + len > src_vma->vm_end) + goto out; + + dst_vma = find_vma(mm, dst_start); + if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) + goto out; + if (dst_start < dst_vma->vm_start || + dst_start + len > dst_vma->vm_end) + goto out; + + err = validate_move_areas(ctx, src_vma, dst_vma); + if (err) + goto out; + + for (src_addr = src_start, dst_addr = dst_start; + src_addr < src_start + len;) { + spinlock_t *ptl; + pmd_t dst_pmdval; + unsigned long step_size; + + /* + * Below works because anonymous area would not have a + * transparent huge PUD. If file-backed support is added, + * that case would need to be handled here. + */ + src_pmd = mm_find_pmd(mm, src_addr); + if (unlikely(!src_pmd)) { + if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) { + err = -ENOENT; + break; + } + src_pmd = mm_alloc_pmd(mm, src_addr); + if (unlikely(!src_pmd)) { + err = -ENOMEM; + break; + } + } + dst_pmd = mm_alloc_pmd(mm, dst_addr); + if (unlikely(!dst_pmd)) { + err = -ENOMEM; + break; + } + + dst_pmdval = pmdp_get_lockless(dst_pmd); + /* + * If the dst_pmd is mapped as THP don't override it and just + * be strict. If dst_pmd changes into TPH after this check, the + * move_pages_huge_pmd() will detect the change and retry + * while move_pages_pte() will detect the change and fail. + */ + if (unlikely(pmd_trans_huge(dst_pmdval))) { + err = -EEXIST; + break; + } + + ptl = pmd_trans_huge_lock(src_pmd, src_vma); + if (ptl) { + if (pmd_devmap(*src_pmd)) { + spin_unlock(ptl); + err = -ENOENT; + break; + } + + /* Check if we can move the pmd without splitting it. */ + if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) || + !pmd_none(dst_pmdval)) { + struct folio *folio = pfn_folio(pmd_pfn(*src_pmd)); + + if (!folio || !PageAnonExclusive(&folio->page)) { + spin_unlock(ptl); + err = -EBUSY; + break; + } + + spin_unlock(ptl); + split_huge_pmd(src_vma, src_pmd, src_addr); + /* The folio will be split by move_pages_pte() */ + continue; + } + + err = move_pages_huge_pmd(mm, dst_pmd, src_pmd, + dst_pmdval, dst_vma, src_vma, + dst_addr, src_addr); + step_size = HPAGE_PMD_SIZE; + } else { + if (pmd_none(*src_pmd)) { + if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) { + err = -ENOENT; + break; + } + if (unlikely(__pte_alloc(mm, src_pmd))) { + err = -ENOMEM; + break; + } + } + + if (unlikely(pte_alloc(mm, dst_pmd))) { + err = -ENOMEM; + break; + } + + err = move_pages_pte(mm, dst_pmd, src_pmd, + dst_vma, src_vma, + dst_addr, src_addr, mode); + step_size = PAGE_SIZE; + } + + cond_resched(); + + if (fatal_signal_pending(current)) { + /* Do not override an error */ + if (!err || err == -EAGAIN) + err = -EINTR; + break; + } + + if (err) { + if (err == -EAGAIN) + continue; + break; + } + + /* Proceed to the next page */ + dst_addr += step_size; + src_addr += step_size; + moved += step_size; + } + +out: + VM_WARN_ON(moved < 0); + VM_WARN_ON(err > 0); + VM_WARN_ON(!moved && !err); + return moved ? moved : err; +}
+cc Alejandro
On Wed, Dec 06, 2023 at 02:36:56AM -0800, Suren Baghdasaryan wrote:
From: Andrea Arcangeli aarcange@redhat.com
Implement the uABI of UFFDIO_MOVE ioctl. UFFDIO_COPY performs ~20% better than UFFDIO_MOVE when the application needs pages to be allocated [1]. However, with UFFDIO_MOVE, if pages are available (in userspace) for recycling, as is usually the case in heap compaction algorithms, then we can avoid the page allocation and memcpy (done by UFFDIO_COPY). Also, since the pages are recycled in the userspace, we avoid the need to release (via madvise) the pages back to the kernel [2]. We see over 40% reduction (on a Google pixel 6 device) in the compacting thread’s completion time by using UFFDIO_MOVE vs. UFFDIO_COPY. This was measured using a benchmark that emulates a heap compaction implementation using userfaultfd (to allow concurrent accesses by application threads). More details of the usecase are explained in [2]. Furthermore, UFFDIO_MOVE enables moving swapped-out pages without touching them within the same vma. Today, it can only be done by mremap, however it forces splitting the vma.
[1] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redhat... [2] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyjn...
Update for the ioctl_userfaultfd(2) manpage:
Sorry to resurrect an old thread but... I don't think this update was ever propagated anywhere?
If you did send separately to man-pages list or whatnot maybe worth nudging again?
I don't see anything at [0].
[0]: https://man7.org/linux/man-pages/man2/ioctl_userfaultfd.2.html
Thanks!
UFFDIO_MOVE (Since Linux xxx) Move a continuous memory chunk into the userfault registered range and optionally wake up the blocked thread. The source and destination addresses and the number of bytes to move are specified by the src, dst, and len fields of the uffdio_move structure pointed to by argp:
struct uffdio_move { __u64 dst; /* Destination of move */ __u64 src; /* Source of move */ __u64 len; /* Number of bytes to move */ __u64 mode; /* Flags controlling behavior of move */ __s64 move; /* Number of bytes moved, or negated error */ }; The following value may be bitwise ORed in mode to change the behavior of the UFFDIO_MOVE operation: UFFDIO_MOVE_MODE_DONTWAKE Do not wake up the thread that waits for page-fault resolution UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES Allow holes in the source virtual range that is being moved. When not specified, the holes will result in ENOENT error. When specified, the holes will be accounted as successfully moved memory. This is mostly useful to move hugepage aligned virtual regions without knowing if there are transparent hugepages in the regions or not, but preventing the risk of having to split the hugepage during the operation. The move field is used by the kernel to return the number of bytes that was actually moved, or an error (a negated errno- style value). If the value returned in move doesn't match the value that was specified in len, the operation fails with the error EAGAIN. The move field is output-only; it is not read by the UFFDIO_MOVE operation. The operation may fail for various reasons. Usually, remapping of pages that are not exclusive to the given process fail; once KSM might deduplicate pages or fork() COW-shares pages during fork() with child processes, they are no longer exclusive. Further, the kernel might only perform lightweight checks for detecting whether the pages are exclusive, and return -EBUSY in case that check fails. To make the operation more likely to succeed, KSM should be disabled, fork() should be avoided or MADV_DONTFORK should be configured for the source VMA before fork(). This ioctl(2) operation returns 0 on success. In this case, the entire area was moved. On error, -1 is returned and errno is set to indicate the error. Possible errors include: EAGAIN The number of bytes moved (i.e., the value returned in the move field) does not equal the value that was specified in the len field. EINVAL Either dst or len was not a multiple of the system page size, or the range specified by src and len or dst and len was invalid. EINVAL An invalid bit was specified in the mode field. ENOENT The source virtual memory range has unmapped holes and UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES is not set. EEXIST The destination virtual memory range is fully or partially mapped. EBUSY The pages in the source virtual memory range are either pinned or not exclusive to the process. The kernel might only perform lightweight checks for detecting whether the pages are exclusive. To make the operation more likely to succeed, KSM should be disabled, fork() should be avoided or MADV_DONTFORK should be configured for the source virtual memory area before fork(). ENOMEM Allocating memory needed for the operation failed. ESRCH The target process has exited at the time of a UFFDIO_MOVE operation.Signed-off-by: Andrea Arcangeli aarcange@redhat.com Signed-off-by: Suren Baghdasaryan surenb@google.com
Documentation/admin-guide/mm/userfaultfd.rst | 3 + fs/userfaultfd.c | 72 +++ include/linux/rmap.h | 5 + include/linux/userfaultfd_k.h | 11 + include/uapi/linux/userfaultfd.h | 29 +- mm/huge_memory.c | 122 ++++ mm/khugepaged.c | 3 + mm/rmap.c | 6 + mm/userfaultfd.c | 614 +++++++++++++++++++ 9 files changed, 864 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 203e26da5f92..e5cc8848dcb3 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -113,6 +113,9 @@ events, except page fault notifications, may be generated: areas. ``UFFD_FEATURE_MINOR_SHMEM`` is the analogous feature indicating support for shmem virtual memory areas.
+- ``UFFD_FEATURE_MOVE`` indicates that the kernel supports moving an
- existing page contents from userspace.
The userland application should set the feature flags it intends to use when invoking the ``UFFDIO_API`` ioctl, to request that those features be enabled if supported. diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index e8af40b05549..6e2a4d6a0d8f 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -2005,6 +2005,75 @@ static inline unsigned int uffd_ctx_features(__u64 user_features) return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED; }
+static int userfaultfd_move(struct userfaultfd_ctx *ctx,
unsigned long arg)+{
- __s64 ret;
- struct uffdio_move uffdio_move;
- struct uffdio_move __user *user_uffdio_move;
- struct userfaultfd_wake_range range;
- struct mm_struct *mm = ctx->mm;
- user_uffdio_move = (struct uffdio_move __user *) arg;
- if (atomic_read(&ctx->mmap_changing))
return -EAGAIN;- if (copy_from_user(&uffdio_move, user_uffdio_move,
/* don't copy "move" last field */sizeof(uffdio_move)-sizeof(__s64)))return -EFAULT;- /* Do not allow cross-mm moves. */
- if (mm != current->mm)
return -EINVAL;- ret = validate_range(mm, uffdio_move.dst, uffdio_move.len);
- if (ret)
return ret;- ret = validate_range(mm, uffdio_move.src, uffdio_move.len);
- if (ret)
return ret;- if (uffdio_move.mode & ~(UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES|
UFFDIO_MOVE_MODE_DONTWAKE))return -EINVAL;- if (mmget_not_zero(mm)) {
mmap_read_lock(mm);/* Re-check after taking mmap_lock */if (likely(!atomic_read(&ctx->mmap_changing)))ret = move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src,uffdio_move.len, uffdio_move.mode);elseret = -EINVAL;mmap_read_unlock(mm);mmput(mm);- } else {
return -ESRCH;- }
- if (unlikely(put_user(ret, &user_uffdio_move->move)))
return -EFAULT;- if (ret < 0)
goto out;- /* len == 0 would wake all */
- VM_WARN_ON(!ret);
- range.len = ret;
- if (!(uffdio_move.mode & UFFDIO_MOVE_MODE_DONTWAKE)) {
range.start = uffdio_move.dst;wake_userfault(ctx, &range);- }
- ret = range.len == uffdio_move.len ? 0 : -EAGAIN;
+out:
- return ret;
+}
/*
- userland asks for a certain API version and we return which bits
- and ioctl commands are implemented in this kernel for such API
@@ -2097,6 +2166,9 @@ static long userfaultfd_ioctl(struct file *file, unsigned cmd, case UFFDIO_ZEROPAGE: ret = userfaultfd_zeropage(ctx, arg); break;
- case UFFDIO_MOVE:
ret = userfaultfd_move(ctx, arg);break;diff --git a/include/linux/rmap.h b/include/linux/rmap.h index b26fe858fd44..8034eda972e5 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -121,6 +121,11 @@ static inline void anon_vma_lock_write(struct anon_vma *anon_vma) down_write(&anon_vma->root->rwsem); }
+static inline int anon_vma_trylock_write(struct anon_vma *anon_vma) +{
- return down_write_trylock(&anon_vma->root->rwsem);
+}
static inline void anon_vma_unlock_write(struct anon_vma *anon_vma) { up_write(&anon_vma->root->rwsem); diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index f2dc19f40d05..e4056547fbe6 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -93,6 +93,17 @@ extern int mwriteprotect_range(struct mm_struct *dst_mm, extern long uffd_wp_range(struct vm_area_struct *vma, unsigned long start, unsigned long len, bool enable_wp);
+/* move_pages */ +void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2); +void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2); +ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm,
unsigned long dst_start, unsigned long src_start,unsigned long len, __u64 flags);+int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval,
struct vm_area_struct *dst_vma,struct vm_area_struct *src_vma,unsigned long dst_addr, unsigned long src_addr);/* mm helpers */ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, struct vm_userfaultfd_ctx vm_ctx) diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 0dbc81015018..2841e4ea8f2c 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -41,7 +41,8 @@ UFFD_FEATURE_WP_HUGETLBFS_SHMEM | \ UFFD_FEATURE_WP_UNPOPULATED | \ UFFD_FEATURE_POISON | \
UFFD_FEATURE_WP_ASYNC)
UFFD_FEATURE_WP_ASYNC | \UFFD_FEATURE_MOVE)#define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -50,6 +51,7 @@ ((__u64)1 << _UFFDIO_WAKE | \ (__u64)1 << _UFFDIO_COPY | \ (__u64)1 << _UFFDIO_ZEROPAGE | \
(__u64)1 << _UFFDIO_MOVE | \@@ -73,6 +75,7 @@ #define _UFFDIO_WAKE (0x02) #define _UFFDIO_COPY (0x03) #define _UFFDIO_ZEROPAGE (0x04) +#define _UFFDIO_MOVE (0x05) #define _UFFDIO_WRITEPROTECT (0x06) #define _UFFDIO_CONTINUE (0x07) #define _UFFDIO_POISON (0x08) @@ -92,6 +95,8 @@ struct uffdio_copy) #define UFFDIO_ZEROPAGE _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \ struct uffdio_zeropage) +#define UFFDIO_MOVE _IOWR(UFFDIO, _UFFDIO_MOVE, \
struct uffdio_move)#define UFFDIO_WRITEPROTECT _IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \ struct uffdio_writeprotect) #define UFFDIO_CONTINUE _IOWR(UFFDIO, _UFFDIO_CONTINUE, \ @@ -222,6 +227,9 @@ struct uffdio_api { * asynchronous mode is supported in which the write fault is * automatically resolved and write-protection is un-set. * It implies UFFD_FEATURE_WP_UNPOPULATED.
** UFFD_FEATURE_MOVE indicates that the kernel supports moving an* existing page contents from userspace.#define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) @@ -239,6 +247,7 @@ struct uffdio_api { #define UFFD_FEATURE_WP_UNPOPULATED (1<<13) #define UFFD_FEATURE_POISON (1<<14) #define UFFD_FEATURE_WP_ASYNC (1<<15) +#define UFFD_FEATURE_MOVE (1<<16) __u64 features;
__u64 ioctls; @@ -347,6 +356,24 @@ struct uffdio_poison { __s64 updated; };
+struct uffdio_move {
- __u64 dst;
- __u64 src;
- __u64 len;
- /*
* Especially if used to atomically remove memory from the* address space the wake on the dst range is not needed.*/+#define UFFDIO_MOVE_MODE_DONTWAKE ((__u64)1<<0) +#define UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES ((__u64)1<<1)
- __u64 mode;
- /*
* "move" is written by the ioctl and must be at the end: the* copy_from_user will not read the last 8 bytes.*/- __s64 move;
+};
/*
- Flags for the userfaultfd(2) system call itself.
*/ diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 4f542444a91f..315968db1ca4 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1964,6 +1964,128 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, return ret; }
+#ifdef CONFIG_USERFAULTFD +/*
- The PT lock for src_pmd and the mmap_lock for reading are held by
- the caller, but it must return after releasing the page_table_lock.
- Just move the page from src_pmd to dst_pmd if possible.
- Return zero if succeeded in moving the page, -EAGAIN if it needs to be
- repeated by the caller, or other errors in case of failure.
- */
+int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval,
struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,unsigned long dst_addr, unsigned long src_addr)+{
- pmd_t _dst_pmd, src_pmdval;
- struct page *src_page;
- struct folio *src_folio;
- struct anon_vma *src_anon_vma;
- spinlock_t *src_ptl, *dst_ptl;
- pgtable_t src_pgtable;
- struct mmu_notifier_range range;
- int err = 0;
- src_pmdval = *src_pmd;
- src_ptl = pmd_lockptr(mm, src_pmd);
- lockdep_assert_held(src_ptl);
- mmap_assert_locked(mm);
- /* Sanity checks before the operation */
- if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE_PMD_MASK) ||
WARN_ON_ONCE(dst_addr & ~HPAGE_PMD_MASK)) {spin_unlock(src_ptl);return -EINVAL;- }
- if (!pmd_trans_huge(src_pmdval)) {
spin_unlock(src_ptl);if (is_pmd_migration_entry(src_pmdval)) {pmd_migration_entry_wait(mm, &src_pmdval);return -EAGAIN;}return -ENOENT;- }
- src_page = pmd_page(src_pmdval);
- if (unlikely(!PageAnonExclusive(src_page))) {
spin_unlock(src_ptl);return -EBUSY;- }
- src_folio = page_folio(src_page);
- folio_get(src_folio);
- spin_unlock(src_ptl);
- flush_cache_range(src_vma, src_addr, src_addr + HPAGE_PMD_SIZE);
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, src_addr,
src_addr + HPAGE_PMD_SIZE);- mmu_notifier_invalidate_range_start(&range);
- folio_lock(src_folio);
- /*
* split_huge_page walks the anon_vma chain without the page* lock. Serialize against it with the anon_vma lock, the page* lock is not enough.*/- src_anon_vma = folio_get_anon_vma(src_folio);
- if (!src_anon_vma) {
err = -EAGAIN;goto unlock_folio;- }
- anon_vma_lock_write(src_anon_vma);
- dst_ptl = pmd_lockptr(mm, dst_pmd);
- double_pt_lock(src_ptl, dst_ptl);
- if (unlikely(!pmd_same(*src_pmd, src_pmdval) ||
!pmd_same(*dst_pmd, dst_pmdval))) {err = -EAGAIN;goto unlock_ptls;- }
- if (folio_maybe_dma_pinned(src_folio) ||
!PageAnonExclusive(&src_folio->page)) {err = -EBUSY;goto unlock_ptls;- }
- if (WARN_ON_ONCE(!folio_test_head(src_folio)) ||
WARN_ON_ONCE(!folio_test_anon(src_folio))) {err = -EBUSY;goto unlock_ptls;- }
- folio_move_anon_rmap(src_folio, dst_vma);
- WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
- src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
- /* Folio got pinned from under us. Put it back and fail the move. */
- if (folio_maybe_dma_pinned(src_folio)) {
set_pmd_at(mm, src_addr, src_pmd, src_pmdval);err = -EBUSY;goto unlock_ptls;- }
- _dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot);
- /* Follow mremap() behavior and treat the entry dirty after the move */
- _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma);
- set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd);
- src_pgtable = pgtable_trans_huge_withdraw(mm, src_pmd);
- pgtable_trans_huge_deposit(mm, dst_pmd, src_pgtable);
+unlock_ptls:
- double_pt_unlock(src_ptl, dst_ptl);
- anon_vma_unlock_write(src_anon_vma);
- put_anon_vma(src_anon_vma);
+unlock_folio:
- /* unblock rmap walks */
- folio_unlock(src_folio);
- mmu_notifier_invalidate_range_end(&range);
- folio_put(src_folio);
- return err;
+} +#endif /* CONFIG_USERFAULTFD */
/*
- Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 064654717843..0da6937572cf 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1139,6 +1139,9 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, * Prevent all access to pagetables with the exception of * gup_fast later handled by the ptep_clear_flush and the VM * handled by the anon_vma lock + PG_lock.
** UFFDIO_MOVE is prevented to race as well thanks to the* mmap_lock.diff --git a/mm/rmap.c b/mm/rmap.c index 525c5bc0b0b3..de9426ad0f1b 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -490,6 +490,12 @@ void __init anon_vma_init(void)
- page_remove_rmap() that the anon_vma pointer from page->mapping is valid
- if there is a mapcount, we can dereference the anon_vma after observing
- those.
- NOTE: the caller should normally hold folio lock when calling this. If
- not, the caller needs to double check the anon_vma didn't change after
- taking the anon_vma lock for either read or write (UFFDIO_MOVE can modify it
- concurrently without folio lock protection). See folio_lock_anon_vma_read()
*/
- which has already covered that, and comment above remap_pages().
struct anon_vma *folio_get_anon_vma(struct folio *folio) { diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 0b6ca553bebe..9ec814e47e99 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -842,3 +842,617 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, mmap_read_unlock(dst_mm); return err; }
+void double_pt_lock(spinlock_t *ptl1,
spinlock_t *ptl2)- __acquires(ptl1)
- __acquires(ptl2)
+{
- spinlock_t *ptl_tmp;
- if (ptl1 > ptl2) {
/* exchange ptl1 and ptl2 */ptl_tmp = ptl1;ptl1 = ptl2;ptl2 = ptl_tmp;- }
- /* lock in virtual address order to avoid lock inversion */
- spin_lock(ptl1);
- if (ptl1 != ptl2)
spin_lock_nested(ptl2, SINGLE_DEPTH_NESTING);- else
__acquire(ptl2);+}
+void double_pt_unlock(spinlock_t *ptl1,
spinlock_t *ptl2)- __releases(ptl1)
- __releases(ptl2)
+{
- spin_unlock(ptl1);
- if (ptl1 != ptl2)
spin_unlock(ptl2);- else
__release(ptl2);+}
+static int move_present_pte(struct mm_struct *mm,
struct vm_area_struct *dst_vma,struct vm_area_struct *src_vma,unsigned long dst_addr, unsigned long src_addr,pte_t *dst_pte, pte_t *src_pte,pte_t orig_dst_pte, pte_t orig_src_pte,spinlock_t *dst_ptl, spinlock_t *src_ptl,struct folio *src_folio)+{
- int err = 0;
- double_pt_lock(dst_ptl, src_ptl);
- if (!pte_same(*src_pte, orig_src_pte) ||
!pte_same(*dst_pte, orig_dst_pte)) {err = -EAGAIN;goto out;- }
- if (folio_test_large(src_folio) ||
folio_maybe_dma_pinned(src_folio) ||!PageAnonExclusive(&src_folio->page)) {err = -EBUSY;goto out;- }
- folio_move_anon_rmap(src_folio, dst_vma);
- WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
- orig_src_pte = ptep_clear_flush(src_vma, src_addr, src_pte);
- /* Folio got pinned from under us. Put it back and fail the move. */
- if (folio_maybe_dma_pinned(src_folio)) {
set_pte_at(mm, src_addr, src_pte, orig_src_pte);err = -EBUSY;goto out;- }
- orig_dst_pte = mk_pte(&src_folio->page, dst_vma->vm_page_prot);
- /* Follow mremap() behavior and treat the entry dirty after the move */
- orig_dst_pte = pte_mkwrite(pte_mkdirty(orig_dst_pte), dst_vma);
- set_pte_at(mm, dst_addr, dst_pte, orig_dst_pte);
+out:
- double_pt_unlock(dst_ptl, src_ptl);
- return err;
+}
+static int move_swap_pte(struct mm_struct *mm,
unsigned long dst_addr, unsigned long src_addr,pte_t *dst_pte, pte_t *src_pte,pte_t orig_dst_pte, pte_t orig_src_pte,spinlock_t *dst_ptl, spinlock_t *src_ptl)+{
- if (!pte_swp_exclusive(orig_src_pte))
return -EBUSY;- double_pt_lock(dst_ptl, src_ptl);
- if (!pte_same(*src_pte, orig_src_pte) ||
!pte_same(*dst_pte, orig_dst_pte)) {double_pt_unlock(dst_ptl, src_ptl);return -EAGAIN;- }
- orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte);
- set_pte_at(mm, dst_addr, dst_pte, orig_src_pte);
- double_pt_unlock(dst_ptl, src_ptl);
- return 0;
+}
+/*
- The mmap_lock for reading is held by the caller. Just move the page
- from src_pmd to dst_pmd if possible, and return true if succeeded
- in moving the page.
- */
+static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd,
struct vm_area_struct *dst_vma,struct vm_area_struct *src_vma,unsigned long dst_addr, unsigned long src_addr,__u64 mode)+{
- swp_entry_t entry;
- pte_t orig_src_pte, orig_dst_pte;
- pte_t src_folio_pte;
- spinlock_t *src_ptl, *dst_ptl;
- pte_t *src_pte = NULL;
- pte_t *dst_pte = NULL;
- struct folio *src_folio = NULL;
- struct anon_vma *src_anon_vma = NULL;
- struct mmu_notifier_range range;
- int err = 0;
- flush_cache_range(src_vma, src_addr, src_addr + PAGE_SIZE);
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
src_addr, src_addr + PAGE_SIZE);- mmu_notifier_invalidate_range_start(&range);
+retry:
- dst_pte = pte_offset_map_nolock(mm, dst_pmd, dst_addr, &dst_ptl);
- /* Retry if a huge pmd materialized from under us */
- if (unlikely(!dst_pte)) {
err = -EAGAIN;goto out;- }
- src_pte = pte_offset_map_nolock(mm, src_pmd, src_addr, &src_ptl);
- /*
* We held the mmap_lock for reading so MADV_DONTNEED* can zap transparent huge pages under us, or the* transparent huge page fault can establish new* transparent huge pages under us.*/- if (unlikely(!src_pte)) {
err = -EAGAIN;goto out;- }
- /* Sanity checks before the operation */
- if (WARN_ON_ONCE(pmd_none(*dst_pmd)) || WARN_ON_ONCE(pmd_none(*src_pmd)) ||
WARN_ON_ONCE(pmd_trans_huge(*dst_pmd)) || WARN_ON_ONCE(pmd_trans_huge(*src_pmd))) {err = -EINVAL;goto out;- }
- spin_lock(dst_ptl);
- orig_dst_pte = *dst_pte;
- spin_unlock(dst_ptl);
- if (!pte_none(orig_dst_pte)) {
err = -EEXIST;goto out;- }
- spin_lock(src_ptl);
- orig_src_pte = *src_pte;
- spin_unlock(src_ptl);
- if (pte_none(orig_src_pte)) {
if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES))err = -ENOENT;else /* nothing to do to move a hole */err = 0;goto out;- }
- /* If PTE changed after we locked the folio them start over */
- if (src_folio && unlikely(!pte_same(src_folio_pte, orig_src_pte))) {
err = -EAGAIN;goto out;- }
- if (pte_present(orig_src_pte)) {
/** Pin and lock both source folio and anon_vma. Since we are in* RCU read section, we can't block, so on contention have to* unmap the ptes, obtain the lock and retry.*/if (!src_folio) {struct folio *folio;/** Pin the page while holding the lock to be sure the* page isn't freed under us*/spin_lock(src_ptl);if (!pte_same(orig_src_pte, *src_pte)) {spin_unlock(src_ptl);err = -EAGAIN;goto out;}folio = vm_normal_folio(src_vma, src_addr, orig_src_pte);if (!folio || !PageAnonExclusive(&folio->page)) {spin_unlock(src_ptl);err = -EBUSY;goto out;}folio_get(folio);src_folio = folio;src_folio_pte = orig_src_pte;spin_unlock(src_ptl);if (!folio_trylock(src_folio)) {pte_unmap(&orig_src_pte);pte_unmap(&orig_dst_pte);src_pte = dst_pte = NULL;/* now we can block and wait */folio_lock(src_folio);goto retry;}if (WARN_ON_ONCE(!folio_test_anon(src_folio))) {err = -EBUSY;goto out;}}/* at this point we have src_folio locked */if (folio_test_large(src_folio)) {err = split_folio(src_folio);if (err)goto out;}if (!src_anon_vma) {/** folio_referenced walks the anon_vma chain* without the folio lock. Serialize against it with* the anon_vma lock, the folio lock is not enough.*/src_anon_vma = folio_get_anon_vma(src_folio);if (!src_anon_vma) {/* page was unmapped from under us */err = -EAGAIN;goto out;}if (!anon_vma_trylock_write(src_anon_vma)) {pte_unmap(&orig_src_pte);pte_unmap(&orig_dst_pte);src_pte = dst_pte = NULL;/* now we can block and wait */anon_vma_lock_write(src_anon_vma);goto retry;}}err = move_present_pte(mm, dst_vma, src_vma,dst_addr, src_addr, dst_pte, src_pte,orig_dst_pte, orig_src_pte,dst_ptl, src_ptl, src_folio);- } else {
entry = pte_to_swp_entry(orig_src_pte);if (non_swap_entry(entry)) {if (is_migration_entry(entry)) {pte_unmap(&orig_src_pte);pte_unmap(&orig_dst_pte);src_pte = dst_pte = NULL;migration_entry_wait(mm, src_pmd, src_addr);err = -EAGAIN;} elseerr = -EFAULT;goto out;}err = move_swap_pte(mm, dst_addr, src_addr,dst_pte, src_pte,orig_dst_pte, orig_src_pte,dst_ptl, src_ptl);- }
+out:
- if (src_anon_vma) {
anon_vma_unlock_write(src_anon_vma);put_anon_vma(src_anon_vma);- }
- if (src_folio) {
folio_unlock(src_folio);folio_put(src_folio);- }
- if (dst_pte)
pte_unmap(dst_pte);- if (src_pte)
pte_unmap(src_pte);- mmu_notifier_invalidate_range_end(&range);
- return err;
+}
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static inline bool move_splits_huge_pmd(unsigned long dst_addr,
unsigned long src_addr,unsigned long src_end)+{
- return (src_addr & ~HPAGE_PMD_MASK) || (dst_addr & ~HPAGE_PMD_MASK) ||
src_end - src_addr < HPAGE_PMD_SIZE;+} +#else +static inline bool move_splits_huge_pmd(unsigned long dst_addr,
unsigned long src_addr,unsigned long src_end)+{
- /* This is unreachable anyway, just to avoid warnings when HPAGE_PMD_SIZE==0 */
- return false;
+} +#endif
+static inline bool vma_move_compatible(struct vm_area_struct *vma) +{
- return !(vma->vm_flags & (VM_PFNMAP | VM_IO | VM_HUGETLB |
VM_MIXEDMAP | VM_SHADOW_STACK));+}
+static int validate_move_areas(struct userfaultfd_ctx *ctx,
struct vm_area_struct *src_vma,struct vm_area_struct *dst_vma)+{
- /* Only allow moving if both have the same access and protection */
- if ((src_vma->vm_flags & VM_ACCESS_FLAGS) != (dst_vma->vm_flags & VM_ACCESS_FLAGS) ||
pgprot_val(src_vma->vm_page_prot) != pgprot_val(dst_vma->vm_page_prot))return -EINVAL;- /* Only allow moving if both are mlocked or both aren't */
- if ((src_vma->vm_flags & VM_LOCKED) != (dst_vma->vm_flags & VM_LOCKED))
return -EINVAL;- /*
* For now, we keep it simple and only move between writable VMAs.* Access flags are equal, therefore cheching only the source is enough.*/- if (!(src_vma->vm_flags & VM_WRITE))
return -EINVAL;- /* Check if vma flags indicate content which can be moved */
- if (!vma_move_compatible(src_vma) || !vma_move_compatible(dst_vma))
return -EINVAL;- /* Ensure dst_vma is registered in uffd we are operating on */
- if (!dst_vma->vm_userfaultfd_ctx.ctx ||
dst_vma->vm_userfaultfd_ctx.ctx != ctx)return -EINVAL;- /* Only allow moving across anonymous vmas */
- if (!vma_is_anonymous(src_vma) || !vma_is_anonymous(dst_vma))
return -EINVAL;- /*
* Ensure the dst_vma has a anon_vma or this page* would get a NULL anon_vma when moved in the* dst_vma.*/- if (unlikely(anon_vma_prepare(dst_vma)))
return -ENOMEM;- return 0;
+}
+/**
- move_pages - move arbitrary anonymous pages of an existing vma
- @ctx: pointer to the userfaultfd context
- @mm: the address space to move pages
- @dst_start: start of the destination virtual memory range
- @src_start: start of the source virtual memory range
- @len: length of the virtual memory range
- @mode: flags from uffdio_move.mode
- Must be called with mmap_lock held for read.
- move_pages() remaps arbitrary anonymous pages atomically in zero
- copy. It only works on non shared anonymous pages because those can
- be relocated without generating non linear anon_vmas in the rmap
- code.
- It provides a zero copy mechanism to handle userspace page faults.
- The source vma pages should have mapcount == 1, which can be
- enforced by using madvise(MADV_DONTFORK) on src vma.
- The thread receiving the page during the userland page fault
- will receive the faulting page in the source vma through the network,
- storage or any other I/O device (MADV_DONTFORK in the source vma
- avoids move_pages() to fail with -EBUSY if the process forks before
- move_pages() is called), then it will call move_pages() to map the
- page in the faulting address in the destination vma.
- This userfaultfd command works purely via pagetables, so it's the
- most efficient way to move physical non shared anonymous pages
- across different virtual addresses. Unlike mremap()/mmap()/munmap()
- it does not create any new vmas. The mapping in the destination
- address is atomic.
- It only works if the vma protection bits are identical from the
- source and destination vma.
- It can remap non shared anonymous pages within the same vma too.
- If the source virtual memory range has any unmapped holes, or if
- the destination virtual memory range is not a whole unmapped hole,
- move_pages() will fail respectively with -ENOENT or -EEXIST. This
- provides a very strict behavior to avoid any chance of memory
- corruption going unnoticed if there are userland race conditions.
- Only one thread should resolve the userland page fault at any given
- time for any given faulting address. This means that if two threads
- try to both call move_pages() on the same destination address at the
- same time, the second thread will get an explicit error from this
- command.
- The command retval will return "len" is successful. The command
- however can be interrupted by fatal signals or errors. If
- interrupted it will return the number of bytes successfully
- remapped before the interruption if any, or the negative error if
- none. It will never return zero. Either it will return an error or
- an amount of bytes successfully moved. If the retval reports a
- "short" remap, the move_pages() command should be repeated by
- userland with src+retval, dst+reval, len-retval if it wants to know
- about the error that interrupted it.
- The UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES flag can be specified to
- prevent -ENOENT errors to materialize if there are holes in the
- source virtual range that is being remapped. The holes will be
- accounted as successfully remapped in the retval of the
- command. This is mostly useful to remap hugepage naturally aligned
- virtual regions without knowing if there are transparent hugepage
- in the regions or not, but preventing the risk of having to split
- the hugepmd during the remap.
- If there's any rmap walk that is taking the anon_vma locks without
- first obtaining the folio lock (the only current instance is
- folio_referenced), they will have to verify if the folio->mapping
- has changed after taking the anon_vma lock. If it changed they
- should release the lock and retry obtaining a new anon_vma, because
- it means the anon_vma was changed by move_pages() before the lock
- could be obtained. This is the only additional complexity added to
- the rmap code to provide this anonymous page remapping functionality.
- */
+ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm,
unsigned long dst_start, unsigned long src_start,unsigned long len, __u64 mode)+{
- struct vm_area_struct *src_vma, *dst_vma;
- unsigned long src_addr, dst_addr;
- pmd_t *src_pmd, *dst_pmd;
- long err = -EINVAL;
- ssize_t moved = 0;
- /* Sanitize the command parameters. */
- if (WARN_ON_ONCE(src_start & ~PAGE_MASK) ||
WARN_ON_ONCE(dst_start & ~PAGE_MASK) ||WARN_ON_ONCE(len & ~PAGE_MASK))goto out;- /* Does the address range wrap, or is the span zero-sized? */
- if (WARN_ON_ONCE(src_start + len <= src_start) ||
WARN_ON_ONCE(dst_start + len <= dst_start))goto out;- /*
* Make sure the vma is not shared, that the src and dst remap* ranges are both valid and fully within a single existing* vma.*/- src_vma = find_vma(mm, src_start);
- if (!src_vma || (src_vma->vm_flags & VM_SHARED))
goto out;- if (src_start < src_vma->vm_start ||
src_start + len > src_vma->vm_end)goto out;- dst_vma = find_vma(mm, dst_start);
- if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
goto out;- if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)goto out;- err = validate_move_areas(ctx, src_vma, dst_vma);
- if (err)
goto out;- for (src_addr = src_start, dst_addr = dst_start;
src_addr < src_start + len;) {spinlock_t *ptl;pmd_t dst_pmdval;unsigned long step_size;/** Below works because anonymous area would not have a* transparent huge PUD. If file-backed support is added,* that case would need to be handled here.*/src_pmd = mm_find_pmd(mm, src_addr);if (unlikely(!src_pmd)) {if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) {err = -ENOENT;break;}src_pmd = mm_alloc_pmd(mm, src_addr);if (unlikely(!src_pmd)) {err = -ENOMEM;break;}}dst_pmd = mm_alloc_pmd(mm, dst_addr);if (unlikely(!dst_pmd)) {err = -ENOMEM;break;}dst_pmdval = pmdp_get_lockless(dst_pmd);/** If the dst_pmd is mapped as THP don't override it and just* be strict. If dst_pmd changes into TPH after this check, the* move_pages_huge_pmd() will detect the change and retry* while move_pages_pte() will detect the change and fail.*/if (unlikely(pmd_trans_huge(dst_pmdval))) {err = -EEXIST;break;}ptl = pmd_trans_huge_lock(src_pmd, src_vma);if (ptl) {if (pmd_devmap(*src_pmd)) {spin_unlock(ptl);err = -ENOENT;break;}/* Check if we can move the pmd without splitting it. */if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) ||!pmd_none(dst_pmdval)) {struct folio *folio = pfn_folio(pmd_pfn(*src_pmd));if (!folio || !PageAnonExclusive(&folio->page)) {spin_unlock(ptl);err = -EBUSY;break;}spin_unlock(ptl);split_huge_pmd(src_vma, src_pmd, src_addr);/* The folio will be split by move_pages_pte() */continue;}err = move_pages_huge_pmd(mm, dst_pmd, src_pmd,dst_pmdval, dst_vma, src_vma,dst_addr, src_addr);step_size = HPAGE_PMD_SIZE;} else {if (pmd_none(*src_pmd)) {if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) {err = -ENOENT;break;}if (unlikely(__pte_alloc(mm, src_pmd))) {err = -ENOMEM;break;}}if (unlikely(pte_alloc(mm, dst_pmd))) {err = -ENOMEM;break;}err = move_pages_pte(mm, dst_pmd, src_pmd,dst_vma, src_vma,dst_addr, src_addr, mode);step_size = PAGE_SIZE;}cond_resched();if (fatal_signal_pending(current)) {/* Do not override an error */if (!err || err == -EAGAIN)err = -EINTR;break;}if (err) {if (err == -EAGAIN)continue;break;}/* Proceed to the next page */dst_addr += step_size;src_addr += step_size;moved += step_size;- }
+out:
- VM_WARN_ON(moved < 0);
- VM_WARN_ON(err > 0);
- VM_WARN_ON(!moved && !err);
- return moved ? moved : err;
+}
2.43.0.rc2.451.g8631bc7472-goog
Hi Lorenzo, Suren, Andrea,
On Sat, Apr 19, 2025 at 07:57:36PM +0100, Lorenzo Stoakes wrote:
+cc Alejandro
Thanks!
On Wed, Dec 06, 2023 at 02:36:56AM -0800, Suren Baghdasaryan wrote:
From: Andrea Arcangeli aarcange@redhat.com
Implement the uABI of UFFDIO_MOVE ioctl.
[...]
[1] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redhat... [2] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyjn...
Update for the ioctl_userfaultfd(2) manpage:
Sorry to resurrect an old thread but... I don't think this update was ever propagated anywhere?
If you did send separately to man-pages list or whatnot maybe worth nudging again?
I don't see anything at [0].
Thanks!
UFFDIO_MOVE (Since Linux xxx) Move a continuous memory chunk into the
Nope, it seems this was never sent to linux-man@. https://lore.kernel.org/linux-man/?q=UFFDIO_MOVE:
[No results found]
Please re-send including linux-man@ in CC, as specified in https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING
Have a lovely night! Alex
On Sat, Apr 19, 2025 at 12:26 PM Alejandro Colomar alx@kernel.org wrote:
Hi Lorenzo, Suren, Andrea,
On Sat, Apr 19, 2025 at 07:57:36PM +0100, Lorenzo Stoakes wrote:
+cc Alejandro
Thanks!
On Wed, Dec 06, 2023 at 02:36:56AM -0800, Suren Baghdasaryan wrote:
From: Andrea Arcangeli aarcange@redhat.com
Implement the uABI of UFFDIO_MOVE ioctl.
[...]
[1] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redhat... [2] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyjn...
Update for the ioctl_userfaultfd(2) manpage:
Sorry to resurrect an old thread but... I don't think this update was ever propagated anywhere?
If you did send separately to man-pages list or whatnot maybe worth nudging again?
I don't see anything at [0].
Thanks for bringing it up! This must have slipped from my attention.
Thanks!
UFFDIO_MOVE (Since Linux xxx) Move a continuous memory chunk into the
Nope, it seems this was never sent to linux-man@. https://lore.kernel.org/linux-man/?q=UFFDIO_MOVE:
Sorry for missing that part.
[No results found]Please re-send including linux-man@ in CC, as specified in https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING
Thanks for the reference. Will post the documentation update later today. Thanks, Suren.
Have a lovely night! Alex
On Mon, Apr 21, 2025 at 10:16 AM Suren Baghdasaryan surenb@google.com wrote:
On Sat, Apr 19, 2025 at 12:26 PM Alejandro Colomar alx@kernel.org wrote:
Hi Lorenzo, Suren, Andrea,
On Sat, Apr 19, 2025 at 07:57:36PM +0100, Lorenzo Stoakes wrote:
+cc Alejandro
Thanks!
On Wed, Dec 06, 2023 at 02:36:56AM -0800, Suren Baghdasaryan wrote:
From: Andrea Arcangeli aarcange@redhat.com
Implement the uABI of UFFDIO_MOVE ioctl.
[...]
[1] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redhat... [2] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyjn...
Update for the ioctl_userfaultfd(2) manpage:
Sorry to resurrect an old thread but... I don't think this update was ever propagated anywhere?
If you did send separately to man-pages list or whatnot maybe worth nudging again?
I don't see anything at [0].
Thanks for bringing it up! This must have slipped from my attention.
Thanks!
UFFDIO_MOVE (Since Linux xxx) Move a continuous memory chunk into the
Nope, it seems this was never sent to linux-man@. https://lore.kernel.org/linux-man/?q=UFFDIO_MOVE:
Sorry for missing that part.
[No results found]Please re-send including linux-man@ in CC, as specified in https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING
Thanks for the reference. Will post the documentation update later today.
Was planning to post today but I'm a bit rusty with the syntax. Will try to send it out tomorrow after verifying the results.
Thanks, Suren.
Have a lovely night! Alex
Hi Suren,
On Mon, Apr 21, 2025 at 08:58:22PM -0700, Suren Baghdasaryan wrote:
Please re-send including linux-man@ in CC, as specified in https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING
Thanks for the reference. Will post the documentation update later today.
Was planning to post today but I'm a bit rusty with the syntax. Will try to send it out tomorrow
No problem.
after verifying the results.
For verifying, you might want to try diffman-git(1). It's provided in the man-pages repo. If the version of the man-pages package provided by your distro is >=6.10, you may already have it in your system, and if not, you can find it as <src/bin/diffman-git> in the repo. It's documented in a manual page in the same repo, of course.
I don't know if you know about the build system, which also checks a few common issues in the pages. You can check <CONTRIBUTING.d/lint>. TL;DR:
$ make -R -j8 -k lint-man build-all check;
(You can ignore anything that's not about the page you're modifying. At the moment, I see a few issues that I'll need to investigate in a few pages. For seeing a clean list of what's failing, you can ignore stderr; see below.)
$ make -R -j24 -k lint-man build-all check 2>/dev/null TROFF .tmp/man/man2/statx.2.cat.set TROFF .tmp/man/man2const/KEYCTL_SETPERM.2const.html.set TROFF .tmp/man/man2const/KEYCTL_SETPERM.2const.pdf.set TROFF .tmp/man/man2const/KEYCTL_SETPERM.2const.ps.set GREP .tmp/man/man2/pipe.2.check-catman.touch GREP .tmp/man/man3/ctime.3.check-catman.touch GREP .tmp/man/man7/landlock.7.check-catman.touch GREP .tmp/man/man7/rtnetlink.7.check-catman.touch
Have a lovely day! Alex
On Tue, Apr 22, 2025 at 12:20 AM Alejandro Colomar alx@kernel.org wrote:
Hi Suren,
On Mon, Apr 21, 2025 at 08:58:22PM -0700, Suren Baghdasaryan wrote:
Please re-send including linux-man@ in CC, as specified in https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING
Thanks for the reference. Will post the documentation update later today.
Was planning to post today but I'm a bit rusty with the syntax. Will try to send it out tomorrow
No problem.
after verifying the results.
For verifying, you might want to try diffman-git(1). It's provided in the man-pages repo. If the version of the man-pages package provided by your distro is >=6.10, you may already have it in your system, and if not, you can find it as <src/bin/diffman-git> in the repo. It's documented in a manual page in the same repo, of course.
I don't know if you know about the build system, which also checks a few common issues in the pages. You can check <CONTRIBUTING.d/lint>. TL;DR:
$ make -R -j8 -k lint-man build-all check;(You can ignore anything that's not about the page you're modifying. At the moment, I see a few issues that I'll need to investigate in a few pages. For seeing a clean list of what's failing, you can ignore stderr; see below.)
$ make -R -j24 -k lint-man build-all check 2>/dev/null TROFF .tmp/man/man2/statx.2.cat.set TROFF .tmp/man/man2const/KEYCTL_SETPERM.2const.html.set TROFF .tmp/man/man2const/KEYCTL_SETPERM.2const.pdf.set TROFF .tmp/man/man2const/KEYCTL_SETPERM.2const.ps.set GREP .tmp/man/man2/pipe.2.check-catman.touch GREP .tmp/man/man3/ctime.3.check-catman.touch GREP .tmp/man/man7/landlock.7.check-catman.touch GREP .tmp/man/man7/rtnetlink.7.check-catman.touch
Thanks for the detailed instructions, Alex! Posted the patch at https://lore.kernel.org/all/20250423011203.2559210-1-surenb@google.com/ and hopefully I did not miss something important. Cheers, Suren.
Have a lovely day! Alex
uffd_test_ctx_clear() is being called from uffd_test_ctx_init() to unmap areas used in the previous test run. This approach is problematic because while unmapping areas uffd_test_ctx_clear() uses page_size and nr_pages which might differ from one test run to another. Fix this by calling uffd_test_ctx_clear() after each test is done.
Signed-off-by: Suren Baghdasaryan surenb@google.com Reviewed-by: Peter Xu peterx@redhat.com Reviewed-by: Axel Rasmussen axelrasmussen@google.com --- tools/testing/selftests/mm/uffd-common.c | 4 +--- tools/testing/selftests/mm/uffd-common.h | 1 + tools/testing/selftests/mm/uffd-stress.c | 5 ++++- tools/testing/selftests/mm/uffd-unit-tests.c | 1 + 4 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c index 02b89860e193..583e5a4cc0fd 100644 --- a/tools/testing/selftests/mm/uffd-common.c +++ b/tools/testing/selftests/mm/uffd-common.c @@ -262,7 +262,7 @@ static inline void munmap_area(void **area) *area = NULL; }
-static void uffd_test_ctx_clear(void) +void uffd_test_ctx_clear(void) { size_t i;
@@ -298,8 +298,6 @@ int uffd_test_ctx_init(uint64_t features, const char **errmsg) unsigned long nr, cpu; int ret;
- uffd_test_ctx_clear(); - ret = uffd_test_ops->allocate_area((void **)&area_src, true); ret |= uffd_test_ops->allocate_area((void **)&area_dst, false); if (ret) { diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h index 7c4fa964c3b0..870776b5a323 100644 --- a/tools/testing/selftests/mm/uffd-common.h +++ b/tools/testing/selftests/mm/uffd-common.h @@ -105,6 +105,7 @@ extern uffd_test_ops_t *uffd_test_ops;
void uffd_stats_report(struct uffd_args *args, int n_cpus); int uffd_test_ctx_init(uint64_t features, const char **errmsg); +void uffd_test_ctx_clear(void); int userfaultfd_open(uint64_t *features); int uffd_read_msg(int ufd, struct uffd_msg *msg); void wp_range(int ufd, __u64 start, __u64 len, bool wp); diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c index 469e0476af26..7e83829bbb33 100644 --- a/tools/testing/selftests/mm/uffd-stress.c +++ b/tools/testing/selftests/mm/uffd-stress.c @@ -323,8 +323,10 @@ static int userfaultfd_stress(void) uffd_stats_reset(args, nr_cpus);
/* bounce pass */ - if (stress(args)) + if (stress(args)) { + uffd_test_ctx_clear(); return 1; + }
/* Clear all the write protections if there is any */ if (test_uffdio_wp) @@ -354,6 +356,7 @@ static int userfaultfd_stress(void)
uffd_stats_report(args, nr_cpus); } + uffd_test_ctx_clear();
return 0; } diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c index 2709a34a39c5..e7d43c198041 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -1319,6 +1319,7 @@ int main(int argc, char *argv[]) continue; } test->uffd_fn(&args); + uffd_test_ctx_clear(); } }
Currently each test can specify unique operations using uffd_test_ops, however these operations are per-memory type and not per-test. Add uffd_test_case_ops which each test case can customize for its own needs regardless of the memory type being used. Pre- and post-allocation operations are added, some of which will be used in the next patch to implement test-specific operations like madvise after memory is allocated but before it is accessed.
Signed-off-by: Suren Baghdasaryan surenb@google.com --- tools/testing/selftests/mm/uffd-common.c | 13 +++++++++++++ tools/testing/selftests/mm/uffd-common.h | 7 +++++++ tools/testing/selftests/mm/uffd-unit-tests.c | 2 ++ 3 files changed, 22 insertions(+)
diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c index 583e5a4cc0fd..fb3bbc77fd00 100644 --- a/tools/testing/selftests/mm/uffd-common.c +++ b/tools/testing/selftests/mm/uffd-common.c @@ -17,6 +17,7 @@ bool map_shared; bool test_uffdio_wp = true; unsigned long long *count_verify; uffd_test_ops_t *uffd_test_ops; +uffd_test_case_ops_t *uffd_test_case_ops;
static int uffd_mem_fd_create(off_t mem_size, bool hugetlb) { @@ -298,6 +299,12 @@ int uffd_test_ctx_init(uint64_t features, const char **errmsg) unsigned long nr, cpu; int ret;
+ if (uffd_test_case_ops && uffd_test_case_ops->pre_alloc) { + ret = uffd_test_case_ops->pre_alloc(errmsg); + if (ret) + return ret; + } + ret = uffd_test_ops->allocate_area((void **)&area_src, true); ret |= uffd_test_ops->allocate_area((void **)&area_dst, false); if (ret) { @@ -306,6 +313,12 @@ int uffd_test_ctx_init(uint64_t features, const char **errmsg) return ret; }
+ if (uffd_test_case_ops && uffd_test_case_ops->post_alloc) { + ret = uffd_test_case_ops->post_alloc(errmsg); + if (ret) + return ret; + } + ret = userfaultfd_open(&features); if (ret) { if (errmsg) diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h index 870776b5a323..774595ee629e 100644 --- a/tools/testing/selftests/mm/uffd-common.h +++ b/tools/testing/selftests/mm/uffd-common.h @@ -90,6 +90,12 @@ struct uffd_test_ops { }; typedef struct uffd_test_ops uffd_test_ops_t;
+struct uffd_test_case_ops { + int (*pre_alloc)(const char **errmsg); + int (*post_alloc)(const char **errmsg); +}; +typedef struct uffd_test_case_ops uffd_test_case_ops_t; + extern unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size; extern char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap; extern int uffd, uffd_flags, finished, *pipefd, test_type; @@ -102,6 +108,7 @@ extern uffd_test_ops_t anon_uffd_test_ops; extern uffd_test_ops_t shmem_uffd_test_ops; extern uffd_test_ops_t hugetlb_uffd_test_ops; extern uffd_test_ops_t *uffd_test_ops; +extern uffd_test_case_ops_t *uffd_test_case_ops;
void uffd_stats_report(struct uffd_args *args, int n_cpus); int uffd_test_ctx_init(uint64_t features, const char **errmsg); diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c index e7d43c198041..debc423bdbf4 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -78,6 +78,7 @@ typedef struct { uffd_test_fn uffd_fn; unsigned int mem_targets; uint64_t uffd_feature_required; + uffd_test_case_ops_t *test_case_ops; } uffd_test_case_t;
static void uffd_test_report(void) @@ -185,6 +186,7 @@ uffd_setup_environment(uffd_test_args_t *args, uffd_test_case_t *test, { map_shared = mem_type->shared; uffd_test_ops = mem_type->mem_ops; + uffd_test_case_ops = test->test_case_ops;
if (mem_type->mem_flag & (MEM_HUGETLB_PRIVATE | MEM_HUGETLB)) page_size = default_huge_page_size();
Add tests for new UFFDIO_MOVE ioctl which uses uffd to move source into destination buffer while checking the contents of both after the move. After the operation the content of the destination buffer should match the original source buffer's content while the source buffer should be zeroed. Separate tests are designed for PMD aligned and unaligned cases because they utilize different code paths in the kernel.
Signed-off-by: Suren Baghdasaryan surenb@google.com --- tools/testing/selftests/mm/uffd-common.c | 24 +++ tools/testing/selftests/mm/uffd-common.h | 1 + tools/testing/selftests/mm/uffd-unit-tests.c | 189 +++++++++++++++++++ 3 files changed, 214 insertions(+)
diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c index fb3bbc77fd00..b0ac0ec2356d 100644 --- a/tools/testing/selftests/mm/uffd-common.c +++ b/tools/testing/selftests/mm/uffd-common.c @@ -631,6 +631,30 @@ int copy_page(int ufd, unsigned long offset, bool wp) return __copy_page(ufd, offset, false, wp); }
+int move_page(int ufd, unsigned long offset, unsigned long len) +{ + struct uffdio_move uffdio_move; + + if (offset + len > nr_pages * page_size) + err("unexpected offset %lu and length %lu\n", offset, len); + uffdio_move.dst = (unsigned long) area_dst + offset; + uffdio_move.src = (unsigned long) area_src + offset; + uffdio_move.len = len; + uffdio_move.mode = UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES; + uffdio_move.move = 0; + if (ioctl(ufd, UFFDIO_MOVE, &uffdio_move)) { + /* real retval in uffdio_move.move */ + if (uffdio_move.move != -EEXIST) + err("UFFDIO_MOVE error: %"PRId64, + (int64_t)uffdio_move.move); + wake_range(ufd, uffdio_move.dst, len); + } else if (uffdio_move.move != len) { + err("UFFDIO_MOVE error: %"PRId64, (int64_t)uffdio_move.move); + } else + return 1; + return 0; +} + int uffd_open_dev(unsigned int flags) { int fd, uffd; diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h index 774595ee629e..cb055282c89c 100644 --- a/tools/testing/selftests/mm/uffd-common.h +++ b/tools/testing/selftests/mm/uffd-common.h @@ -119,6 +119,7 @@ void wp_range(int ufd, __u64 start, __u64 len, bool wp); void uffd_handle_page_fault(struct uffd_msg *msg, struct uffd_args *args); int __copy_page(int ufd, unsigned long offset, bool retry, bool wp); int copy_page(int ufd, unsigned long offset, bool wp); +int move_page(int ufd, unsigned long offset, unsigned long len); void *uffd_poll_thread(void *arg);
int uffd_open_dev(unsigned int flags); diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c index debc423bdbf4..d8091523c2df 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -23,6 +23,9 @@ #define MEM_ALL (MEM_ANON | MEM_SHMEM | MEM_SHMEM_PRIVATE | \ MEM_HUGETLB | MEM_HUGETLB_PRIVATE)
+#define ALIGN_UP(x, align_to) \ + ((__typeof__(x))((((unsigned long)(x)) + ((align_to)-1)) & ~((align_to)-1))) + struct mem_type { const char *name; unsigned int mem_flag; @@ -1064,6 +1067,178 @@ static void uffd_poison_test(uffd_test_args_t *targs) uffd_test_pass(); }
+static void +uffd_move_handle_fault_common(struct uffd_msg *msg, struct uffd_args *args, + unsigned long len) +{ + unsigned long offset; + + if (msg->event != UFFD_EVENT_PAGEFAULT) + err("unexpected msg event %u", msg->event); + + if (msg->arg.pagefault.flags & + (UFFD_PAGEFAULT_FLAG_WP | UFFD_PAGEFAULT_FLAG_MINOR | UFFD_PAGEFAULT_FLAG_WRITE)) + err("unexpected fault type %llu", msg->arg.pagefault.flags); + + offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst; + offset &= ~(len-1); + + if (move_page(uffd, offset, len)) + args->missing_faults++; +} + +static void uffd_move_handle_fault(struct uffd_msg *msg, + struct uffd_args *args) +{ + uffd_move_handle_fault_common(msg, args, page_size); +} + +static void uffd_move_pmd_handle_fault(struct uffd_msg *msg, + struct uffd_args *args) +{ + uffd_move_handle_fault_common(msg, args, read_pmd_pagesize()); +} + +static void +uffd_move_test_common(uffd_test_args_t *targs, unsigned long chunk_size, + void (*handle_fault)(struct uffd_msg *msg, struct uffd_args *args)) +{ + unsigned long nr; + pthread_t uffd_mon; + char c; + unsigned long long count; + struct uffd_args args = { 0 }; + char *orig_area_src, *orig_area_dst; + unsigned long step_size, step_count; + unsigned long src_offs = 0; + unsigned long dst_offs = 0; + + /* Prevent source pages from being mapped more than once */ + if (madvise(area_src, nr_pages * page_size, MADV_DONTFORK)) + err("madvise(MADV_DONTFORK) failure"); + + if (uffd_register(uffd, area_dst, nr_pages * page_size, + true, false, false)) + err("register failure"); + + args.handle_fault = handle_fault; + if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) + err("uffd_poll_thread create"); + + step_size = chunk_size / page_size; + step_count = nr_pages / step_size; + + if (chunk_size > page_size) { + char *aligned_src = ALIGN_UP(area_src, chunk_size); + char *aligned_dst = ALIGN_UP(area_dst, chunk_size); + + if (aligned_src != area_src || aligned_dst != area_dst) { + src_offs = (aligned_src - area_src) / page_size; + dst_offs = (aligned_dst - area_dst) / page_size; + step_count--; + } + orig_area_src = area_src; + orig_area_dst = area_dst; + area_src = aligned_src; + area_dst = aligned_dst; + } + + /* + * Read each of the pages back using the UFFD-registered mapping. We + * expect that the first time we touch a page, it will result in a missing + * fault. uffd_poll_thread will resolve the fault by moving source + * page to destination. + */ + for (nr = 0; nr < step_count * step_size; nr += step_size) { + unsigned long i; + + /* Check area_src content */ + for (i = 0; i < step_size; i++) { + count = *area_count(area_src, nr + i); + if (count != count_verify[src_offs + nr + i]) + err("nr %lu source memory invalid %llu %llu\n", + nr + i, count, count_verify[src_offs + nr + i]); + } + + /* Faulting into area_dst should move the page or the huge page */ + for (i = 0; i < step_size; i++) { + count = *area_count(area_dst, nr + i); + if (count != count_verify[dst_offs + nr + i]) + err("nr %lu memory corruption %llu %llu\n", + nr, count, count_verify[dst_offs + nr + i]); + } + + /* Re-check area_src content which should be empty */ + for (i = 0; i < step_size; i++) { + count = *area_count(area_src, nr + i); + if (count != 0) + err("nr %lu move failed %llu %llu\n", + nr, count, count_verify[src_offs + nr + i]); + } + } + if (step_size > page_size) { + area_src = orig_area_src; + area_dst = orig_area_dst; + } + + if (write(pipefd[1], &c, sizeof(c)) != sizeof(c)) + err("pipe write"); + if (pthread_join(uffd_mon, NULL)) + err("join() failed"); + + if (args.missing_faults != step_count || args.minor_faults != 0) + uffd_test_fail("stats check error"); + else + uffd_test_pass(); +} + +static void uffd_move_test(uffd_test_args_t *targs) +{ + uffd_move_test_common(targs, page_size, uffd_move_handle_fault); +} + +static void uffd_move_pmd_test(uffd_test_args_t *targs) +{ + uffd_move_test_common(targs, read_pmd_pagesize(), + uffd_move_pmd_handle_fault); +} + +static int prevent_hugepages(const char **errmsg) +{ + /* This should be done before source area is populated */ + if (madvise(area_src, nr_pages * page_size, MADV_NOHUGEPAGE)) { + /* Ignore only if CONFIG_TRANSPARENT_HUGEPAGE=n */ + if (errno != EINVAL) { + if (errmsg) + *errmsg = "madvise(MADV_NOHUGEPAGE) failed"; + return -errno; + } + } + return 0; +} + +static int request_hugepages(const char **errmsg) +{ + /* This should be done before source area is populated */ + if (madvise(area_src, nr_pages * page_size, MADV_HUGEPAGE)) { + if (errmsg) { + *errmsg = (errno == EINVAL) ? + "CONFIG_TRANSPARENT_HUGEPAGE is not set" : + "madvise(MADV_HUGEPAGE) failed"; + } + return -errno; + } + return 0; +} + +struct uffd_test_case_ops uffd_move_test_case_ops = { + .post_alloc = prevent_hugepages, +}; + +struct uffd_test_case_ops uffd_move_test_pmd_case_ops = { + .post_alloc = request_hugepages, +}; + /* * Test the returned uffdio_register.ioctls with different register modes. * Note that _UFFDIO_ZEROPAGE is tested separately in the zeropage test. @@ -1141,6 +1316,20 @@ uffd_test_case_t uffd_tests[] = { .mem_targets = MEM_ALL, .uffd_feature_required = 0, }, + { + .name = "move", + .uffd_fn = uffd_move_test, + .mem_targets = MEM_ANON, + .uffd_feature_required = UFFD_FEATURE_MOVE, + .test_case_ops = &uffd_move_test_case_ops, + }, + { + .name = "move-pmd", + .uffd_fn = uffd_move_pmd_test, + .mem_targets = MEM_ANON, + .uffd_feature_required = UFFD_FEATURE_MOVE, + .test_case_ops = &uffd_move_test_pmd_case_ops, + }, { .name = "wp-fork", .uffd_fn = uffd_wp_fork_test,
On Wed, Dec 06, 2023 at 02:36:59AM -0800, Suren Baghdasaryan wrote:
Add tests for new UFFDIO_MOVE ioctl which uses uffd to move source into destination buffer while checking the contents of both after the move. After the operation the content of the destination buffer should match the original source buffer's content while the source buffer should be zeroed. Separate tests are designed for PMD aligned and unaligned cases because they utilize different code paths in the kernel.
Signed-off-by: Suren Baghdasaryan surenb@google.com
tools/testing/selftests/mm/uffd-common.c | 24 +++ tools/testing/selftests/mm/uffd-common.h | 1 + tools/testing/selftests/mm/uffd-unit-tests.c | 189 +++++++++++++++++++ 3 files changed, 214 insertions(+)
This breaks the build in at least some configurations with separate output directories like those used by KernelCI:
make KBUILD_BUILD_USER=KernelCI FORMAT=.xz ARCH=arm64 HOSTCC=gcc CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- CC="ccache aarch64-linux-gnu-gcc" O=/tmp/kci/linux/build -C/tmp/kci/linux -j10 kselftest-gen_tar
(full logs for both arm64 and x86_64 at):
https://storage.kernelci.org/next/master/next-20231208/arm64/defconfig/gcc-1... https://storage.kernelci.org/next/master/next-20231208/x86_64/x86_64_defconf...
or tuxmake:
make --silent --keep-going --jobs=16 O=/home/broonie/.cache/tuxmake/builds/25/build INSTALL_PATH=/home/broonie/.cache/tuxmake/builds/25/build/kselftest_install ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- kselftest-install
The specific failure:
aarch64-linux-gnu-gcc -Wall -I /tmp/kci/linux/tools/testing/selftests/../../.. -isystem /tmp/kci/linux/build/usr/include uffd-stress.c vm_util.c uffd-common.c -lrt -lpthread -lm -o /tmp/kci/linux/build/kselftest/mm/uffd-stress uffd-common.c: In function ‘move_page’: uffd-common.c:636:21: error: storage size of ‘uffdio_move’ isn’t known 636 | struct uffdio_move uffdio_move; | ^~~~~~~~~~~ uffd-common.c:643:21: error: ‘UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES’ undeclared (first use in this function) 643 | uffdio_move.mode = UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES; | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ uffd-common.c:643:21: note: each undeclared identifier is reported only once for each function it appears in uffd-common.c:645:17: error: ‘UFFDIO_MOVE’ undeclared (first use in this function); did you mean ‘UFFDIO_COPY’? 645 | if (ioctl(ufd, UFFDIO_MOVE, &uffdio_move)) { | ^~~~~~~~~~~ | UFFDIO_COPY uffd-common.c:636:21: warning: unused variable ‘uffdio_move’ [-Wunused-variable] 636 | struct uffdio_move uffdio_move; | ^~~~~~~~~~~
On Sun, Dec 10, 2023 at 6:26 AM Mark Brown broonie@kernel.org wrote:
On Wed, Dec 06, 2023 at 02:36:59AM -0800, Suren Baghdasaryan wrote:
Add tests for new UFFDIO_MOVE ioctl which uses uffd to move source into destination buffer while checking the contents of both after the move. After the operation the content of the destination buffer should match the original source buffer's content while the source buffer should be zeroed. Separate tests are designed for PMD aligned and unaligned cases because they utilize different code paths in the kernel.
Signed-off-by: Suren Baghdasaryan surenb@google.com
tools/testing/selftests/mm/uffd-common.c | 24 +++ tools/testing/selftests/mm/uffd-common.h | 1 + tools/testing/selftests/mm/uffd-unit-tests.c | 189 +++++++++++++++++++ 3 files changed, 214 insertions(+)
This breaks the build in at least some configurations with separate output directories like those used by KernelCI:
make KBUILD_BUILD_USER=KernelCI FORMAT=.xz ARCH=arm64 HOSTCC=gcc CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- CC="ccache aarch64-linux-gnu-gcc" O=/tmp/kci/linux/build -C/tmp/kci/linux -j10 kselftest-gen_tar
(full logs for both arm64 and x86_64 at):
https://storage.kernelci.org/next/master/next-20231208/arm64/defconfig/gcc-1... https://storage.kernelci.org/next/master/next-20231208/x86_64/x86_64_defconf...
or tuxmake:
make --silent --keep-going --jobs=16 O=/home/broonie/.cache/tuxmake/builds/25/build INSTALL_PATH=/home/broonie/.cache/tuxmake/builds/25/build/kselftest_install ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- kselftest-install
The specific failure:
aarch64-linux-gnu-gcc -Wall -I /tmp/kci/linux/tools/testing/selftests/../../.. -isystem /tmp/kci/linux/build/usr/include uffd-stress.c vm_util.c uffd-common.c -lrt -lpthread -lm -o /tmp/kci/linux/build/kselftest/mm/uffd-stress uffd-common.c: In function ‘move_page’: uffd-common.c:636:21: error: storage size of ‘uffdio_move’ isn’t known 636 | struct uffdio_move uffdio_move; | ^~~~~~~~~~~ uffd-common.c:643:21: error: ‘UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES’ undeclared (first use in this function) 643 | uffdio_move.mode = UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES; | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ uffd-common.c:643:21: note: each undeclared identifier is reported only once for each function it appears in uffd-common.c:645:17: error: ‘UFFDIO_MOVE’ undeclared (first use in this function); did you mean ‘UFFDIO_COPY’? 645 | if (ioctl(ufd, UFFDIO_MOVE, &uffdio_move)) { | ^~~~~~~~~~~ | UFFDIO_COPY uffd-common.c:636:21: warning: unused variable ‘uffdio_move’ [-Wunused-variable] 636 | struct uffdio_move uffdio_move; | ^~~~~~~~~~~
Thanks for reporting! I'll try that later today. Just to clarify, are you using mm-unstable and if so, has it been rebased since Friday? There was an update to this patchset in mm-unstable which Andrew merged on Friday and the failure does look like something that would happen with the previous version.
On Sun, Dec 10, 2023 at 5:01 PM Suren Baghdasaryan surenb@google.com wrote:
On Sun, Dec 10, 2023 at 6:26 AM Mark Brown broonie@kernel.org wrote:
On Wed, Dec 06, 2023 at 02:36:59AM -0800, Suren Baghdasaryan wrote:
Add tests for new UFFDIO_MOVE ioctl which uses uffd to move source into destination buffer while checking the contents of both after the move. After the operation the content of the destination buffer should match the original source buffer's content while the source buffer should be zeroed. Separate tests are designed for PMD aligned and unaligned cases because they utilize different code paths in the kernel.
Signed-off-by: Suren Baghdasaryan surenb@google.com
tools/testing/selftests/mm/uffd-common.c | 24 +++ tools/testing/selftests/mm/uffd-common.h | 1 + tools/testing/selftests/mm/uffd-unit-tests.c | 189 +++++++++++++++++++ 3 files changed, 214 insertions(+)
This breaks the build in at least some configurations with separate output directories like those used by KernelCI:
make KBUILD_BUILD_USER=KernelCI FORMAT=.xz ARCH=arm64 HOSTCC=gcc CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- CC="ccache aarch64-linux-gnu-gcc" O=/tmp/kci/linux/build -C/tmp/kci/linux -j10 kselftest-gen_tar
(full logs for both arm64 and x86_64 at):
https://storage.kernelci.org/next/master/next-20231208/arm64/defconfig/gcc-1... https://storage.kernelci.org/next/master/next-20231208/x86_64/x86_64_defconf...
or tuxmake:
make --silent --keep-going --jobs=16 O=/home/broonie/.cache/tuxmake/builds/25/build INSTALL_PATH=/home/broonie/.cache/tuxmake/builds/25/build/kselftest_install ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- kselftest-install
The specific failure:
aarch64-linux-gnu-gcc -Wall -I /tmp/kci/linux/tools/testing/selftests/../../.. -isystem /tmp/kci/linux/build/usr/include uffd-stress.c vm_util.c uffd-common.c -lrt -lpthread -lm -o /tmp/kci/linux/build/kselftest/mm/uffd-stress uffd-common.c: In function ‘move_page’: uffd-common.c:636:21: error: storage size of ‘uffdio_move’ isn’t known 636 | struct uffdio_move uffdio_move; | ^~~~~~~~~~~ uffd-common.c:643:21: error: ‘UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES’ undeclared (first use in this function) 643 | uffdio_move.mode = UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES; | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ uffd-common.c:643:21: note: each undeclared identifier is reported only once for each function it appears in uffd-common.c:645:17: error: ‘UFFDIO_MOVE’ undeclared (first use in this function); did you mean ‘UFFDIO_COPY’? 645 | if (ioctl(ufd, UFFDIO_MOVE, &uffdio_move)) { | ^~~~~~~~~~~ | UFFDIO_COPY uffd-common.c:636:21: warning: unused variable ‘uffdio_move’ [-Wunused-variable] 636 | struct uffdio_move uffdio_move; | ^~~~~~~~~~~
Thanks for reporting! I'll try that later today. Just to clarify, are you using mm-unstable and if so, has it been rebased since Friday? There was an update to this patchset in mm-unstable which Andrew merged on Friday and the failure does look like something that would happen with the previous version.
I tried reproducing the issue but so far unsuccessfully. Could you please confirm that on the latest mm-unstable branch it's still reproducible and if so, please provide detailed instructions on how you reproduce it. Thanks, Suren.
On Sun, Dec 10, 2023 at 07:04:19PM -0800, Suren Baghdasaryan wrote:
On Sun, Dec 10, 2023 at 5:01 PM Suren Baghdasaryan surenb@google.com wrote:
Thanks for reporting! I'll try that later today. Just to clarify, are you using mm-unstable and if so, has it been rebased since Friday? There was an update to this patchset in mm-unstable which Andrew merged on Friday and the failure does look like something that would happen with the previous version.
I tried reproducing the issue but so far unsuccessfully. Could you please confirm that on the latest mm-unstable branch it's still reproducible and if so, please provide detailed instructions on how you reproduce it.
This is linux-next. I pasted the commands used to build and sent links to a full build log in the original report.
On 11.12.23 12:15, Mark Brown wrote:
On Sun, Dec 10, 2023 at 07:04:19PM -0800, Suren Baghdasaryan wrote:
On Sun, Dec 10, 2023 at 5:01 PM Suren Baghdasaryan surenb@google.com wrote:
Thanks for reporting! I'll try that later today. Just to clarify, are you using mm-unstable and if so, has it been rebased since Friday? There was an update to this patchset in mm-unstable which Andrew merged on Friday and the failure does look like something that would happen with the previous version.
I tried reproducing the issue but so far unsuccessfully. Could you please confirm that on the latest mm-unstable branch it's still reproducible and if so, please provide detailed instructions on how you reproduce it.
This is linux-next. I pasted the commands used to build and sent links to a full build log in the original report.
Probably also related to "make headers-install":
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
The general problem is that some mm selftests are currently not written in way that allows them to compile with old linux headers. That's why the build fails if "make headers-install" was not executed, but it does not fail if "make headers-install" was once upon a time executed, but the headers are outdated.
On Mon, Dec 11, 2023 at 01:03:27PM +0100, David Hildenbrand wrote:
On 11.12.23 12:15, Mark Brown wrote:
This is linux-next. I pasted the commands used to build and sent links to a full build log in the original report.
Probably also related to "make headers-install":
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
The general problem is that some mm selftests are currently not written in way that allows them to compile with old linux headers. That's why the build fails if "make headers-install" was not executed, but it does not fail if "make headers-install" was once upon a time executed, but the headers are outdated.
Oh, it's obviously the new headers not being installed. The builds where I'm seeing the problem (my own and KernelCI's) are all fresh containers so there shouldn't be any stale headers lying around.
On Mon, Dec 11, 2023 at 4:24 AM Mark Brown broonie@kernel.org wrote:
On Mon, Dec 11, 2023 at 01:03:27PM +0100, David Hildenbrand wrote:
On 11.12.23 12:15, Mark Brown wrote:
This is linux-next. I pasted the commands used to build and sent links to a full build log in the original report.
Probably also related to "make headers-install":
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
The general problem is that some mm selftests are currently not written in way that allows them to compile with old linux headers. That's why the build fails if "make headers-install" was not executed, but it does not fail if "make headers-install" was once upon a time executed, but the headers are outdated.
Oh, it's obviously the new headers not being installed. The builds where I'm seeing the problem (my own and KernelCI's) are all fresh containers so there shouldn't be any stale headers lying around.
Ok, I was updating my headers and that's why I could not reproduce it. David, should the test be modified to handle old linux headers (disable the new tests #ifndef _UFFDIO_MOVE or some other way)?
On Mon, Dec 11, 2023 at 08:15:11AM -0800, Suren Baghdasaryan wrote:
On Mon, Dec 11, 2023 at 4:24 AM Mark Brown broonie@kernel.org wrote:
Oh, it's obviously the new headers not being installed. The builds where I'm seeing the problem (my own and KernelCI's) are all fresh containers so there shouldn't be any stale headers lying around.
Ok, I was updating my headers and that's why I could not reproduce it. David, should the test be modified to handle old linux headers (disable the new tests #ifndef _UFFDIO_MOVE or some other way)?
Are you sure we're not just missing an updated to the list of headers to copy (under include/uapi IIRC)?
On Mon, Dec 11, 2023 at 8:25 AM Mark Brown broonie@kernel.org wrote:
On Mon, Dec 11, 2023 at 08:15:11AM -0800, Suren Baghdasaryan wrote:
On Mon, Dec 11, 2023 at 4:24 AM Mark Brown broonie@kernel.org wrote:
Oh, it's obviously the new headers not being installed. The builds where I'm seeing the problem (my own and KernelCI's) are all fresh containers so there shouldn't be any stale headers lying around.
Ok, I was updating my headers and that's why I could not reproduce it. David, should the test be modified to handle old linux headers (disable the new tests #ifndef _UFFDIO_MOVE or some other way)?
Are you sure we're not just missing an updated to the list of headers to copy (under include/uapi IIRC)?
Let me double check.
Just to rule out this possibility, linux-next was broken on Friday (see https://lore.kernel.org/all/CAJuCfpFiEqRO4qkFZbUCmGZy-n_ucqgR5NeyvnwXqYh+RU4...). I just checked and it's fixed now. Could you confirm that with the latest linux-next you still see the issue?
On Mon, Dec 11, 2023 at 08:29:06AM -0800, Suren Baghdasaryan wrote:
Just to rule out this possibility, linux-next was broken on Friday (see https://lore.kernel.org/all/CAJuCfpFiEqRO4qkFZbUCmGZy-n_ucqgR5NeyvnwXqYh+RU4...). I just checked and it's fixed now. Could you confirm that with the latest linux-next you still see the issue?
Yes, it looks like it's fixed today - thanks! (The fix was getting masked by the ongoing KVM breakage.)
On Mon, Dec 11, 2023 at 8:34 AM Mark Brown broonie@kernel.org wrote:
On Mon, Dec 11, 2023 at 08:29:06AM -0800, Suren Baghdasaryan wrote:
Just to rule out this possibility, linux-next was broken on Friday (see https://lore.kernel.org/all/CAJuCfpFiEqRO4qkFZbUCmGZy-n_ucqgR5NeyvnwXqYh+RU4...). I just checked and it's fixed now. Could you confirm that with the latest linux-next you still see the issue?
Yes, it looks like it's fixed today - thanks! (The fix was getting masked by the ongoing KVM breakage.)
Very good. Thanks for confirming!
On 11.12.23 17:15, Suren Baghdasaryan wrote:
On Mon, Dec 11, 2023 at 4:24 AM Mark Brown broonie@kernel.org wrote:
On Mon, Dec 11, 2023 at 01:03:27PM +0100, David Hildenbrand wrote:
On 11.12.23 12:15, Mark Brown wrote:
This is linux-next. I pasted the commands used to build and sent links to a full build log in the original report.
Probably also related to "make headers-install":
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
The general problem is that some mm selftests are currently not written in way that allows them to compile with old linux headers. That's why the build fails if "make headers-install" was not executed, but it does not fail if "make headers-install" was once upon a time executed, but the headers are outdated.
Oh, it's obviously the new headers not being installed. The builds where I'm seeing the problem (my own and KernelCI's) are all fresh containers so there shouldn't be any stale headers lying around.
Ok, I was updating my headers and that's why I could not reproduce it. David, should the test be modified to handle old linux headers (disable the new tests #ifndef _UFFDIO_MOVE or some other way)?
That's an open question: do we want to be able to build selftests against any host headers, and not the in-tree headers that have to be manually installed and dirty the git tree?
One obvious drawbacks is that we'll have to deal with all that using a bunch of #ifdef, and the tests that will be built+run will depend on the host headers.
Especially the letter is relevant I think: Our upstream testing won't be able to build+run tests that rely on new upstream features. But that's what some key benefit of these selftests, and being able to run them automatically on a bunch of different combinations upstream.
Further, the tests are closely related to the given kernel version, they are not some completely separate tests.
Moving the the (MM?) selftests to a separate repository would make the decision easier: just like in QEMU etc, we'd simply pull in a headers update and only build against these archived headers.
So I see the options:
(1) Rely on installing the proper in-tree headers. Build will fail if that is not happening.
(2) Make the tests build with any host headers.
(3) Regularly archive the required headers in the selftest directory like external projects like QEMU do.
(3) avoids dirtying the tree as a "make headers_install" would, but it also means that each test that makes use of new uapi has to update the relevant headers (what people working on QEMU are used to).
On Mon, Dec 11, 2023 at 05:32:16PM +0100, David Hildenbrand wrote:
On 11.12.23 17:15, Suren Baghdasaryan wrote:
Ok, I was updating my headers and that's why I could not reproduce it. David, should the test be modified to handle old linux headers (disable the new tests #ifndef _UFFDIO_MOVE or some other way)?
That's an open question: do we want to be able to build selftests against any host headers, and not the in-tree headers that have to be manually installed and dirty the git tree?
Quite a lot of existing selftests rely on the headers being installed to build...
One obvious drawbacks is that we'll have to deal with all that using a bunch of #ifdef, and the tests that will be built+run will depend on the host headers.
Especially the letter is relevant I think: Our upstream testing won't be able to build+run tests that rely on new upstream features. But that's what some key benefit of these selftests, and being able to run them automatically on a bunch of different combinations upstream.
...for exactly this reason. It causes real pain testing new interfaces.
Further, the tests are closely related to the given kernel version, they are not some completely separate tests.
Note that there's a general desire for the tests to *run* with older kernels and use whatever feature test mechanisms exist to skip tests that won't run. That's often needed anyway for configurable things.
(3) avoids dirtying the tree as a "make headers_install" would, but it also means that each test that makes use of new uapi has to update the relevant headers (what people working on QEMU are used to).
Note that you can do an out of tree build to avoid dirtying things.
Further, the tests are closely related to the given kernel version, they are not some completely separate tests.
Note that there's a general desire for the tests to *run* with older kernels and use whatever feature test mechanisms exist to skip tests that won't run. That's often needed anyway for configurable things.
Agreed.
(3) avoids dirtying the tree as a "make headers_install" would, but it also means that each test that makes use of new uapi has to update the relevant headers (what people working on QEMU are used to).
Note that you can do an out of tree build to avoid dirtying things.
Yes, but apparently the simple "make headers_install" will dirty the kernel.
See (and ideally comment on)
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
On Mon, Dec 11, 2023 at 05:53:59PM +0100, David Hildenbrand wrote:
(3) avoids dirtying the tree as a "make headers_install" would, but it also means that each test that makes use of new uapi has to update the relevant headers (what people working on QEMU are used to).
Note that you can do an out of tree build to avoid dirtying things.
Yes, but apparently the simple "make headers_install" will dirty the kernel.
See (and ideally comment on)
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
I mean, I guess people who don't want to install the headers are just not going to be able to build a bunch of tests? There definitely are a bunch of tests where it's not needed so I can see why people would not like being forced to do the headers step if they're only interested in those tests.
On 11.12.23 18:32, Mark Brown wrote:
On Mon, Dec 11, 2023 at 05:53:59PM +0100, David Hildenbrand wrote:
(3) avoids dirtying the tree as a "make headers_install" would, but it also means that each test that makes use of new uapi has to update the relevant headers (what people working on QEMU are used to).
Note that you can do an out of tree build to avoid dirtying things.
Yes, but apparently the simple "make headers_install" will dirty the kernel.
See (and ideally comment on)
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
I mean, I guess people who don't want to install the headers are just not going to be able to build a bunch of tests? There definitely are a bunch of tests where it's not needed so I can see why people would not like being forced to do the headers step if they're only interested in those tests.
Yes. And before that, people mostly had no clue that headers had to be installed in order to compile successfully.
So maybe a warning to give at least some hint might be reasonable.
On Mon, Dec 11, 2023 at 07:00:32PM +0100, David Hildenbrand wrote:
On 11.12.23 18:32, Mark Brown wrote:
On Mon, Dec 11, 2023 at 05:53:59PM +0100, David Hildenbrand wrote:
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
I mean, I guess people who don't want to install the headers are just not going to be able to build a bunch of tests? There definitely are a bunch of tests where it's not needed so I can see why people would not like being forced to do the headers step if they're only interested in those tests.
Yes. And before that, people mostly had no clue that headers had to be installed in order to compile successfully.
So maybe a warning to give at least some hint might be reasonable.
That sounds sensible, especially if we could arrange to flag when the specific tests being built need it.
On 12/11/23 12:01, Mark Brown wrote:
On Mon, Dec 11, 2023 at 07:00:32PM +0100, David Hildenbrand wrote:
On 11.12.23 18:32, Mark Brown wrote:
On Mon, Dec 11, 2023 at 05:53:59PM +0100, David Hildenbrand wrote:
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
I mean, I guess people who don't want to install the headers are just not going to be able to build a bunch of tests? There definitely are a bunch of tests where it's not needed so I can see why people would not like being forced to do the headers step if they're only interested in those tests.
Yes. And before that, people mostly had no clue that headers had to be installed in order to compile successfully.
So maybe a warning to give at least some hint might be reasonable.
That sounds sensible, especially if we could arrange to flag when the specific tests being built need it.
But the end result is messy: not everything builds in some cases. If instead we went back to the little ifdef snippets, such as this (from v5.1):
hugepage-shm.c:
#ifndef SHM_HUGETLB #define SHM_HUGETLB 04000 #endif
...then with a bit of one-time, manual effort, we could get everything to work at all times. And that seems better, doesn't it?
thanks,
On 11.12.23 21:11, John Hubbard wrote:
On 12/11/23 12:01, Mark Brown wrote:
On Mon, Dec 11, 2023 at 07:00:32PM +0100, David Hildenbrand wrote:
On 11.12.23 18:32, Mark Brown wrote:
On Mon, Dec 11, 2023 at 05:53:59PM +0100, David Hildenbrand wrote:
https://lkml.kernel.org/r/20231209020144.244759-1-jhubbard@nvidia.com
I mean, I guess people who don't want to install the headers are just not going to be able to build a bunch of tests? There definitely are a bunch of tests where it's not needed so I can see why people would not like being forced to do the headers step if they're only interested in those tests.
Yes. And before that, people mostly had no clue that headers had to be installed in order to compile successfully.
So maybe a warning to give at least some hint might be reasonable.
That sounds sensible, especially if we could arrange to flag when the specific tests being built need it.
But the end result is messy: not everything builds in some cases. If instead we went back to the little ifdef snippets, such as this (from v5.1):
hugepage-shm.c:
#ifndef SHM_HUGETLB #define SHM_HUGETLB 04000 #endif...then with a bit of one-time, manual effort, we could get everything to work at all times. And that seems better, doesn't it?
I'm not a fan of fixing up host headers on a case-per-case basis using ifdefs. It makes the tests harder to read, write and maintain.
We do have the proper headers in the tree, just not in an consumable way for the tests.
Ideally, we'd either carry our own "consumable" version in the tree, or are able to convert the headers under the hood and place them in a directory where we won't have to dirty the tree -- and only tests that need these headers (e.g., mm selftests) will perform that conversion and include them.
I usually build my stuff in-tree, so I don't really have a lot of experience with out-of-tree selftest builds and the whole kernel header inclusion (and how we could avoid the "make headers" and place the headers somewhere else).
On Tue, Dec 12, 2023 at 04:27:12PM +0100, David Hildenbrand wrote:
I usually build my stuff in-tree, so I don't really have a lot of experience with out-of-tree selftest builds and the whole kernel header inclusion (and how we could avoid the "make headers" and place the headers somewhere else).
It's generally something along the lines of (from tuxmake):
make --silent --keep-going --jobs=15 O=/build/stage/build-work INSTALL_PATH=/build/stage/build-work/kselftest_install ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- kselftest-install
possibly with a -C in there to find the kernel source (from KernelCI):
make KBUILD_BUILD_USER=KernelCI FORMAT=.xz ARCH=arm64 HOSTCC=gcc CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- CC="ccache aarch64-linux-gnu-gcc" O=/tmp/kci/linux/build -C/tmp/kci/linux -j10 kselftest-gen_tar
On 12/11/23 08:32, David Hildenbrand wrote: ...
That's an open question: do we want to be able to build selftests against any host headers, and not the in-tree headers that have to be manually installed and dirty the git tree?
One obvious drawbacks is that we'll have to deal with all that using a bunch of #ifdef, and the tests that will be built+run will depend on the host headers.
Especially the letter is relevant I think: Our upstream testing won't be able to build+run tests that rely on new upstream features. But that's what some key benefit of these selftests, and being able to run them automatically on a bunch of different combinations upstream.
Further, the tests are closely related to the given kernel version, they are not some completely separate tests.
Moving the the (MM?) selftests to a separate repository would make the decision easier: just like in QEMU etc, we'd simply pull in a headers update and only build against these archived headers.
So I see the options:
(1) Rely on installing the proper in-tree headers. Build will fail if that is not happening.
(2) Make the tests build with any host headers.
(3) Regularly archive the required headers in the selftest directory like external projects like QEMU do.
Or (4) Hack in little ifdef snippets, into the selftests, like we used to do. Peter Zijlstra seems to be asking for this, if I understand his (much) earlier comments about this.
thanks,
On Mon, Dec 11, 2023 at 10:46:23AM -0800, John Hubbard wrote:
Or (4) Hack in little ifdef snippets, into the selftests, like we used to do. Peter Zijlstra seems to be asking for this, if I understand his (much) earlier comments about this.
I can't help but think that if we're having to manually copy bits of the uapi headers (which are already separated out in the source) into another part of the same source tree in order to use them then there's room for improvement somewhere. TBH it also doesn't seem great to add additional variables that depend on the user's build environment, we already have enough build issues. It ought to be mostly tedious rather than hard but it's still a pain, especially given the issues we have getting kselftest fixes merged promptly.
On 12/11/23 12:21, Mark Brown wrote:
On Mon, Dec 11, 2023 at 10:46:23AM -0800, John Hubbard wrote:
Or (4) Hack in little ifdef snippets, into the selftests, like we used to do. Peter Zijlstra seems to be asking for this, if I understand his (much) earlier comments about this.
I can't help but think that if we're having to manually copy bits of the uapi headers (which are already separated out in the source) into another part of the same source tree in order to use them then there's room for improvement somewhere. TBH it also doesn't seem great to add
Yes, it feels that way to me, too.
additional variables that depend on the user's build environment, we already have enough build issues. It ought to be mostly tedious rather than hard but it's still a pain, especially given the issues we have getting kselftest fixes merged promptly.
What about David's option (3):
(3) Regularly archive the required headers in the selftest directory like external projects like QEMU do.
, combined with something in the build system to connect it up for building the selftests?
Or maybe there is an innovative way to do all of this, that we have yet to think of.
thanks,
On Mon, Dec 11, 2023 at 12:29:58PM -0800, John Hubbard wrote:
On 12/11/23 12:21, Mark Brown wrote:
additional variables that depend on the user's build environment, we already have enough build issues. It ought to be mostly tedious rather than hard but it's still a pain, especially given the issues we have getting kselftest fixes merged promptly.
What about David's option (3):
(3) Regularly archive the required headers in the selftest directory like external projects like QEMU do.
, combined with something in the build system to connect it up for building the selftests?
Or maybe there is an innovative way to do all of this, that we have yet to think of.
We do copy files into tools/include at random times which makes sense for things that aren't uapi, and we are putting bits of uapi there already so we could just expand the set of files copied there. AFAICT the only reason we're copying the uapi files at all is that they're directly in the same include/ directories as everything else and are always referenced with their uapi/ prefix.
On 12/12/23 07:12, Mark Brown wrote:
On Mon, Dec 11, 2023 at 12:29:58PM -0800, John Hubbard wrote:
On 12/11/23 12:21, Mark Brown wrote:
...
Or maybe there is an innovative way to do all of this, that we have yet to think of.
We do copy files into tools/include at random times which makes sense for things that aren't uapi, and we are putting bits of uapi there already so we could just expand the set of files copied there. AFAICT the only reason we're copying the uapi files at all is that they're directly in the same include/ directories as everything else and are always referenced with their uapi/ prefix.
Oh, this sounds like it would work nicely. No more "make headers" required (hooray!). Instead, the new approach would be "selftests are allowed to include from tools/include", and then we can just start copying the files that we need to that location, and gradually fix up all the selftests.
I really like this, at first reading anyway.
Muhammad, Shuah, others, what do you think?
+Cc: Muhammad Usama Anjum usama.anjum@collabora.com
thanks,
On 12/13/23 7:14 AM, John Hubbard wrote:
On 12/12/23 07:12, Mark Brown wrote:
On Mon, Dec 11, 2023 at 12:29:58PM -0800, John Hubbard wrote:
On 12/11/23 12:21, Mark Brown wrote:
...
Or maybe there is an innovative way to do all of this, that we have yet to think of.
We do copy files into tools/include at random times which makes sense for things that aren't uapi, and we are putting bits of uapi there already so we could just expand the set of files copied there. AFAICT the only reason we're copying the uapi files at all is that they're directly in the same include/ directories as everything else and are always referenced with their uapi/ prefix.
Oh, this sounds like it would work nicely. No more "make headers" required (hooray!). Instead, the new approach would be "selftests are allowed to include from tools/include", and then we can just start copying the files that we need to that location, and gradually fix up all the selftests.
No, this wouldn't work. * The selftests are applications which include default header files. The application don't care from where the header files are picked up at compile time. We should be able to build the application on normal system with latest headers installed without any changes. * The header files cannot be included directly as they need to be processed first which is done by `make headers`. Here is a diff between kernel fs.h and processed header file to be used by applications:
--- include/uapi/linux/fs.h 2023-12-12 14:45:22.857409660 +0500 +++ usr/include/linux/fs.h 2023-12-12 14:49:23.469733573 +0500 @@ -1,6 +1,6 @@ /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ -#ifndef _UAPI_LINUX_FS_H -#define _UAPI_LINUX_FS_H +#ifndef _LINUX_FS_H +#define _LINUX_FS_H
/* * This file has definitions for some important file table structures @@ -13,14 +13,10 @@ #include <linux/limits.h> #include <linux/ioctl.h> #include <linux/types.h> -#ifndef __KERNEL__ #include <linux/fscrypt.h> -#endif
/* Use of MS_* flags within the kernel is restricted to core mount(2) code. */ -#if !defined(__KERNEL__) #include <linux/mount.h> -#endif
/* * It's silly to have NR_OPEN bigger than NR_FILE, but you can change @@ -287,19 +283,19 @@ typedef int __bitwise __kernel_rwf_t;
/* high priority request, poll if possible */ -#define RWF_HIPRI ((__force __kernel_rwf_t)0x00000001) +#define RWF_HIPRI ((__kernel_rwf_t)0x00000001)
/* per-IO O_DSYNC */ -#define RWF_DSYNC ((__force __kernel_rwf_t)0x00000002) +#define RWF_DSYNC ((__kernel_rwf_t)0x00000002)
/* per-IO O_SYNC */ -#define RWF_SYNC ((__force __kernel_rwf_t)0x00000004) +#define RWF_SYNC ((__kernel_rwf_t)0x00000004)
/* per-IO, return -EAGAIN if operation would block */ -#define RWF_NOWAIT ((__force __kernel_rwf_t)0x00000008) +#define RWF_NOWAIT ((__kernel_rwf_t)0x00000008)
/* per-IO O_APPEND */ -#define RWF_APPEND ((__force __kernel_rwf_t)0x00000010) +#define RWF_APPEND ((__kernel_rwf_t)0x00000010)
/* mask of flags supported by the kernel */ #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ @@ -364,4 +360,4 @@ __u64 return_mask; };
-#endif /* _UAPI_LINUX_FS_H */ +#endif /* _LINUX_FS_H */
I really like this, at first reading anyway.
Muhammad, Shuah, others, what do you think?
+Cc: Muhammad Usama Anjum usama.anjum@collabora.com
thanks,
On 12/12/23 19:58, Muhammad Usama Anjum wrote:
... Oh, this sounds like it would work nicely. No more "make headers" required (hooray!). Instead, the new approach would be "selftests are allowed to include from tools/include", and then we can just start copying the files that we need to that location, and gradually fix up all the selftests.
No, this wouldn't work.
- The selftests are applications which include default header files. The
application don't care from where the header files are picked up at compile time. We should be able to build the application on normal system with latest headers installed without any changes.
- The header files cannot be included directly as they need to be processed
first which is done by `make headers`. Here is a diff between kernel fs.h and processed header file to be used by applications:
Well, that's not the proposal. The idea is to snapshot various uapi/ headers into tools/include, just like what is already being done:
$ diff ./include/uapi/linux/fs.h ./tools/include/uapi/linux/fs.h $
thanks,
On 12/12/23 21:52, John Hubbard wrote:
On 12/12/23 19:58, Muhammad Usama Anjum wrote:
... Oh, this sounds like it would work nicely. No more "make headers" required (hooray!). Instead, the new approach would be "selftests are allowed to include from tools/include", and then we can just start copying the files that we need to that location, and gradually fix up all the selftests.
No, this wouldn't work.
- The selftests are applications which include default header files. The
application don't care from where the header files are picked up at compile time. We should be able to build the application on normal system with latest headers installed without any changes.
- The header files cannot be included directly as they need to be
processed first which is done by `make headers`. Here is a diff between kernel fs.h and processed header file to be used by applications:
Well, that's not the proposal. The idea is to snapshot various uapi/ headers into tools/include, just like what is already being done:
$ diff ./include/uapi/linux/fs.h ./tools/include/uapi/linux/fs.h $
Oh sorry, that's exactly what you were saying you don't want. ahem. :)
Another variation though, would be to run "make headers", and snapshot some of those files into tools/include.
thanks,
On 13.12.23 06:55, John Hubbard wrote:
On 12/12/23 21:52, John Hubbard wrote:
On 12/12/23 19:58, Muhammad Usama Anjum wrote:
... Oh, this sounds like it would work nicely. No more "make headers" required (hooray!). Instead, the new approach would be "selftests are allowed to include from tools/include", and then we can just start copying the files that we need to that location, and gradually fix up all the selftests.
No, this wouldn't work.
- The selftests are applications which include default header files. The
application don't care from where the header files are picked up at compile time. We should be able to build the application on normal system with latest headers installed without any changes.
- The header files cannot be included directly as they need to be
processed first which is done by `make headers`. Here is a diff between kernel fs.h and processed header file to be used by applications:
Well, that's not the proposal. The idea is to snapshot various uapi/ headers into tools/include, just like what is already being done:
$ diff ./include/uapi/linux/fs.h ./tools/include/uapi/linux/fs.h $
Oh sorry, that's exactly what you were saying you don't want. ahem. :)
Another variation though, would be to run "make headers", and snapshot some of those files into tools/include.
^ this is what I had in mind
If you're writing a test that needs some new fancy thing, update the relevant header.
On 12/13/23 01:59, David Hildenbrand wrote: ...
Another variation though, would be to run "make headers", and snapshot some of those files into tools/include.
^ this is what I had in mind
If you're writing a test that needs some new fancy thing, update the relevant header.
OK, and Mark Brown's nearby response [1] supports that, as well.
Thus fortified, I plan on doing the following steps:
Step 1: Do nothing about the revert patch that I sent earlier, thus allowing it to continue in its journey (so far, Andrew has moved it into mm-hotfixes-stable branch).
Step 2: Send out a patch for a modest part of selftests/mm, that uses this latest approach, and see how it fares in reviews.
[1] https://lore.kernel.org/c0aa00a2-38a5-42da-9951-64131d936f7e@sirena.org.uk
thanks,
On 13.12.23 23:01, John Hubbard wrote:
On 12/13/23 01:59, David Hildenbrand wrote: ...
Another variation though, would be to run "make headers", and snapshot some of those files into tools/include.
^ this is what I had in mind
If you're writing a test that needs some new fancy thing, update the relevant header.
OK, and Mark Brown's nearby response [1] supports that, as well.
Thus fortified, I plan on doing the following steps:
Step 1: Do nothing about the revert patch that I sent earlier, thus allowing it to continue in its journey (so far, Andrew has moved it into mm-hotfixes-stable branch).
Step 2: Send out a patch for a modest part of selftests/mm, that uses this latest approach, and see how it fares in reviews.
All sounds good to me!
On Wed, Dec 13, 2023 at 08:58:06AM +0500, Muhammad Usama Anjum wrote:
On 12/13/23 7:14 AM, John Hubbard wrote:
Oh, this sounds like it would work nicely. No more "make headers" required (hooray!). Instead, the new approach would be "selftests are allowed to include from tools/include", and then we can just start copying the files that we need to that location, and gradually fix up all the selftests.
No, this wouldn't work.
Note that we have a bunch of selftests (at least arm64, hid, kvm, rseq and sgx from a quick grep) which already use and rely on the headers in tools/include.
- The selftests are applications which include default header files. The
application don't care from where the header files are picked up at compile time. We should be able to build the application on normal system with latest headers installed without any changes.
I think there is much less interest in building out of the kernel than there is in avoiding having to handle random userspace headers...
- The header files cannot be included directly as they need to be processed
first which is done by `make headers`. Here is a diff between kernel fs.h and processed header file to be used by applications:
I guess that's another reason why the sync is done manually. There are also a bunch of files in tools/include that are just completely different implementations of things (not just uapi).
linux-kselftest-mirror@lists.linaro.org
-
Alejandro Colomar -
David Hildenbrand -
John Hubbard -
Lorenzo Stoakes -
Mark Brown -
Muhammad Usama Anjum -
Suren Baghdasaryan