6.6-stable review patch. If anyone has any objections, please let me know.
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From: Harry Yoo harry.yoo@oracle.com
commit 6659d027998083fbb6d42a165b0c90dc2e8ba989 upstream.
Define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() to ensure page tables are properly synchronized when calling p*d_populate_kernel().
For 5-level paging, synchronization is performed via pgd_populate_kernel(). In 4-level paging, pgd_populate() is a no-op, so synchronization is instead performed at the P4D level via p4d_populate_kernel().
This fixes intermittent boot failures on systems using 4-level paging and a large amount of persistent memory:
BUG: unable to handle page fault for address: ffffe70000000034 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI RIP: 0010:__init_single_page+0x9/0x6d Call Trace: <TASK> __init_zone_device_page+0x17/0x5d memmap_init_zone_device+0x154/0x1bb pagemap_range+0x2e0/0x40f memremap_pages+0x10b/0x2f0 devm_memremap_pages+0x1e/0x60 dev_dax_probe+0xce/0x2ec [device_dax] dax_bus_probe+0x6d/0xc9 [... snip ...] </TASK>
It also fixes a crash in vmemmap_set_pmd() caused by accessing vmemmap before sync_global_pgds() [1]:
BUG: unable to handle page fault for address: ffffeb3ff1200000 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: Oops: 0002 [#1] PREEMPT SMP NOPTI Tainted: [W]=WARN RIP: 0010:vmemmap_set_pmd+0xff/0x230 <TASK> vmemmap_populate_hugepages+0x176/0x180 vmemmap_populate+0x34/0x80 __populate_section_memmap+0x41/0x90 sparse_add_section+0x121/0x3e0 __add_pages+0xba/0x150 add_pages+0x1d/0x70 memremap_pages+0x3dc/0x810 devm_memremap_pages+0x1c/0x60 xe_devm_add+0x8b/0x100 [xe] xe_tile_init_noalloc+0x6a/0x70 [xe] xe_device_probe+0x48c/0x740 [xe] [... snip ...]
Link: https://lkml.kernel.org/r/20250818020206.4517-4-harry.yoo@oracle.com Fixes: 8d400913c231 ("x86/vmemmap: handle unpopulated sub-pmd ranges") Signed-off-by: Harry Yoo harry.yoo@oracle.com Closes: https://lore.kernel.org/linux-mm/20250311114420.240341-1-gwan-gyeong.mun@int... [1] Suggested-by: Dave Hansen dave.hansen@linux.intel.com Acked-by: Kiryl Shutsemau kas@kernel.org Reviewed-by: Mike Rapoport (Microsoft) rppt@kernel.org Reviewed-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com Acked-by: David Hildenbrand david@redhat.com Cc: Alexander Potapenko glider@google.com Cc: Alistair Popple apopple@nvidia.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Andy Lutomirski luto@kernel.org Cc: "Aneesh Kumar K.V" aneesh.kumar@linux.ibm.com Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Ard Biesheuvel ardb@kernel.org Cc: Arnd Bergmann arnd@arndb.de Cc: bibo mao maobibo@loongson.cn Cc: Borislav Betkov bp@alien8.de Cc: Christoph Lameter (Ampere) cl@gentwo.org Cc: Dennis Zhou dennis@kernel.org Cc: Dev Jain dev.jain@arm.com Cc: Dmitriy Vyukov dvyukov@google.com Cc: Ingo Molnar mingo@redhat.com Cc: Jane Chu jane.chu@oracle.com Cc: Joao Martins joao.m.martins@oracle.com Cc: Joerg Roedel joro@8bytes.org Cc: John Hubbard jhubbard@nvidia.com Cc: Kevin Brodsky kevin.brodsky@arm.com Cc: Liam Howlett liam.howlett@oracle.com Cc: Michal Hocko mhocko@suse.com Cc: Oscar Salvador osalvador@suse.de Cc: Peter Xu peterx@redhat.com Cc: Peter Zijlstra peterz@infradead.org Cc: Qi Zheng zhengqi.arch@bytedance.com Cc: Ryan Roberts ryan.roberts@arm.com Cc: Suren Baghdasaryan surenb@google.com Cc: Tejun Heo tj@kernel.org Cc: Thomas Gleinxer tglx@linutronix.de Cc: Thomas Huth thuth@redhat.com Cc: "Uladzislau Rezki (Sony)" urezki@gmail.com Cc: Vincenzo Frascino vincenzo.frascino@arm.com Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/pgtable_64_types.h | 3 +++ arch/x86/mm/init_64.c | 18 ++++++++++++++++++ 2 files changed, 21 insertions(+)
--- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -41,6 +41,9 @@ static inline bool pgtable_l5_enabled(vo #define pgtable_l5_enabled() 0 #endif /* CONFIG_X86_5LEVEL */
+#define ARCH_PAGE_TABLE_SYNC_MASK \ + (pgtable_l5_enabled() ? PGTBL_PGD_MODIFIED : PGTBL_P4D_MODIFIED) + extern unsigned int pgdir_shift; extern unsigned int ptrs_per_p4d;
--- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -224,6 +224,24 @@ static void sync_global_pgds(unsigned lo }
/* + * Make kernel mappings visible in all page tables in the system. + * This is necessary except when the init task populates kernel mappings + * during the boot process. In that case, all processes originating from + * the init task copies the kernel mappings, so there is no issue. + * Otherwise, missing synchronization could lead to kernel crashes due + * to missing page table entries for certain kernel mappings. + * + * Synchronization is performed at the top level, which is the PGD in + * 5-level paging systems. But in 4-level paging systems, however, + * pgd_populate() is a no-op, so synchronization is done at the P4D level. + * sync_global_pgds() handles this difference between paging levels. + */ +void arch_sync_kernel_mappings(unsigned long start, unsigned long end) +{ + sync_global_pgds(start, end); +} + +/* * NOTE: This function is marked __ref because it calls __init function * (alloc_bootmem_pages). It's safe to do it ONLY when after_bootmem == 0. */