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[PATCH v23 0/8] fork: Support shadow stacks in clone3()

by Mark Brown

At this point I think everyone in the on the kernel side is happy with this but there were some questions from the glibc side about the value of controlling the shadow stack placement and size, especially with the current inability to reuse the shadow stack for an exited thread. With support for reuse it would be possible to have a cache of shadow stacks as is currently supported for the normal stack. Since the discussion petered out I'm resending this in order to give people something work with while prototyping. It should be possible to prototype any potential kernel features to help build out shadow stack support in userspace by enabling shadow stack writes, as suggested by Rick Edgecombe this may end up being required anyway for supporting more exotic scenarios. On all current architectures with the feature writes to shadow stack require specific instructions so there are still security benefits even with writes enabled. I did send a change implementing a feature writing a token on thread exit to allow reuse: https://lore.kernel.org/r/20250921-arm64-gcs-exit-token-v1-0-45cf64e648d5@k… but wasn't planning to refresh it without some indication from the userspace side that that'd be useful. Non-process cover letter: The kernel has added support for shadow stacks, currently x86 only using their CET feature but both arm64 and RISC-V have equivalent features (GCS and Zicfiss respectively), I am actively working on GCS[1]. With shadow stacks the hardware maintains an additional stack containing only the return addresses for branch instructions which is not generally writeable by userspace and ensures that any returns are to the recorded addresses. This provides some protection against ROP attacks and making it easier to collect call stacks. These shadow stacks are allocated in the address space of the userspace process. Our API for shadow stacks does not currently offer userspace any flexiblity for managing the allocation of shadow stacks for newly created threads, instead the kernel allocates a new shadow stack with the same size as the normal stack whenever a thread is created with the feature enabled. The stacks allocated in this way are freed by the kernel when the thread exits or shadow stacks are disabled for the thread. This lack of flexibility and control isn't ideal, in the vast majority of cases the shadow stack will be over allocated and the implicit allocation and deallocation is not consistent with other interfaces. As far as I can tell the interface is done in this manner mainly because the shadow stack patches were in development since before clone3() was implemented. Since clone3() is readily extensible let's add support for specifying a shadow stack when creating a new thread or process, keeping the current implicit allocation behaviour if one is not specified either with clone3() or through the use of clone(). The user must provide a shadow stack pointer, this must point to memory mapped for use as a shadow stackby map_shadow_stack() with an architecture specified shadow stack token at the top of the stack. Yuri Khrustalev has raised questions from the libc side regarding discoverability of extended clone3() structure sizes[2], this seems like a general issue with clone3(). There was a suggestion to add a hwcap on arm64 which isn't ideal but is doable there, though architecture specific mechanisms would also be needed for x86 (and RISC-V if it's support gets merged before this does). The idea has, however, had strong pushback from the architecture maintainers and it is possible to detect support for this in clone3() by attempting a call with a misaligned shadow stack pointer specified so no hwcap has been added. [1] https://lore.kernel.org/linux-arm-kernel/20241001-arm64-gcs-v13-0-222b78d87… [2] https://lore.kernel.org/r/aCs65ccRQtJBnZ_5@arm.com Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v23: - Rebase onto v6.19-rc1. - Link to v22: https://lore.kernel.org/r/20251015-clone3-shadow-stack-v22-0-a8c8da011427@k… Changes in v22: - Rebase onto v6.18-rc1. - Cover letter updates. - Link to v21: https://lore.kernel.org/r/20250916-clone3-shadow-stack-v21-0-910493527013@k… Changes in v21: - Rebase onto https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git kernel-6.18.clone3 - Rename shadow_stack_token to shstk_token, since it's a simple rename I've kept the acks and reviews but I dropped the tested-bys just to be safe. - Link to v20: https://lore.kernel.org/r/20250902-clone3-shadow-stack-v20-0-4d9fff1c53e7@k… Changes in v20: - Comment fixes and clarifications in x86 arch_shstk_validate_clone() from Rick Edgecombe. - Spelling fix in documentation. - Link to v19: https://lore.kernel.org/r/20250819-clone3-shadow-stack-v19-0-bc957075479b@k… Changes in v19: - Rebase onto v6.17-rc1. - Link to v18: https://lore.kernel.org/r/20250702-clone3-shadow-stack-v18-0-7965d2b694db@k… Changes in v18: - Rebase onto v6.16-rc3. - Thanks to pointers from Yuri Khrustalev this version has been tested on x86 so I have removed the RFT tag. - Clarify clone3_shadow_stack_valid() comment about the Kconfig check. - Remove redundant GCSB DSYNCs in arm64 code. - Fix token validation on x86. - Link to v17: https://lore.kernel.org/r/20250609-clone3-shadow-stack-v17-0-8840ed97ff6f@k… Changes in v17: - Rebase onto v6.16-rc1. - Link to v16: https://lore.kernel.org/r/20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@k… Changes in v16: - Rebase onto v6.15-rc2. - Roll in fixes from x86 testing from Rick Edgecombe. - Rework so that the argument is shadow_stack_token. - Link to v15: https://lore.kernel.org/r/20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@k… Changes in v15: - Rebase onto v6.15-rc1. - Link to v14: https://lore.kernel.org/r/20250206-clone3-shadow-stack-v14-0-805b53af73b9@k… Changes in v14: - Rebase onto v6.14-rc1. - Link to v13: https://lore.kernel.org/r/20241203-clone3-shadow-stack-v13-0-93b89a81a5ed@k… Changes in v13: - Rebase onto v6.13-rc1. - Link to v12: https://lore.kernel.org/r/20241031-clone3-shadow-stack-v12-0-7183eb8bee17@k… Changes in v12: - Add the regular prctl() to the userspace API document since arm64 support is queued in -next. - Link to v11: https://lore.kernel.org/r/20241005-clone3-shadow-stack-v11-0-2a6a2bd6d651@k… Changes in v11: - Rebase onto arm64 for-next/gcs, which is based on v6.12-rc1, and integrate arm64 support. - Rework the interface to specify a shadow stack pointer rather than a base and size like we do for the regular stack. - Link to v10: https://lore.kernel.org/r/20240821-clone3-shadow-stack-v10-0-06e8797b9445@k… Changes in v10: - Integrate fixes & improvements for the x86 implementation from Rick Edgecombe. - Require that the shadow stack be VM_WRITE. - Require that the shadow stack base and size be sizeof(void *) aligned. - Clean up trailing newline. - Link to v9: https://lore.kernel.org/r/20240819-clone3-shadow-stack-v9-0-962d74f99464@ke… Changes in v9: - Pull token validation earlier and report problems with an error return to parent rather than signal delivery to the child. - Verify that the top of the supplied shadow stack is VM_SHADOW_STACK. - Rework token validation to only do the page mapping once. - Drop no longer needed support for testing for signals in selftest. - Fix typo in comments. - Link to v8: https://lore.kernel.org/r/20240808-clone3-shadow-stack-v8-0-0acf37caf14c@ke… Changes in v8: - Fix token verification with user specified shadow stack. - Don't track user managed shadow stacks for child processes. - Link to v7: https://lore.kernel.org/r/20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@ke… Changes in v7: - Rebase onto v6.11-rc1. - Typo fixes. - Link to v6: https://lore.kernel.org/r/20240623-clone3-shadow-stack-v6-0-9ee7783b1fb9@ke… Changes in v6: - Rebase onto v6.10-rc3. - Ensure we don't try to free the parent shadow stack in error paths of x86 arch code. - Spelling fixes in userspace API document. - Additional cleanups and improvements to the clone3() tests to support the shadow stack tests. - Link to v5: https://lore.kernel.org/r/20240203-clone3-shadow-stack-v5-0-322c69598e4b@ke… Changes in v5: - Rebase onto v6.8-rc2. - Rework ABI to have the user allocate the shadow stack memory with map_shadow_stack() and a token. - Force inlining of the x86 shadow stack enablement. - Move shadow stack enablement out into a shared header for reuse by other tests. - Link to v4: https://lore.kernel.org/r/20231128-clone3-shadow-stack-v4-0-8b28ffe4f676@ke… Changes in v4: - Formatting changes. - Use a define for minimum shadow stack size and move some basic validation to fork.c. - Link to v3: https://lore.kernel.org/r/20231120-clone3-shadow-stack-v3-0-a7b8ed3e2acc@ke… Changes in v3: - Rebase onto v6.7-rc2. - Remove stale shadow_stack in internal kargs. - If a shadow stack is specified unconditionally use it regardless of CLONE_ parameters. - Force enable shadow stacks in the selftest. - Update changelogs for RISC-V feature rename. - Link to v2: https://lore.kernel.org/r/20231114-clone3-shadow-stack-v2-0-b613f8681155@ke… Changes in v2: - Rebase onto v6.7-rc1. - Remove ability to provide preallocated shadow stack, just specify the desired size. - Link to v1: https://lore.kernel.org/r/20231023-clone3-shadow-stack-v1-0-d867d0b5d4d0@ke… --- Mark Brown (8): arm64/gcs: Return a success value from gcs_alloc_thread_stack() Documentation: userspace-api: Add shadow stack API documentation selftests: Provide helper header for shadow stack testing fork: Add shadow stack support to clone3() selftests/clone3: Remove redundant flushes of output streams selftests/clone3: Factor more of main loop into test_clone3() selftests/clone3: Allow tests to flag if -E2BIG is a valid error code selftests/clone3: Test shadow stack support Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/shadow_stack.rst | 44 +++++ arch/arm64/include/asm/gcs.h | 8 +- arch/arm64/kernel/process.c | 8 +- arch/arm64/mm/gcs.c | 55 +++++- arch/x86/include/asm/shstk.h | 11 +- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/shstk.c | 53 ++++- include/asm-generic/cacheflush.h | 11 ++ include/linux/sched/task.h | 17 ++ include/uapi/linux/sched.h | 9 +- kernel/fork.c | 93 +++++++-- tools/testing/selftests/clone3/clone3.c | 226 ++++++++++++++++++---- tools/testing/selftests/clone3/clone3_selftests.h | 65 ++++++- tools/testing/selftests/ksft_shstk.h | 98 ++++++++++ 15 files changed, 620 insertions(+), 81 deletions(-) --- base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8 change-id: 20231019-clone3-shadow-stack-15d40d2bf536 Best regards, -- Mark Brown <broonie(a)kernel.org>

1 day, 13 hours

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[PATCH v2] selftests/filesystems: Assume that TIOCGPTPEER is defined

by Mark Brown

The devpts_pts selftest has an ifdef in case an architecture does not define TIOCGPTPEER, but the handling for this is broken since we need errno to be set to EINVAL in order to skip the test as we should. Given that this ioctl() has been defined since v4.15 we may as well just assume it's there rather than write handling code which will probably never get used. Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v2: - Rebase onto v6.19-rc1. - Link to v1: https://patch.msgid.link/20251126-selftests-filesystems-devpts-tiocgptpeer-… --- tools/testing/selftests/filesystems/devpts_pts.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/tools/testing/selftests/filesystems/devpts_pts.c b/tools/testing/selftests/filesystems/devpts_pts.c index 54fea349204e..950e8b7f675b 100644 --- a/tools/testing/selftests/filesystems/devpts_pts.c +++ b/tools/testing/selftests/filesystems/devpts_pts.c @@ -100,7 +100,7 @@ static int resolve_procfd_symlink(int fd, char *buf, size_t buflen) static int do_tiocgptpeer(char *ptmx, char *expected_procfd_contents) { int ret; - int master = -1, slave = -1, fret = -1; + int master = -1, slave, fret = -1; master = open(ptmx, O_RDWR | O_NOCTTY | O_CLOEXEC); if (master < 0) { @@ -119,9 +119,7 @@ static int do_tiocgptpeer(char *ptmx, char *expected_procfd_contents) goto do_cleanup; } -#ifdef TIOCGPTPEER slave = ioctl(master, TIOCGPTPEER, O_RDWR | O_NOCTTY | O_CLOEXEC); -#endif if (slave < 0) { if (errno == EINVAL) { fprintf(stderr, "TIOCGPTPEER is not supported. " --- base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8 change-id: 20251126-selftests-filesystems-devpts-tiocgptpeer-fbd30e579859 Best regards, -- Mark Brown <broonie(a)kernel.org>

1 day, 16 hours

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[PATCH v2 0/9] KVM: x86: Improve the handling of debug exceptions during instruction emulation

by Hou Wenlong

During my testing, I found that guest debugging with 'DR6.BD' does not work in instruction emulation, as the current code only considers the guest's DR7. Upon reviewing the code, I also observed that the checks for the userspace guest debugging feature and the guest's own debugging feature are repeated in different places during instruction emulation, but the overall logic is the same. If guest debug is enabled, it needs to exit to userspace; otherwise, a #DB exception needs to be injected into the guest. Therefore, as suggested by Jiangshan Lai, some cleanup has been done for #DB handling in instruction emulation in this patchset. A new function named 'kvm_inject_emulated_db()' is introduced to consolidate all the checking logic. Moreover, I hope we can make the #DB interception path use the same function as well. Additionally, when I looked into the single-step #DB handling in instruction emulation, I noticed that the interrupt shadow is toggled, but it is not considered in the single-step #DB injection. This oversight causes VM entry to fail on VMX (due to pending debug exceptions state checking). As pointed out by Sean, fault-like code #DBs can be coincident with trap-like single-step #DBs at the instruction boundary on the hardware. However it is difficult to emulate this in the emulator, as kvm_vcpu_check_code_breakpoint() is called at the start of the next instruction while the single-step #DB for the previous instruction has already been injected. v1->v2: - cleanup in inject_emulated_exception(). - rename 'set_pending_dbg' callback as 'refresh_pending_dbg_exceptions'. - fold refresh_pending_dbg_exceptions() call into kvm_vcpu_do_singlestep(). - Split the change to move up kvm_set_rflags() into a single patch. - Move the #DB and IRQ handler registration after guest debug testcases. Hou Wenlong (9): KVM: x86: Capture "struct x86_exception" in inject_emulated_exception() KVM: x86: Set guest DR6 by kvm_queue_exception_p() in instruction emulation KVM: x86: Check guest debug in DR access instruction emulation KVM: x86: Only check effective code breakpoint in emulation KVM: x86: Consolidate KVM_GUESTDBG_SINGLESTEP check into the kvm_inject_emulated_db() KVM: x86: Move kvm_set_rflags() up before kvm_vcpu_do_singlestep() KVM: VMX: Refresh 'PENDING_DBG_EXCEPTIONS.BS' bit during instruction emulation KVM: selftests: Verify guest debug DR7.GD checking during instruction emulation KVM: selftests: Verify 'BS' bit checking in pending debug exception during VM entry arch/x86/include/asm/kvm-x86-ops.h | 1 + arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/emulate.c | 14 +-- arch/x86/kvm/kvm_emulate.h | 7 +- arch/x86/kvm/vmx/main.c | 9 ++ arch/x86/kvm/vmx/vmx.c | 15 ++- arch/x86/kvm/vmx/x86_ops.h | 1 + arch/x86/kvm/x86.c | 116 ++++++++++-------- arch/x86/kvm/x86.h | 7 ++ .../selftests/kvm/include/x86/processor.h | 3 +- tools/testing/selftests/kvm/x86/debug_regs.c | 72 ++++++++++- 11 files changed, 178 insertions(+), 68 deletions(-) base-commit: 5d3e2d9ba9ed68576c70c127e4f7446d896f2af2 -- 2.31.1

1 day, 18 hours

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[PATCH 0/7] KVM: x86: Improve the handling of debug exceptions during instruction emulation

by Hou Wenlong

During my testing, I found that guest debugging with 'DR6.BD' does not work in instruction emulation, as the current code only considers the guest's DR7. Upon reviewing the code, I also observed that the checks for the userspace guest debugging feature and the guest's own debugging feature are repeated in different places during instruction emulation, but the overall logic is the same. If guest debugging is enabled, it needs to exit to userspace; otherwise, a #DB exception needs to be injected into the guest. Therefore, as suggested by Jiangshan Lai, some cleanup has been done for #DB handling in instruction emulation in this patchset. A new function named 'kvm_inject_emulated_db()' is introduced to consolidate all the checking logic. Moreover, I hope we can make the #DB interception path use the same function as well. Additionally, when I looked into the single-step #DB handling in instruction emulation, I noticed that the interrupt shadow is toggled, but it is not considered in the single-step #DB injection. This oversight causes VM entry to fail on VMX (due to pending debug exceptions checking) or breaks the 'MOV SS' suppressed #DB. For the latter, I have kept the behavior for now in my patchset, as I need some suggestions. Hou Wenlong (7): KVM: x86: Set guest DR6 by kvm_queue_exception_p() in instruction emulation KVM: x86: Check guest debug in DR access instruction emulation KVM: x86: Only check effective code breakpoint in emulation KVM: x86: Consolidate KVM_GUESTDBG_SINGLESTEP check into the kvm_inject_emulated_db() KVM: VMX: Set 'BS' bit in pending debug exceptions during instruction emulation KVM: selftests: Verify guest debug DR7.GD checking during instruction emulation KVM: selftests: Verify 'BS' bit checking in pending debug exception during VM entry arch/x86/include/asm/kvm-x86-ops.h | 1 + arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/emulate.c | 14 +-- arch/x86/kvm/kvm_emulate.h | 7 +- arch/x86/kvm/vmx/main.c | 9 ++ arch/x86/kvm/vmx/vmx.c | 14 ++- arch/x86/kvm/vmx/x86_ops.h | 1 + arch/x86/kvm/x86.c | 109 +++++++++++------- arch/x86/kvm/x86.h | 7 ++ .../selftests/kvm/include/x86/processor.h | 3 +- tools/testing/selftests/kvm/x86/debug_regs.c | 64 +++++++++- 11 files changed, 167 insertions(+), 63 deletions(-) base-commit: ecbcc2461839e848970468b44db32282e5059925 -- 2.31.1

1 day, 18 hours

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[PATCH v3 0/3] selftests/filelock: Make output more kselftestish

by Mark Brown

This series makes the output from the ofdlocks test a bit easier for tooling to work with, and also ignores the generated file while we're here. Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v3: - Rebase onto v6.19-rc1. - Link to v2: https://lore.kernel.org/r/20251015-selftest-filelock-ktap-v2-0-f5fd21b75c3a… Changes in v2: - Rebase onto v6.18-rc1. - Link to v1: https://lore.kernel.org/r/20250818-selftest-filelock-ktap-v1-0-d41af77f1396… --- Mark Brown (3): kselftest/filelock: Use ksft_perror() kselftest/filelock: Report each test in oftlocks separately kselftest/filelock: Add a .gitignore file tools/testing/selftests/filelock/.gitignore | 1 + tools/testing/selftests/filelock/ofdlocks.c | 94 +++++++++++++---------------- 2 files changed, 42 insertions(+), 53 deletions(-) --- base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8 change-id: 20250604-selftest-filelock-ktap-f2ae998a0de0 Best regards, -- Mark Brown <broonie(a)kernel.org>

1 day, 21 hours

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Issue in parsing of tests that use KUNIT_CASE_PARAM

by Ojaswin Mujoo

Hello, While writing some Kunit tests for ext4 filesystem, I'm encountering an issue in the way we display the diagnostic logs upon failures, when using KUNIT_CASE_PARAM() to write the tests. This can be observed by patching fs/ext4/mballoc-test.c to fail and print one of the params: --- a/fs/ext4/mballoc-test.c +++ b/fs/ext4/mballoc-test.c @@ -350,6 +350,8 @@ static int mbt_kunit_init(struct kunit *test) struct super_block *sb; int ret; + KUNIT_FAIL(test, "Failed: blocksize_bits=%d", layout->blocksize_bits); + sb = mbt_ext4_alloc_super_block(); if (sb == NULL) return -ENOMEM; With the above change, we can observe the following output (snipped): [18:50:25] ============== ext4_mballoc_test (7 subtests) ============== [18:50:25] ================= test_new_blocks_simple ================== [18:50:25] [FAILED] block_bits=10 cluster_bits=3 blocks_per_group=8192 group_count=4 desc_size=64 [18:50:25] # test_new_blocks_simple: EXPECTATION FAILED at fs/ext4/mballoc-test.c:364 [18:50:25] Failed: blocksize_bits=12 [18:50:25] [FAILED] block_bits=12 cluster_bits=3 blocks_per_group=8192 group_count=4 desc_size=64 [18:50:25] # test_new_blocks_simple: EXPECTATION FAILED at fs/ext4/mballoc-test.c:364 [18:50:25] Failed: blocksize_bits=16 [18:50:25] [FAILED] block_bits=16 cluster_bits=3 blocks_per_group=8192 group_count=4 desc_size=64 [18:50:25] # test_new_blocks_simple: EXPECTATION FAILED at fs/ext4/mballoc-test.c:364 [18:50:25] Failed: blocksize_bits=10 [18:50:25] # test_new_blocks_simple: pass:0 fail:3 skip:0 total:3 [18:50:25] ============= [FAILED] test_new_blocks_simple ============== <snip> Note that the diagnostic logs don't show up correctly. Ideally they should be before test result but here the first [FAILED] test has no logs printed above whereas the last "Failed: blocksize_bits=10" print comes after the last subtest, when it actually corresponds to the first subtest. The KTAP file itself seems to have diagnostic logs in the right place: KTAP version 1 1..2 KTAP version 1 # Subtest: ext4_mballoc_test # module: ext4 1..7 KTAP version 1 # Subtest: test_new_blocks_simple # test_new_blocks_simple: EXPECTATION FAILED at fs/ext4/mballoc-test.c:364 Failed: blocksize_bits=10 not ok 1 block_bits=10 cluster_bits=3 blocks_per_group=8192 group_count=4 desc_size=64 # test_new_blocks_simple: EXPECTATION FAILED at fs/ext4/mballoc-test.c:364 Failed: blocksize_bits=12 not ok 2 block_bits=12 cluster_bits=3 blocks_per_group=8192 group_count=4 desc_size=64 # test_new_blocks_simple: EXPECTATION FAILED at fs/ext4/mballoc-test.c:364 Failed: blocksize_bits=16 not ok 3 block_bits=16 cluster_bits=3 blocks_per_group=8192 group_count=4 desc_size=64 # test_new_blocks_simple: pass:0 fail:3 skip:0 total:3 not ok 1 test_new_blocks_simple <snip> By tracing kunit_parser.py script, I could see the issue here is in the parsing of the "Subtest: test_new_blocks_simple". We end up associating everything below the subtest till "not ok 1 block_bits=10..." as diagnostic logs of the subtest, while these lons actually belong to the first of the 3 subtests under this test. I tired to figure out a way to fix the parsing but fixing one thing broke something else. Im starting to think that the issue is that there are 3 subtests under test_new_block_simple (array of 3 params passed to KUNIT_CASE_PARAM), but instead of creating 3 structured subtests, the KTAP output dumps the results of all 3 directly under subtest:test_new_blocks_simple. Which makes it tricky to determine where the diagnostic log/attributes of test_new_blocks_simple ends and that of its children begins. I'm not very familiar with KUnit framework so I though I'd reach out here for some pointers. I can dedicate some time fixing this but I'd like to know if this is something we need to somehow fix in parsing or during generation of the KTAP file itself? Any pointers would be appreciated. Thanks, Ojaswin

1 day, 21 hours

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[PATCH][v2] watchdog: softlockup: panic when lockup duration exceeds N thresholds

by lirongqing

From: Li RongQing <lirongqing(a)baidu.com> The softlockup_panic sysctl is currently a binary option: panic immediately or never panic on soft lockups. Panicking on any soft lockup, regardless of duration, can be overly aggressive for brief stalls that may be caused by legitimate operations. Conversely, never panicking may allow severe system hangs to persist undetected. Extend softlockup_panic to accept an integer threshold, allowing the kernel to panic only when the normalized lockup duration exceeds N watchdog threshold periods. This provides finer-grained control to distinguish between transient delays and persistent system failures. The accepted values are: - 0: Don't panic (unchanged) - 1: Panic when duration >= 1 * threshold (20s default, original behavior) - N > 1: Panic when duration >= N * threshold (e.g., 2 = 40s, 3 = 60s.) The original behavior is preserved for values 0 and 1, maintaining full backward compatibility while allowing systems to tolerate brief lockups while still catching severe, persistent hangs. Signed-off-by: Li RongQing <lirongqing(a)baidu.com> Cc: Eduard Zingerman <eddyz87(a)gmail.com> Cc: Hao Luo <haoluo(a)google.com> Cc: Jiri Olsa <jolsa(a)kernel.org> Cc: John Fastabend <john.fastabend(a)gmail.com> Cc: KP Singh <kpsingh(a)kernel.org> Cc: Lance Yang <lance.yang(a)linux.dev> Cc: Martin KaFai Lau <martin.lau(a)linux.dev> Cc: Nicholas Piggin <npiggin(a)gmail.com> Cc: Song Liu <song(a)kernel.org> Cc: Stanislav Fomichev <sdf(a)fomichev.me> Cc: Yonghong Song <yonghong.song(a)linux.dev> Cc: Andrew Morton <akpm(a)linux-foundation.org> --- Diff with v1: add a temp variable thresh_count chang config to 0 in kernel/configs/debug.config Documentation/admin-guide/kernel-parameters.txt | 10 +++++----- arch/arm/configs/aspeed_g5_defconfig | 2 +- arch/arm/configs/pxa3xx_defconfig | 2 +- arch/openrisc/configs/or1klitex_defconfig | 2 +- arch/powerpc/configs/skiroot_defconfig | 2 +- drivers/gpu/drm/ci/arm.config | 2 +- drivers/gpu/drm/ci/arm64.config | 2 +- drivers/gpu/drm/ci/x86_64.config | 2 +- kernel/configs/debug.config | 2 +- kernel/watchdog.c | 10 ++++++---- lib/Kconfig.debug | 13 +++++++------ tools/testing/selftests/bpf/config | 2 +- tools/testing/selftests/wireguard/qemu/kernel.config | 2 +- 13 files changed, 28 insertions(+), 25 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a8d0afd..27c5f96 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6934,12 +6934,12 @@ Kernel parameters softlockup_panic= [KNL] Should the soft-lockup detector generate panics. - Format: 0 | 1 + Format: <int> - A value of 1 instructs the soft-lockup detector - to panic the machine when a soft-lockup occurs. It is - also controlled by the kernel.softlockup_panic sysctl - and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the + A value of non-zero instructs the soft-lockup detector + to panic the machine when a soft-lockup duration exceeds + N thresholds. It is also controlled by the kernel.softlockup_panic + sysctl and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the respective build-time switch to that functionality. softlockup_all_cpu_backtrace= diff --git a/arch/arm/configs/aspeed_g5_defconfig b/arch/arm/configs/aspeed_g5_defconfig index 2e6ea13..ec558e5 100644 --- a/arch/arm/configs/aspeed_g5_defconfig +++ b/arch/arm/configs/aspeed_g5_defconfig @@ -306,7 +306,7 @@ CONFIG_SCHED_STACK_END_CHECK=y CONFIG_PANIC_ON_OOPS=y CONFIG_PANIC_TIMEOUT=-1 CONFIG_SOFTLOCKUP_DETECTOR=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 CONFIG_BOOTPARAM_HUNG_TASK_PANIC=1 CONFIG_WQ_WATCHDOG=y # CONFIG_SCHED_DEBUG is not set diff --git a/arch/arm/configs/pxa3xx_defconfig b/arch/arm/configs/pxa3xx_defconfig index 07d422f..fb272e3 100644 --- a/arch/arm/configs/pxa3xx_defconfig +++ b/arch/arm/configs/pxa3xx_defconfig @@ -100,7 +100,7 @@ CONFIG_PRINTK_TIME=y CONFIG_DEBUG_KERNEL=y CONFIG_MAGIC_SYSRQ=y CONFIG_DEBUG_SHIRQ=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 # CONFIG_SCHED_DEBUG is not set CONFIG_DEBUG_SPINLOCK=y CONFIG_DEBUG_SPINLOCK_SLEEP=y diff --git a/arch/openrisc/configs/or1klitex_defconfig b/arch/openrisc/configs/or1klitex_defconfig index fb1eb9a..984b0e3 100644 --- a/arch/openrisc/configs/or1klitex_defconfig +++ b/arch/openrisc/configs/or1klitex_defconfig @@ -52,5 +52,5 @@ CONFIG_LSM="lockdown,yama,loadpin,safesetid,integrity,bpf" CONFIG_PRINTK_TIME=y CONFIG_PANIC_ON_OOPS=y CONFIG_SOFTLOCKUP_DETECTOR=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 CONFIG_BUG_ON_DATA_CORRUPTION=y diff --git a/arch/powerpc/configs/skiroot_defconfig b/arch/powerpc/configs/skiroot_defconfig index 2b71a6d..a4114fc 100644 --- a/arch/powerpc/configs/skiroot_defconfig +++ b/arch/powerpc/configs/skiroot_defconfig @@ -289,7 +289,7 @@ CONFIG_SCHED_STACK_END_CHECK=y CONFIG_DEBUG_STACKOVERFLOW=y CONFIG_PANIC_ON_OOPS=y CONFIG_SOFTLOCKUP_DETECTOR=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 CONFIG_HARDLOCKUP_DETECTOR=y CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y CONFIG_WQ_WATCHDOG=y diff --git a/drivers/gpu/drm/ci/arm.config b/drivers/gpu/drm/ci/arm.config index 411e814..d7c5167 100644 --- a/drivers/gpu/drm/ci/arm.config +++ b/drivers/gpu/drm/ci/arm.config @@ -52,7 +52,7 @@ CONFIG_TMPFS=y CONFIG_PROVE_LOCKING=n CONFIG_DEBUG_LOCKDEP=n CONFIG_SOFTLOCKUP_DETECTOR=n -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=n +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=0 CONFIG_FW_LOADER_COMPRESS=y diff --git a/drivers/gpu/drm/ci/arm64.config b/drivers/gpu/drm/ci/arm64.config index fddfbd4..ea0e307 100644 --- a/drivers/gpu/drm/ci/arm64.config +++ b/drivers/gpu/drm/ci/arm64.config @@ -161,7 +161,7 @@ CONFIG_TMPFS=y CONFIG_PROVE_LOCKING=n CONFIG_DEBUG_LOCKDEP=n CONFIG_SOFTLOCKUP_DETECTOR=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 CONFIG_DETECT_HUNG_TASK=y diff --git a/drivers/gpu/drm/ci/x86_64.config b/drivers/gpu/drm/ci/x86_64.config index 8eaba388..7ac98a7 100644 --- a/drivers/gpu/drm/ci/x86_64.config +++ b/drivers/gpu/drm/ci/x86_64.config @@ -47,7 +47,7 @@ CONFIG_TMPFS=y CONFIG_PROVE_LOCKING=n CONFIG_DEBUG_LOCKDEP=n CONFIG_SOFTLOCKUP_DETECTOR=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 CONFIG_DETECT_HUNG_TASK=y diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config index 9f6ab7d..774702591 100644 --- a/kernel/configs/debug.config +++ b/kernel/configs/debug.config @@ -84,7 +84,7 @@ CONFIG_SLUB_DEBUG_ON=y # Debug Oops, Lockups and Hangs # CONFIG_BOOTPARAM_HUNG_TASK_PANIC=0 -# CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC is not set +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=0 CONFIG_DEBUG_ATOMIC_SLEEP=y CONFIG_DETECT_HUNG_TASK=y CONFIG_PANIC_ON_OOPS=y diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 0685e3a..8168e0d 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -363,7 +363,7 @@ static struct cpumask watchdog_allowed_mask __read_mostly; /* Global variables, exported for sysctl */ unsigned int __read_mostly softlockup_panic = - IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC); + CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC; static bool softlockup_initialized __read_mostly; static u64 __read_mostly sample_period; @@ -774,8 +774,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) { unsigned long touch_ts, period_ts, now; struct pt_regs *regs = get_irq_regs(); - int duration; int softlockup_all_cpu_backtrace; + int duration, thresh_count; unsigned long flags; if (!watchdog_enabled) @@ -879,7 +879,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); sys_info(softlockup_si_mask & ~SYS_INFO_ALL_BT); - if (softlockup_panic) + thresh_count = duration / get_softlockup_thresh(); + + if (softlockup_panic && thresh_count >= softlockup_panic) panic("softlockup: hung tasks"); } @@ -1228,7 +1230,7 @@ static const struct ctl_table watchdog_sysctls[] = { .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_ONE, + .extra2 = SYSCTL_INT_MAX, }, { .procname = "softlockup_sys_info", diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index ba36939..17a7a77 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1110,13 +1110,14 @@ config SOFTLOCKUP_DETECTOR_INTR_STORM the CPU stats and the interrupt counts during the "soft lockups". config BOOTPARAM_SOFTLOCKUP_PANIC - bool "Panic (Reboot) On Soft Lockups" + int "Panic (Reboot) On Soft Lockups" depends on SOFTLOCKUP_DETECTOR + default 0 help - Say Y here to enable the kernel to panic on "soft lockups", - which are bugs that cause the kernel to loop in kernel - mode for more than 20 seconds (configurable using the watchdog_thresh - sysctl), without giving other tasks a chance to run. + Set to a non-zero value N to enable the kernel to panic on "soft + lockups", which are bugs that cause the kernel to loop in kernel + mode for more than (N * 20 seconds) (configurable using the + watchdog_thresh sysctl), without giving other tasks a chance to run. The panic can be used in combination with panic_timeout, to cause the system to reboot automatically after a @@ -1124,7 +1125,7 @@ config BOOTPARAM_SOFTLOCKUP_PANIC high-availability systems that have uptime guarantees and where a lockup must be resolved ASAP. - Say N if unsure. + Say 0 if unsure. config HAVE_HARDLOCKUP_DETECTOR_BUDDY bool diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config index 558839e..2485538 100644 --- a/tools/testing/selftests/bpf/config +++ b/tools/testing/selftests/bpf/config @@ -1,6 +1,6 @@ CONFIG_BLK_DEV_LOOP=y CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 CONFIG_BPF=y CONFIG_BPF_EVENTS=y CONFIG_BPF_JIT=y diff --git a/tools/testing/selftests/wireguard/qemu/kernel.config b/tools/testing/selftests/wireguard/qemu/kernel.config index 0504c11..bb89d2d 100644 --- a/tools/testing/selftests/wireguard/qemu/kernel.config +++ b/tools/testing/selftests/wireguard/qemu/kernel.config @@ -80,7 +80,7 @@ CONFIG_HARDLOCKUP_DETECTOR=y CONFIG_WQ_WATCHDOG=y CONFIG_DETECT_HUNG_TASK=y CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y -CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y +CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1 CONFIG_BOOTPARAM_HUNG_TASK_PANIC=1 CONFIG_PANIC_TIMEOUT=-1 CONFIG_STACKTRACE=y -- 2.9.4

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[PATCHSET v11 sched_ext/for-6.20] Add a deadline server for sched_ext tasks

by Andrea Righi

sched_ext tasks can be starved by long-running RT tasks, especially since RT throttling was replaced by deadline servers to boost only SCHED_NORMAL tasks. Several users in the community have reported issues with RT stalling sched_ext tasks. This is fairly common on distributions or environments where applications like video compositors, audio services, etc. run as RT tasks by default. Example trace (showing a per-CPU kthread stalled due to the sway Wayland compositor running as an RT task): runnable task stall (kworker/0:0[106377] failed to run for 5.043s) ... CPU 0 : nr_run=3 flags=0xd cpu_rel=0 ops_qseq=20646200 pnt_seq=45388738 curr=sway[994] class=rt_sched_class R kworker/0:0[106377] -5043ms scx_state/flags=3/0x1 dsq_flags=0x0 ops_state/qseq=0/0 sticky/holding_cpu=-1/-1 dsq_id=0x8000000000000002 dsq_vtime=0 slice=20000000 cpus=01 This is often perceived as a bug in the BPF schedulers, but in reality they can't do much: RT tasks run outside their control and can potentially consume 100% of the CPU bandwidth. Fix this by adding a sched_ext deadline server, so that sched_ext tasks are also boosted and do not suffer starvation. Two kselftests are also provided to verify the starvation fixes and bandwidth allocation is correct. == Design == - The EXT server is initialized at boot time and remains configured throughout the system's lifetime - It starts automatically when the first sched_ext task is enqueued (rq->scx.nr_running == 1) - The server's pick function (ext_server_pick_task) always selects sched_ext tasks when active - Runtime accounting happens in update_curr_scx() during task execution and update_curr_idle() when idle - Bandwidth accounting includes both fair and ext servers in root domain calculations - A debugfs interface (/sys/kernel/debug/sched/ext_server/) allows runtime tuning of server parameters == Highlights in this version == As discussed at the sched_ext microconference at LPC Tokyo, the plan is to start with a simpler approach, avoiding automatically creating or tearing down the EXT server bandwidth reservation when a BPF scheduler is loaded or unloaded. Instead, the reservation is kept permanently active. This significantly simplifies the logic while still addressing the starvation issue. Any fine-tuning of the bandwidth reservation is delegated to the system administrator, who can adjust it via the debugfs interface. In the future, a more suitable interface can be introduced and automatic removal of the reservation when the BPF scheduler is unloaded can be revisited. This patchset is also available in the following git branch: git://git.kernel.org/pub/scm/linux/kernel/git/arighi/linux.git scx-dl-server Changes in v11: - do not create/remove the bandwidth reservation for the ext server when a BPF scheduler is loaded/unloaded, but keep the reservation bandwdith always active - change rt_stall kselftest to validate both FAIR and EXT DL servers - Link to v10: https://lore.kernel.org/all/20250903095008.162049-1-arighi@nvidia.com/ Changes in v10: - reordered patches to better isolate sched_ext changes vs sched/deadline changes (Andrea Righi) - define ext_server only with CONFIG_SCHED_CLASS_EXT=y (Andrea Righi) - add WARN_ON_ONCE(!cpus) check in dl_server_apply_params() (Andrea Righi) - wait for inactive_task_timer to fire before removing the bandwidth reservation (Juri Lelli) - remove explicit dl_server_stop() in dequeue_task_scx() to reduce timer reprogramming overhead (Juri Lelli) - do not restart pick_task() when invoked by the dl_server (Tejun Heo) - rename rq_dl_server to dl_server (Peter Zijlstra) - fixed a missing dl_server start in dl_server_on() (Christian Loehle) - add a comment to the rt_stall selftest to better explain the 4% threshold (Emil Tsalapatis) - Link to v9: https://lore.kernel.org/all/20251017093214.70029-1-arighi@nvidia.com/ Changes in v9: - Drop the ->balance() logic as its functionality is now integrated into ->pick_task(), allowing dl_server to call pick_task_scx() directly - Link to v8: https://lore.kernel.org/all/20250903095008.162049-1-arighi@nvidia.com/ Changes in v8: - Add tj's patch to de-couple balance and pick_task and avoid changing sched/core callbacks to propagate @rf - Simplify dl_se->dl_server check (suggested by PeterZ) - Small coding style fixes in the kselftests - Link to v7: https://lore.kernel.org/all/20250809184800.129831-1-joelagnelf@nvidia.com/ Changes in v7: - Rebased to Linus master - Link to v6: https://lore.kernel.org/all/20250702232944.3221001-1-joelagnelf@nvidia.com/ Changes in v6: - Added Acks to few patches - Fixes to few nits suggested by Tejun - Link to v5: https://lore.kernel.org/all/20250620203234.3349930-1-joelagnelf@nvidia.com/ Changes in v5: - Added a kselftest (total_bw) to sched_ext to verify bandwidth values from debugfs - Address comment from Andrea about redundant rq clock invalidation - Link to v4: https://lore.kernel.org/all/20250617200523.1261231-1-joelagnelf@nvidia.com/ Changes in v4: - Fixed issues with hotplugged CPUs having their DL server bandwidth altered due to loading SCX - Fixed other issues - Rebased on Linus master - All sched_ext kselftests reliably pass now, also verified that the total_bw in debugfs (CONFIG_SCHED_DEBUG) is conserved with these patches - Link to v3: https://lore.kernel.org/all/20250613051734.4023260-1-joelagnelf@nvidia.com/ Changes in v3: - Removed code duplication in debugfs. Made ext interface separate - Fixed issue where rq_lock_irqsave was not used in the relinquish patch - Fixed running bw accounting issue in dl_server_remove_params - Link to v2: https://lore.kernel.org/all/20250602180110.816225-1-joelagnelf@nvidia.com/ Changes in v2: - Fixed a hang related to using rq_lock instead of rq_lock_irqsave - Added support to remove BW of DL servers when they are switched to/from EXT - Link to v1: https://lore.kernel.org/all/20250315022158.2354454-1-joelagnelf@nvidia.com/ Andrea Righi (2): sched_ext: Add a DL server for sched_ext tasks selftests/sched_ext: Add test for sched_ext dl_server Joel Fernandes (5): sched/deadline: Clear the defer params sched/debug: Fix updating of ppos on server write ops sched/debug: Stop and start server based on if it was active sched/debug: Add support to change sched_ext server params selftests/sched_ext: Add test for DL server total_bw consistency kernel/sched/core.c | 6 + kernel/sched/deadline.c | 87 +++++-- kernel/sched/debug.c | 171 +++++++++++--- kernel/sched/ext.c | 42 ++++ kernel/sched/idle.c | 3 + kernel/sched/sched.h | 2 + kernel/sched/topology.c | 5 + tools/testing/selftests/sched_ext/Makefile | 2 + tools/testing/selftests/sched_ext/rt_stall.bpf.c | 23 ++ tools/testing/selftests/sched_ext/rt_stall.c | 240 +++++++++++++++++++ tools/testing/selftests/sched_ext/total_bw.c | 281 +++++++++++++++++++++++ 11 files changed, 811 insertions(+), 51 deletions(-) create mode 100644 tools/testing/selftests/sched_ext/rt_stall.bpf.c create mode 100644 tools/testing/selftests/sched_ext/rt_stall.c create mode 100644 tools/testing/selftests/sched_ext/total_bw.c

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[PATCH] kunit: fix up const mis-match in many assert functions

by Greg Kroah-Hartman

In many kunit assert functions a const pointer is passed to container_of() and out pops a non-const pointer, which really isn't the correct thing to do at all. Fix this up by correctly marking the casted-to pointer as const to preserve the marking. Cc: Brendan Higgins <brendan.higgins(a)linux.dev> Cc: David Gow <davidgow(a)google.com> Cc: Rae Moar <raemoar63(a)gmail.com> Cc: linux-kselftest(a)vger.kernel.org Cc: kunit-dev(a)googlegroups.com Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- lib/kunit/assert.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/lib/kunit/assert.c b/lib/kunit/assert.c index 867aa5c4bccf..4c751ad8506a 100644 --- a/lib/kunit/assert.c +++ b/lib/kunit/assert.c @@ -51,7 +51,7 @@ void kunit_unary_assert_format(const struct kunit_assert *assert, const struct va_format *message, struct string_stream *stream) { - struct kunit_unary_assert *unary_assert; + const struct kunit_unary_assert *unary_assert; unary_assert = container_of(assert, struct kunit_unary_assert, assert); @@ -71,7 +71,7 @@ void kunit_ptr_not_err_assert_format(const struct kunit_assert *assert, const struct va_format *message, struct string_stream *stream) { - struct kunit_ptr_not_err_assert *ptr_assert; + const struct kunit_ptr_not_err_assert *ptr_assert; ptr_assert = container_of(assert, struct kunit_ptr_not_err_assert, assert); @@ -117,7 +117,7 @@ void kunit_binary_assert_format(const struct kunit_assert *assert, const struct va_format *message, struct string_stream *stream) { - struct kunit_binary_assert *binary_assert; + const struct kunit_binary_assert *binary_assert; binary_assert = container_of(assert, struct kunit_binary_assert, assert); @@ -145,7 +145,7 @@ void kunit_binary_ptr_assert_format(const struct kunit_assert *assert, const struct va_format *message, struct string_stream *stream) { - struct kunit_binary_ptr_assert *binary_assert; + const struct kunit_binary_ptr_assert *binary_assert; binary_assert = container_of(assert, struct kunit_binary_ptr_assert, assert); @@ -185,7 +185,7 @@ void kunit_binary_str_assert_format(const struct kunit_assert *assert, const struct va_format *message, struct string_stream *stream) { - struct kunit_binary_str_assert *binary_assert; + const struct kunit_binary_str_assert *binary_assert; binary_assert = container_of(assert, struct kunit_binary_str_assert, assert); @@ -237,7 +237,7 @@ void kunit_mem_assert_format(const struct kunit_assert *assert, const struct va_format *message, struct string_stream *stream) { - struct kunit_mem_assert *mem_assert; + const struct kunit_mem_assert *mem_assert; mem_assert = container_of(assert, struct kunit_mem_assert, assert); -- 2.52.0

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[PATCH v5 00/24] ARM64 PMU Partitioning

by Colton Lewis

This series creates a new PMU scheme on ARM, a partitioned PMU that allows reserving a subset of counters for more direct guest access, significantly reducing overhead. More details, including performance benchmarks, can be read in the v1 cover letter linked below. An overview of what this series accomplishes was presented at KVM Forum 2025. Slides [1] and video [2] are linked below. The long duration between v4 and v5 is due to time spent on this project being monopolized preparing this feature for internal production. As a result, there are too many improvements to fully list here, but I will cover the notable ones. v5: * Rebase onto v6.18-rc7. This required pulling some reorganization patches from Anish and Sean that were dependencies from previous versions based on kvm/queue but never made it to upstream. * Ensure FGTs (fine-grained traps) are correctly programmed at vCPU load using kvm_vcpu_load_fgt() and helpers introduced by Oliver Upton. * Cleanly separate concerns of whether the partitioned PMU is enabled for the guest and whether FGT should be enabled. This allows that the capability can be VM-scoped while the implementation detail of whether FGT and context switching are in effect can remain vCPU-scoped. * Shrink the uAPI change. Instead of a cap and corresponding ioctl, the feature can be controlled by just a cap with an argument. The cap is now also VM-scoped and enforces ordering that it should be decided before vCPUs are created. Whether the cap is enabled is now tracked by the new flag KVM_ARCH_ARM_PARTITIONED_PMU_ENABLED. * Improve log messages when partitioning in the PMUv3 driver. * Introduce a global variable armv8pmu_hpmn_max in the PMUv3 driver so KVM code can read if a value was set before the PMU is probed. This is needed to properly test if we have the capability before vCPUs are created. * Make it possible for a VMM to filter the HPMN0 feature bit. * Fix event filter problems with PMEVTYPER handling in writethrough_pmevtyper() and kvm_pmu_apply_event_filter() by using kvm_pmu_event_mask() in the right spots. And if an event is filtered, write the physical register with the appropriate exclude bits set but keep the virtual register exactly what the guest wrote. * Fix register access problems with the PMU register fast path handler by lifting some static PMU access checks from sys_regs.c to use them in the fast path too and make bit masking more strict for better ARM compliance. * Fix the readability and logic of programming the MDCR_EL2 register when entering the guest. Make sure to set the HPME bit to allow host counters to count guest events. Set TPM and TPMCR by default and clear them if partitioning is enabled rather than the previous inverted logic of leaving them clear and setting them if partitioning is not enabled. Make the HPMN field computation more clear. * As part of lazy context switching, do a load when the guest is switching to physical access to ensure any previous writes that only reached the virtual registers reach the physical ones as well and are not clobbered by the next vcpu_put(). * Other fixes and improvements that are too small to mention or left out from my personal notes. v4: https://lore.kernel.org/kvmarm/20250714225917.1396543-1-coltonlewis@google.… v3: https://lore.kernel.org/kvm/20250626200459.1153955-1-coltonlewis@google.com/ v2: https://lore.kernel.org/kvm/20250620221326.1261128-1-coltonlewis@google.com/ v1: https://lore.kernel.org/kvm/20250602192702.2125115-1-coltonlewis@google.com/ [1] https://gitlab.com/qemu-project/kvm-forum/-/raw/main/_attachments/2025/Opti… [2] https://www.youtube.com/watch?v=YRzZ8jMIA6M&list=PLW3ep1uCIRfxwmllXTOA2txfD… Anish Ghulati (1): KVM: arm64: Move arm_{psci,hypercalls}.h to an internal KVM path Colton Lewis (20): arm64: cpufeature: Add cpucap for HPMN0 KVM: arm64: Reorganize PMU functions perf: arm_pmuv3: Introduce method to partition the PMU perf: arm_pmuv3: Generalize counter bitmasks perf: arm_pmuv3: Keep out of guest counter partition KVM: arm64: Set up FGT for Partitioned PMU KVM: arm64: Writethrough trapped PMEVTYPER register KVM: arm64: Use physical PMSELR for PMXEVTYPER if partitioned KVM: arm64: Writethrough trapped PMOVS register KVM: arm64: Write fast path PMU register handlers KVM: arm64: Setup MDCR_EL2 to handle a partitioned PMU KVM: arm64: Account for partitioning in PMCR_EL0 access KVM: arm64: Context swap Partitioned PMU guest registers KVM: arm64: Enforce PMU event filter at vcpu_load() KVM: arm64: Implement lazy PMU context swaps perf: arm_pmuv3: Handle IRQs for Partitioned PMU guest counters KVM: arm64: Inject recorded guest interrupts KVM: arm64: Add KVM_CAP to partition the PMU KVM: selftests: Add find_bit to KVM library KVM: arm64: selftests: Add test case for partitioned PMU Marc Zyngier (1): KVM: arm64: Reorganize PMU includes Sean Christopherson (2): KVM: arm64: Include KVM headers to get forward declarations KVM: arm64: Move ARM specific headers in include/kvm to arch directory Documentation/virt/kvm/api.rst | 24 + arch/arm/include/asm/arm_pmuv3.h | 28 + arch/arm64/include/asm/arm_pmuv3.h | 61 +- .../arm64/include/asm/kvm_arch_timer.h | 2 + arch/arm64/include/asm/kvm_host.h | 24 +- .../arm64/include/asm/kvm_pmu.h | 142 ++++ arch/arm64/include/asm/kvm_types.h | 7 +- .../arm64/include/asm/kvm_vgic.h | 0 arch/arm64/kernel/cpufeature.c | 8 + arch/arm64/kvm/Makefile | 2 +- arch/arm64/kvm/arch_timer.c | 5 +- arch/arm64/kvm/arm.c | 23 +- {include => arch/arm64}/kvm/arm_hypercalls.h | 0 {include => arch/arm64}/kvm/arm_psci.h | 0 arch/arm64/kvm/config.c | 34 +- arch/arm64/kvm/debug.c | 31 +- arch/arm64/kvm/guest.c | 2 +- arch/arm64/kvm/handle_exit.c | 2 +- arch/arm64/kvm/hyp/Makefile | 6 +- arch/arm64/kvm/hyp/include/hyp/switch.h | 211 ++++- arch/arm64/kvm/hyp/nvhe/switch.c | 4 +- arch/arm64/kvm/hyp/vhe/switch.c | 4 +- arch/arm64/kvm/hypercalls.c | 4 +- arch/arm64/kvm/pmu-direct.c | 464 +++++++++++ arch/arm64/kvm/pmu-emul.c | 678 +--------------- arch/arm64/kvm/pmu.c | 726 ++++++++++++++++++ arch/arm64/kvm/psci.c | 4 +- arch/arm64/kvm/pvtime.c | 2 +- arch/arm64/kvm/reset.c | 3 +- arch/arm64/kvm/sys_regs.c | 110 +-- arch/arm64/kvm/trace_arm.h | 2 +- arch/arm64/kvm/trng.c | 2 +- arch/arm64/kvm/vgic/vgic-debug.c | 2 +- arch/arm64/kvm/vgic/vgic-init.c | 2 +- arch/arm64/kvm/vgic/vgic-irqfd.c | 2 +- arch/arm64/kvm/vgic/vgic-kvm-device.c | 2 +- arch/arm64/kvm/vgic/vgic-mmio-v2.c | 2 +- arch/arm64/kvm/vgic/vgic-mmio-v3.c | 2 +- arch/arm64/kvm/vgic/vgic-mmio.c | 4 +- arch/arm64/kvm/vgic/vgic-v2.c | 2 +- arch/arm64/kvm/vgic/vgic-v3-nested.c | 3 +- arch/arm64/kvm/vgic/vgic-v3.c | 2 +- arch/arm64/kvm/vgic/vgic-v5.c | 2 +- arch/arm64/tools/cpucaps | 1 + arch/arm64/tools/sysreg | 6 +- drivers/perf/arm_pmuv3.c | 137 +++- include/linux/perf/arm_pmu.h | 1 + include/linux/perf/arm_pmuv3.h | 14 +- include/uapi/linux/kvm.h | 1 + tools/include/uapi/linux/kvm.h | 1 + tools/testing/selftests/kvm/Makefile.kvm | 1 + .../selftests/kvm/arm64/vpmu_counter_access.c | 77 +- tools/testing/selftests/kvm/lib/find_bit.c | 1 + 53 files changed, 2049 insertions(+), 831 deletions(-) rename include/kvm/arm_arch_timer.h => arch/arm64/include/asm/kvm_arch_timer.h (98%) rename include/kvm/arm_pmu.h => arch/arm64/include/asm/kvm_pmu.h (61%) rename include/kvm/arm_vgic.h => arch/arm64/include/asm/kvm_vgic.h (100%) rename {include => arch/arm64}/kvm/arm_hypercalls.h (100%) rename {include => arch/arm64}/kvm/arm_psci.h (100%) create mode 100644 arch/arm64/kvm/pmu-direct.c create mode 100644 tools/testing/selftests/kvm/lib/find_bit.c base-commit: ac3fd01e4c1efce8f2c054cdeb2ddd2fc0fb150d -- 2.52.0.239.gd5f0c6e74e-goog

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