- Linux-kselftest-mirror - lists.linaro.org

[PATCH v2 0/4] KVM: selftests: arm64: Improve diagnostics from set_id_regs

by Mark Brown

While debugging issues related to aarch64 only systems I ran into speedbumps due to the lack of detail in the results reported when the guest register read and reset value preservation tests were run, they generated an immediately fatal assert without indicating which register was being tested. Update these tests to report a result per register, making it much easier to see what the problem being reported is. A similar, though less severe, issue exists with the validation of the individual bitfields in registers due to the use of immediately fatal asserts. Update those asserts to be standard kselftest reports. Finally we have a fix for spurious errors on some NV systems. Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v2: - Add a fix for spurious failures with 64 bit only guests. - Link to v1: https://patch.msgid.link/20251030-kvm-arm64-set-id-regs-aarch64-v1-0-96fe0d… --- Mark Brown (4): KVM: selftests: arm64: Report set_id_reg reads of test registers as tests KVM: selftests: arm64: Report register reset tests individually KVM: selftests: arm64: Make set_id_regs bitfield validatity checks non-fatal KVM: selftests: arm64: Skip all 32 bit IDs when set_id_regs is aarch64 only tools/testing/selftests/kvm/arm64/set_id_regs.c | 150 ++++++++++++++++++------ 1 file changed, 111 insertions(+), 39 deletions(-) --- base-commit: 211ddde0823f1442e4ad052a2f30f050145ccada change-id: 20251028-kvm-arm64-set-id-regs-aarch64-ebb77969401c Best regards, -- Mark Brown <broonie(a)kernel.org>

1 week, 5 days

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[PATCH v7 0/2] KVM: guest_memfd: use write for population

by Kalyazin, Nikita

On systems that support shared guest memory, write() is useful, for example, for population of the initial image. Even though the same can also be achieved via userspace mapping and memcpying from userspace, write() provides a more performant option because it does not need to set user page tables and it does not cause a page fault for every page like memcpy would. Note that memcpy cannot be accelerated via MADV_POPULATE_WRITE as it is not supported by guest_memfd and relies on GUP. Populating 512MiB of guest_memfd on a x86 machine: - via memcpy: 436 ms - via write: 202 ms (-54%) Only PAGE_ALIGNED offset and len are allowed. Even though non-aligned writes are technically possible, when in-place conversion support is implemented [1], the restriction makes handling of mixed shared/private huge pages simpler. write() will only be allowed to populate shared pages. When direct map removal is implemented [2] - write() will not be allowed to access pages that have already been removed from direct map - on completion, write() will remove the populated pages from direct map While it is technically possible to implement read() syscall on systems with shared guest memory, it is not supported as there is currently no use case for it. [1] https://lore.kernel.org/kvm/cover.1760731772.git.ackerleytng@google.com [2] https://lore.kernel.org/kvm/20250924151101.2225820-1-patrick.roy@campus.lmu… Nikita Kalyazin (2): KVM: guest_memfd: add generic population via write KVM: selftests: update guest_memfd write tests Documentation/virt/kvm/api.rst | 2 + include/linux/kvm_host.h | 2 +- include/uapi/linux/kvm.h | 1 + .../testing/selftests/kvm/guest_memfd_test.c | 58 +++++++++++++++++-- virt/kvm/guest_memfd.c | 52 +++++++++++++++++ 5 files changed, 108 insertions(+), 7 deletions(-) base-commit: 8a4821412cf2c1429fffa07c012dd150f2edf78c -- 2.50.1

1 week, 5 days

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[PATCH] kunit: Make filter parameters configurable via Kconfig

by Thomas Weißschuh

Enable the preset of filter parameters from kconfig options, similar to how other KUnit configuration parameters are handled already. This is useful to run a subset of tests even if the cmdline is not readily modifyable. Signed-off-by: Thomas Weißschuh <thomas.weissschuh(a)linutronix.de> --- lib/kunit/Kconfig | 24 ++++++++++++++++++++++++ lib/kunit/executor.c | 8 +++++--- 2 files changed, 29 insertions(+), 3 deletions(-) diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig index 7a6af361d2fc6276b9667be8c694b0c80e33c1e8..50ecf55d2b9c8a82f2aff7a0b4156bd6179b0a2f 100644 --- a/lib/kunit/Kconfig +++ b/lib/kunit/Kconfig @@ -93,6 +93,30 @@ config KUNIT_AUTORUN_ENABLED In most cases this should be left as Y. Only if additional opt-in behavior is needed should this be set to N. +config KUNIT_DEFAULT_FILTER_GLOB + string "Default value of the filter_glob module parameter" + help + Sets the default value of kunit.filter_glob. If set to a non-empty + string only matching tests are executed. + + If unsure, leave empty so all tests are executed. + +config KUNIT_DEFAULT_FILTER + string "Default value of the filter module parameter" + help + Sets the default value of kunit.filter. If set to a non-empty + string only matching tests are executed. + + If unsure, leave empty so all tests are executed. + +config KUNIT_DEFAULT_FILTER_ACTION + string "Default value of the filter_action module parameter" + help + Sets the default value of kunit.filter_action. If set to a non-empty + string only matching tests are executed. + + If unsure, leave empty so all tests are executed. + config KUNIT_DEFAULT_TIMEOUT int "Default value of the timeout module parameter" default 300 diff --git a/lib/kunit/executor.c b/lib/kunit/executor.c index 0061d4c7e35170634a3c1d1cff7179037fb8ba07..02ff380ab7938cfac2be3f8c0e7630a78961cc3d 100644 --- a/lib/kunit/executor.c +++ b/lib/kunit/executor.c @@ -45,9 +45,11 @@ bool kunit_autorun(void) return autorun_param; } -static char *filter_glob_param; -static char *filter_param; -static char *filter_action_param; +#define PARAM_FROM_CONFIG(config) (config[0] ? config : NULL) + +static char *filter_glob_param = PARAM_FROM_CONFIG(CONFIG_KUNIT_DEFAULT_FILTER_GLOB); +static char *filter_param = PARAM_FROM_CONFIG(CONFIG_KUNIT_DEFAULT_FILTER); +static char *filter_action_param = PARAM_FROM_CONFIG(CONFIG_KUNIT_DEFAULT_FILTER_ACTION); module_param_named(filter_glob, filter_glob_param, charp, 0600); MODULE_PARM_DESC(filter_glob, --- base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787 change-id: 20251106-kunit-filter-kconfig-f08998936fc6 Best regards, -- Thomas Weißschuh <thomas.weissschuh(a)linutronix.de>

1 week, 5 days

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[PATCH RESEND] selftests/futex: skip tests if shmget unsupported

by Carlos Llamas

On systems where the shmget() syscall is not supported, tests like anon_page and shared_waitv will fail. Skip these tests in such cases to allow the rest of the test suite to run. Signed-off-by: Carlos Llamas <cmllamas(a)google.com> --- tools/testing/selftests/futex/functional/futex_wait.c | 2 ++ tools/testing/selftests/futex/functional/futex_waitv.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/tools/testing/selftests/futex/functional/futex_wait.c b/tools/testing/selftests/futex/functional/futex_wait.c index 152ca4612886..1269642bb662 100644 --- a/tools/testing/selftests/futex/functional/futex_wait.c +++ b/tools/testing/selftests/futex/functional/futex_wait.c @@ -71,6 +71,8 @@ TEST(anon_page) /* Testing an anon page shared memory */ shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); if (shm_id < 0) { + if (errno == ENOSYS) + ksft_exit_skip("shmget syscall not supported\n"); perror("shmget"); exit(1); } diff --git a/tools/testing/selftests/futex/functional/futex_waitv.c b/tools/testing/selftests/futex/functional/futex_waitv.c index c684b10eb76e..3bc4e5dc70e7 100644 --- a/tools/testing/selftests/futex/functional/futex_waitv.c +++ b/tools/testing/selftests/futex/functional/futex_waitv.c @@ -86,6 +86,8 @@ TEST(shared_waitv) int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); if (shm_id < 0) { + if (errno == ENOSYS) + ksft_exit_skip("shmget syscall not supported\n"); perror("shmget"); exit(1); } -- 2.52.0.rc1.455.g30608eb744-goog

1 week, 5 days

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[PATCH net v5 0/3] mptcp: Fix conflicts between MPTCP and sockmap

by Jiayuan Chen

Overall, we encountered a warning [1] that can be triggered by running the selftest I provided. sockmap works by replacing sk_data_ready, recvmsg, sendmsg operations and implementing fast socket-level forwarding logic: 1. Users can obtain file descriptors through userspace socket()/accept() interfaces, then call BPF syscall to perform these replacements. 2. Users can also use the bpf_sock_hash_update helper (in sockops programs) to replace handlers when TCP connections enter ESTABLISHED state (BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB/BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB) However, when combined with MPTCP, an issue arises: MPTCP creates subflow sk's and performs TCP handshakes, so the BPF program obtains subflow sk's and may incorrectly replace their sk_prot. We need to reject such operations. In patch 1, we set psock_update_sk_prot to NULL in the subflow's custom sk_prot. Additionally, if the server's listening socket has MPTCP enabled and the client's TCP also uses MPTCP, we should allow the combination of subflow and sockmap. This is because the latest Golang programs have enabled MPTCP for listening sockets by default [2]. For programs already using sockmap, upgrading Golang should not cause sockmap functionality to fail. Patch 2 prevents the WARNING from occurring. Despite these patches fixing stream corruption, users of sockmap must set GODEBUG=multipathtcp=0 to disable MPTCP until sockmap fully supports it. [1] truncated warning: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 388 at net/mptcp/protocol.c:68 mptcp_stream_accept+0x34c/0x380 Modules linked in: RIP: 0010:mptcp_stream_accept+0x34c/0x380 RSP: 0018:ffffc90000cf3cf8 EFLAGS: 00010202 PKRU: 55555554 Call Trace: <TASK> do_accept+0xeb/0x190 ? __x64_sys_pselect6+0x61/0x80 ? _raw_spin_unlock+0x12/0x30 ? alloc_fd+0x11e/0x190 __sys_accept4+0x8c/0x100 __x64_sys_accept+0x1f/0x30 x64_sys_call+0x202f/0x20f0 do_syscall_64+0x72/0x9a0 ? switch_fpu_return+0x60/0xf0 ? irqentry_exit_to_user_mode+0xdb/0x1e0 ? irqentry_exit+0x3f/0x50 ? clear_bhb_loop+0x50/0xa0 ? clear_bhb_loop+0x50/0xa0 ? clear_bhb_loop+0x50/0xa0 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK> ---[ end trace 0000000000000000 ]--- [2]: https://go-review.googlesource.com/c/go/+/607715 --- v4 -> v5: Dropped redundant selftest code, updated the Fixes tag, and added a Reviewed-by tag. v3 -> v4: Addressed questions from Matthieu and Paolo, explained sockmap's operational mechanism, and finalized the changes v2 -> v3: Adopted Jakub Sitnicki's suggestions - atomic retrieval of sk_family is required v1 -> v2: Had initial discussion with Matthieu on sockmap and MPTCP technical details v4: https://lore.kernel.org/bpf/20251105113625.148900-1-jiayuan.chen@linux.dev/ v3: https://lore.kernel.org/bpf/20251023125450.105859-1-jiayuan.chen@linux.dev/ v2: https://lore.kernel.org/bpf/20251020060503.325369-1-jiayuan.chen@linux.dev/… v1: https://lore.kernel.org/mptcp/a0a2b87119a06c5ffaa51427a0964a05534fe6f1@linu… Jiayuan Chen (3): mptcp: disallow MPTCP subflows from sockmap net,mptcp: fix proto fallback detection with BPF selftests/bpf: Add mptcp test with sockmap net/mptcp/protocol.c | 6 +- net/mptcp/subflow.c | 8 + .../testing/selftests/bpf/prog_tests/mptcp.c | 141 ++++++++++++++++++ .../selftests/bpf/progs/mptcp_sockmap.c | 43 ++++++ 4 files changed, 196 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/mptcp_sockmap.c base-commit: 8c0726e861f3920bac958d76cf134b5a3aa14ce4 -- 2.43.0

1 week, 5 days

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Re: [PATCH] selftests/cgroup: conform test to TAP format output

by Sebastian Chlad

On Fri, Nov 14, 2025 at 4:59 AM Guopeng Zhang <zhangguopeng(a)kylinos.cn> wrote: > > Hi Michal, > > Thanks for reviewing and pointing out [1]. > > > Could you please explain more why is the TAP layout beneficial? > > (I understand selftest are for oneself, i.e. human readable only by default.) > > Actually, selftests are no longer just something for developers to view locally; they are now extensively > run in CI and stable branch regression testing. Using a standardized layout means that general test runners > and CI systems can parse the cgroup test results without any special handling. I second that. In fact, we do run some of those tests in the CI; i.e. https://openqa.opensuse.org/tests/5453031#external We added this: https://github.com/os-autoinst/openQA/blob/master/lib/OpenQA/Parser/Format/… to our CI but frankly the use of the KTAP across the selftests is very inconsistent, so we need to post-process some of the output files quite a lot. Therefore the more standardized the output, the better for any CI. Small ask: should we amend the commit message to say KTAP? That being said - the cgroups tests produce nice output which is easy to parse and gives us no issues in our CI apart from the shell tests, specifically test_cpuset_prs.sh. We currently run the cgroup tests only internally because some of them tend to fail when crossing resource-usage boundaries and don’t provide clear information about by how much. That ties into my earlier effort Michal linked here:: https://lore.kernel.org/all/rua6ubri67gh3b7atarbm5mggqgjyh6646mzkry2n2547jn… I’ll try to add the cgroup tests to the public openSUSE CI and will test your patches. > > TAP provides a structured format that is both human-readable and machine-readable. The plan/result lines are parsed by tools, > while the diagnostic lines can still contain human-readable debug information. Over time, other selftest suites (such as mm, KVM, mptcp, etc.) > have also been converted to TAP-style output, so this change just brings the cgroup tests in line with that broader direction. > > > Or is this part of some tree-wide effort? > > This patch is not part of a formal, tree-wide conversion series I am running; it is an incremental step to align the > cgroup C tests with the existing TAP usage. I started here because these tests already use ksft_test_result_*() and > only require minor changes to generate proper TAP output. > > > I'm asking to better asses whether also the scripts listed in > > Makefile:TEST_PROGS should be converted too. > > I agree that having them produce TAP output would benefit tooling and CI. I did not want to mix > that into this change, but if you and other maintainers think this direction is reasonable, > I would be happy to follow up and convert the cgroup shell tests to TAP as well. > > Thanks again for your review. > > Best regards, > Guopeng > >

1 week, 5 days

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[PATCH] selftests/cgroup: conform test to TAP format output

by Guopeng Zhang

Conform the layout, informational and status messages to TAP. No functional change is intended other than the layout of output messages. Signed-off-by: Guopeng Zhang <zhangguopeng(a)kylinos.cn> --- tools/testing/selftests/cgroup/test_core.c | 7 ++++--- tools/testing/selftests/cgroup/test_cpu.c | 7 ++++--- tools/testing/selftests/cgroup/test_cpuset.c | 7 ++++--- tools/testing/selftests/cgroup/test_freezer.c | 7 ++++--- tools/testing/selftests/cgroup/test_kill.c | 7 ++++--- tools/testing/selftests/cgroup/test_kmem.c | 7 ++++--- tools/testing/selftests/cgroup/test_memcontrol.c | 7 ++++--- tools/testing/selftests/cgroup/test_zswap.c | 7 ++++--- 8 files changed, 32 insertions(+), 24 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_core.c b/tools/testing/selftests/cgroup/test_core.c index 5e5b8c4b8c0e..102262555a59 100644 --- a/tools/testing/selftests/cgroup/test_core.c +++ b/tools/testing/selftests/cgroup/test_core.c @@ -923,8 +923,10 @@ struct corecg_test { int main(int argc, char *argv[]) { char root[PATH_MAX]; - int i, ret = EXIT_SUCCESS; + int i; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), &nsdelegate)) { if (setup_named_v1_root(root, sizeof(root), CG_NAMED_NAME)) ksft_exit_skip("cgroup v2 isn't mounted and could not setup named v1 hierarchy\n"); @@ -946,12 +948,11 @@ int main(int argc, char *argv[]) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } cleanup_named_v1_root(root); - return ret; + ksft_finished(); } diff --git a/tools/testing/selftests/cgroup/test_cpu.c b/tools/testing/selftests/cgroup/test_cpu.c index 7d77d3d43c8e..c83f05438d7c 100644 --- a/tools/testing/selftests/cgroup/test_cpu.c +++ b/tools/testing/selftests/cgroup/test_cpu.c @@ -796,8 +796,10 @@ struct cpucg_test { int main(int argc, char *argv[]) { char root[PATH_MAX]; - int i, ret = EXIT_SUCCESS; + int i; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) ksft_exit_skip("cgroup v2 isn't mounted\n"); @@ -814,11 +816,10 @@ int main(int argc, char *argv[]) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } - return ret; + ksft_finished(); } diff --git a/tools/testing/selftests/cgroup/test_cpuset.c b/tools/testing/selftests/cgroup/test_cpuset.c index 8094091a5857..c5cf8b56ceb8 100644 --- a/tools/testing/selftests/cgroup/test_cpuset.c +++ b/tools/testing/selftests/cgroup/test_cpuset.c @@ -247,8 +247,10 @@ struct cpuset_test { int main(int argc, char *argv[]) { char root[PATH_MAX]; - int i, ret = EXIT_SUCCESS; + int i; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) ksft_exit_skip("cgroup v2 isn't mounted\n"); @@ -265,11 +267,10 @@ int main(int argc, char *argv[]) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } - return ret; + ksft_finished(); } diff --git a/tools/testing/selftests/cgroup/test_freezer.c b/tools/testing/selftests/cgroup/test_freezer.c index 714c963aa3f5..97fae92c8387 100644 --- a/tools/testing/selftests/cgroup/test_freezer.c +++ b/tools/testing/selftests/cgroup/test_freezer.c @@ -1488,8 +1488,10 @@ struct cgfreezer_test { int main(int argc, char *argv[]) { char root[PATH_MAX]; - int i, ret = EXIT_SUCCESS; + int i; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) ksft_exit_skip("cgroup v2 isn't mounted\n"); for (i = 0; i < ARRAY_SIZE(tests); i++) { @@ -1501,11 +1503,10 @@ int main(int argc, char *argv[]) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } - return ret; + ksft_finished(); } diff --git a/tools/testing/selftests/cgroup/test_kill.c b/tools/testing/selftests/cgroup/test_kill.c index a4dd326ced79..c8c9d306925b 100644 --- a/tools/testing/selftests/cgroup/test_kill.c +++ b/tools/testing/selftests/cgroup/test_kill.c @@ -274,8 +274,10 @@ struct cgkill_test { int main(int argc, char *argv[]) { char root[PATH_MAX]; - int i, ret = EXIT_SUCCESS; + int i; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) ksft_exit_skip("cgroup v2 isn't mounted\n"); for (i = 0; i < ARRAY_SIZE(tests); i++) { @@ -287,11 +289,10 @@ int main(int argc, char *argv[]) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } - return ret; + ksft_finished(); } diff --git a/tools/testing/selftests/cgroup/test_kmem.c b/tools/testing/selftests/cgroup/test_kmem.c index 005a142f3492..ca38525484e3 100644 --- a/tools/testing/selftests/cgroup/test_kmem.c +++ b/tools/testing/selftests/cgroup/test_kmem.c @@ -421,8 +421,10 @@ struct kmem_test { int main(int argc, char **argv) { char root[PATH_MAX]; - int i, ret = EXIT_SUCCESS; + int i; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) ksft_exit_skip("cgroup v2 isn't mounted\n"); @@ -446,11 +448,10 @@ int main(int argc, char **argv) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } - return ret; + ksft_finished(); } diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index 2e9d78ab641c..4e1647568c5b 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -1650,8 +1650,10 @@ struct memcg_test { int main(int argc, char **argv) { char root[PATH_MAX]; - int i, proc_status, ret = EXIT_SUCCESS; + int i, proc_status; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) ksft_exit_skip("cgroup v2 isn't mounted\n"); @@ -1685,11 +1687,10 @@ int main(int argc, char **argv) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } - return ret; + ksft_finished(); } diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index ab865d900791..64ebc3f3f203 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -597,8 +597,10 @@ static bool zswap_configured(void) int main(int argc, char **argv) { char root[PATH_MAX]; - int i, ret = EXIT_SUCCESS; + int i; + ksft_print_header(); + ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) ksft_exit_skip("cgroup v2 isn't mounted\n"); @@ -625,11 +627,10 @@ int main(int argc, char **argv) ksft_test_result_skip("%s\n", tests[i].name); break; default: - ret = EXIT_FAILURE; ksft_test_result_fail("%s\n", tests[i].name); break; } } - return ret; + ksft_finished(); } -- 2.25.1

1 week, 5 days

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[PATCH v4 0/3] VMM can handle guest SEA via KVM_EXIT_ARM_SEA

by Jiaqi Yan

Problem ======= When host APEI is unable to claim a synchronous external abort (SEA) during guest abort, today KVM directly injects an asynchronous SError into the VCPU then resumes it. The injected SError usually results in unpleasant guest kernel panic. One of the major situation of guest SEA is when VCPU consumes recoverable uncorrected memory error (UER), which is not uncommon at all in modern datacenter servers with large amounts of physical memory. Although SError and guest panic is sufficient to stop the propagation of corrupted memory, there is room to recover from an UER in a more graceful manner. Proposed Solution ================= The idea is, we can replay the SEA to the faulting VCPU. If the memory error consumption or the fault that cause SEA is not from guest kernel, the blast radius can be limited to the poison-consuming guest process, while the VM can keep running. In addition, instead of doing under the hood without involving userspace, there are benefits to redirect the SEA to VMM: - VM customers care about the disruptions caused by memory errors, and VMM usually has the responsibility to start the process of notifying the customers of memory error events in their VMs. For example some cloud provider emits a critical log in their observability UI [1], and provides a playbook for customers on how to mitigate disruptions to their workloads. - VMM can protect future memory error consumption by unmapping the poisoned pages from stage-2 page table with KVM userfault [2], or by splitting the memslot that contains the poisoned pages. - VMM can keep track of SEA events in the VM. When VMM thinks the status on the host or the VM is bad enough, e.g. number of distinct SEAs exceeds a threshold, it can restart the VM on another healthy host. - Behavior parity with x86 architecture. When machine check exception (MCE) is caused by VCPU, kernel or KVM signals userspace SIGBUS to let VMM either recover from the MCE, or terminate itself with VM. The prior RFC proposes to implement SIGBUS on arm64 as well, but Marc preferred KVM exit over signal [3]. However, implementation aside, returning SEA to VMM is on par with returning MCE to VMM. Once SEA is redirected to VMM, among other actions, VMM is encouraged to inject external aborts into the faulting VCPU. New UAPIs ========= This patchset introduces following userspace-visible changes to empower VMM to control what happens for SEA on guest memory: - KVM_CAP_ARM_SEA_TO_USER. While taking SEA, if userspace has enabled this new capability at VM creation, and the SEA is not owned by kernel allocated memory, instead of injecting SError, return KVM_EXIT_ARM_SEA to userspace. - KVM_EXIT_ARM_SEA. This is the VM exit reason VMM gets. The details about the SEA is provided in arm_sea as much as possible, including sanitized ESR value at EL2, faulting guest virtual and physical addresses if available. * From v3 [4] - Rebased on commit 3a8660878839 ("Linux 6.18-rc1"). - In selftest, print a message if GVA or GPA expects to be valid. * From v2 [5]: - Rebased on "[PATCH] KVM: arm64: nv: Handle SEAs due to VNCR redirection" [6] and kvmarm/next commit 7b8346bd9fce6 ("KVM: arm64: Don't attempt vLPI mappings when vPE allocation is disabled") - Took the host_owns_sea implementation from Oliver [7, 8]. - Excluded the guest SEA injection patches. - Updated selftest. * From v1 [9]: - Rebased on commit 4d62121ce9b5 ("KVM: arm64: vgic-debug: Avoid dereferencing NULL ITE pointer"). - Sanitize ESR_EL2 before reporting it to userspace. - Do not do KVM_EXIT_ARM_SEA when SEA is caused by memory allocated to stage-2 translation table. [1] https://cloud.google.com/solutions/sap/docs/manage-host-errors [2] https://lore.kernel.org/kvm/20250109204929.1106563-1-jthoughton@google.com [3] https://lore.kernel.org/kvm/86pljbqqh0.wl-maz@kernel.org [4] https://lore.kernel.org/kvmarm/20250731205844.1346839-1-jiaqiyan@google.com [5] https://lore.kernel.org/kvm/20250604050902.3944054-1-jiaqiyan@google.com [6] https://lore.kernel.org/kvmarm/20250729182342.3281742-1-oliver.upton@linux.… [7] https://lore.kernel.org/kvm/aHFohmTb9qR_JG1E@linux.dev [8] https://lore.kernel.org/kvm/aHK-DPufhLy5Dtuk@linux.dev [9] https://lore.kernel.org/kvm/20250505161412.1926643-1-jiaqiyan@google.com Jiaqi Yan (3): KVM: arm64: VM exit to userspace to handle SEA KVM: selftests: Test for KVM_EXIT_ARM_SEA Documentation: kvm: new UAPI for handling SEA Documentation/virt/kvm/api.rst | 61 ++++ arch/arm64/include/asm/kvm_host.h | 2 + arch/arm64/kvm/arm.c | 5 + arch/arm64/kvm/mmu.c | 68 +++- include/uapi/linux/kvm.h | 10 + tools/arch/arm64/include/asm/esr.h | 2 + tools/testing/selftests/kvm/Makefile.kvm | 1 + .../testing/selftests/kvm/arm64/sea_to_user.c | 331 ++++++++++++++++++ tools/testing/selftests/kvm/lib/kvm_util.c | 1 + 9 files changed, 480 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/kvm/arm64/sea_to_user.c -- 2.51.0.760.g7b8bcc2412-goog

1 week, 5 days

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[PATCH v9 0/9] liveupdate: Rework KHO for in-kernel users

by Pasha Tatashin

Changelog: v9: Added review-bys and addressed comments from Mike Rapoport and Pratyush Yadav. Dropped patch that moves abort/finalize to public header per Mike's request. Added patch from Zhu Yanjun to output errors by name. This series appliyes against akpm's mm-unstable branch. This series refactors the KHO framework to better support in-kernel users like the upcoming LUO. The current design, which relies on a notifier chain and debugfs for control, is too restrictive for direct programmatic use. The core of this rework is the removal of the notifier chain in favor of a direct registration API. This decouples clients from the shutdown-time finalization sequence, allowing them to manage their preserved state more flexibly and at any time. In support of this new model, this series also: - Makes the debugfs interface optional. - Introduces APIs to unpreserve memory and fixes a bug in the abort path where client state was being incorrectly discarded. Note that this is an interim step, as a more comprehensive fix is planned as part of the stateless KHO work [1]. - Moves all KHO code into a new kernel/liveupdate/ directory to consolidate live update components. [1] https://lore.kernel.org/all/20251020100306.2709352-1-jasonmiu@google.com Mike Rapoport (Microsoft) (1): kho: drop notifiers Pasha Tatashin (7): kho: make debugfs interface optional kho: add interfaces to unpreserve folios, page ranges, and vmalloc memblock: Unpreserve memory in case of error test_kho: Unpreserve memory in case of error kho: don't unpreserve memory during abort liveupdate: kho: move to kernel/liveupdate MAINTAINERS: update KHO maintainers Zhu Yanjun (1): liveupdate: kho: Use %pe format specifier for error pointer printing Documentation/core-api/kho/concepts.rst | 2 +- MAINTAINERS | 4 +- include/linux/kexec_handover.h | 46 +- init/Kconfig | 2 + kernel/Kconfig.kexec | 24 - kernel/Makefile | 3 +- kernel/kexec_handover_internal.h | 16 - kernel/liveupdate/Kconfig | 39 ++ kernel/liveupdate/Makefile | 5 + kernel/{ => liveupdate}/kexec_handover.c | 532 +++++++----------- .../{ => liveupdate}/kexec_handover_debug.c | 0 kernel/liveupdate/kexec_handover_debugfs.c | 221 ++++++++ kernel/liveupdate/kexec_handover_internal.h | 56 ++ lib/test_kho.c | 128 +++-- mm/memblock.c | 93 +-- tools/testing/selftests/kho/vmtest.sh | 1 + 16 files changed, 690 insertions(+), 482 deletions(-) delete mode 100644 kernel/kexec_handover_internal.h create mode 100644 kernel/liveupdate/Kconfig create mode 100644 kernel/liveupdate/Makefile rename kernel/{ => liveupdate}/kexec_handover.c (80%) rename kernel/{ => liveupdate}/kexec_handover_debug.c (100%) create mode 100644 kernel/liveupdate/kexec_handover_debugfs.c create mode 100644 kernel/liveupdate/kexec_handover_internal.h base-commit: 9ef7b034116354ee75502d1849280a4d2ff98a7c -- 2.51.1.930.gacf6e81ea2-goog

1 week, 6 days

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[GIT PULL] kselftest fixes update for Linux 6.18-rc6

by Shuah Khan

Hi Linus, Please pull this kselftest fixes update for Linux 6.18-rc6 Fixes event-filter-function.tc tracing test failure caused when a first run to sample events triggers kmem_cache_free which interferes with the rest of the test. Fix this calling sample_events twice to eliminate the kmem_cache_free related noise from the sampling. diff is attached. thanks, -- Shuah ---------------------------------------------------------------- The following changes since commit 920aa3a7705a061cb3004572d8b7932b54463dbf: selftests: cachestat: Fix warning on declaration under label (2025-10-22 09:23:18 -0600) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest tags/linux_kselftest-fixes-6.18-rc6 for you to fetch changes up to dd4adb986a86727ed8f56c48b6d0695f1e211e65: selftests/tracing: Run sample events to clear page cache events (2025-11-10 18:00:07 -0700) ---------------------------------------------------------------- linux_kselftest-fixes-6.18-rc6 Fixes event-filter-function.tc tracing test failure caused when a first run to sample events triggers kmem_cache_free which interferes with the rest of the test. Fix this calling sample_events twice to eliminate the kmem_cache_free related noise from the sampling. ---------------------------------------------------------------- Steven Rostedt (1): selftests/tracing: Run sample events to clear page cache events tools/testing/selftests/ftrace/test.d/filter/event-filter-function.tc | 4 ++++ 1 file changed, 4 insertions(+) ----------------------------------------------------------------

1 week, 6 days

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