Correctable memory errors are very common on servers with large
amount of memory, and are corrected by ECC, but with two
pain points to users:
1. Correction usually happens on the fly and adds latency overhead
2. Not-fully-proved theory states excessive correctable memory
errors can develop into uncorrectable memory error.
Soft offline is kernel's additional solution for memory pages
having (excessive) corrected memory errors. Impacted page is migrated
to healthy page if it is in use, then the original page is discarded
for any future use.
The actual policy on whether (and when) to soft offline should be
maintained by userspace, especially in case of HugeTLB hugepages.
Soft-offline dissolves a hugepage, either in-use or free, into
chunks of 4K pages, reducing HugeTLB pool capacity by 1 hugepage.
If userspace has not acknowledged such behavior, it may be surprised
when later mmap hugepages MAP_FAILED due to lack of hugepages.
In addition, discarding the entire 1G memory page only because of
corrected memory errors sounds very costly and kernel better not
doing under the hood. But today there are at least 2 such cases:
1. GHES driver sees both GHES_SEV_CORRECTED and
CPER_SEC_ERROR_THRESHOLD_EXCEEDED after parsing CPER.
2. RAS Correctable Errors Collector counts correctable errors per
PFN and when the counter for a PFN reaches threshold
In both cases, userspace has no control of the soft offline performed
by kernel's memory failure recovery.
This patch series give userspace the control of soft-offlining
HugeTLB pages: kernel only soft offlines hugepage if userspace has
opt-ed in for that specific hugepage size, and exposed to userspace
by a new sysfs entry called softoffline_corrected_errors under
/sys/kernel/mm/hugepages/hugepages-${size}kB directory:
* When softoffline_corrected_errors=0, skip soft offlining for all
hugepages of size ${size}kB.
* When softoffline_corrected_errors=1, soft offline as before this
patch series.
By default softoffline_corrected_errors is 1.
This patch set is based at
commit a52b4f11a2e1 ("selftest mm/mseal read-only elf memory segment").
Jiaqi Yan (3):
mm/memory-failure: userspace controls soft-offlining hugetlb pages
selftest/mm: test softoffline_corrected_errors behaviors
docs: hugetlbpage.rst: add softoffline_corrected_errors
Documentation/admin-guide/mm/hugetlbpage.rst | 15 +-
include/linux/hugetlb.h | 17 ++
mm/hugetlb.c | 34 +++
mm/memory-failure.c | 7 +
tools/testing/selftests/mm/.gitignore | 1 +
tools/testing/selftests/mm/Makefile | 1 +
.../selftests/mm/hugetlb-soft-offline.c | 262 ++++++++++++++++++
tools/testing/selftests/mm/run_vmtests.sh | 4 +
8 files changed, 340 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/mm/hugetlb-soft-offline.c
--
2.45.1.288.g0e0cd299f1-goog
The perf subsystem today unifies various tracing and monitoring
features, from both software and hardware. One benefit of the perf
subsystem is automatically inheriting events to child tasks, which
enables process-wide events monitoring with low overheads. By default
perf events are non-intrusive, not affecting behaviour of the tasks
being monitored.
For certain use-cases, however, it makes sense to leverage the
generality of the perf events subsystem and optionally allow the tasks
being monitored to receive signals on events they are interested in.
This patch series adds the option to synchronously signal user space on
events.
To better support process-wide synchronous self-monitoring, without
events propagating to children that do not share the current process's
shared environment, two pre-requisite patches are added to optionally
restrict inheritance to CLONE_THREAD, and remove events on exec (without
affecting the parent).
Examples how to use these features can be found in the tests added at
the end of the series. In addition to the tests added, the series has
also been subjected to syzkaller fuzzing (focus on 'kernel/events/'
coverage).
Motivation and Example Uses
---------------------------
1. Our immediate motivation is low-overhead sampling-based race
detection for user space [1]. By using perf_event_open() at
process initialization, we can create hardware
breakpoint/watchpoint events that are propagated automatically
to all threads in a process. As far as we are aware, today no
existing kernel facility (such as ptrace) allows us to set up
process-wide watchpoints with minimal overheads (that are
comparable to mprotect() of whole pages).
2. Other low-overhead error detectors that rely on detecting
accesses to certain memory locations or code, process-wide and
also only in a specific set of subtasks or threads.
[1] https://llvm.org/devmtg/2020-09/slides/Morehouse-GWP-Tsan.pdf
Other ideas for use-cases we found interesting, but should only
illustrate the range of potential to further motivate the utility (we're
sure there are more):
3. Code hot patching without full stop-the-world. Specifically, by
setting a code breakpoint to entry to the patched routine, then
send signals to threads and check that they are not in the
routine, but without stopping them further. If any of the
threads will enter the routine, it will receive SIGTRAP and
pause.
4. Safepoints without mprotect(). Some Java implementations use
"load from a known memory location" as a safepoint. When threads
need to be stopped, the page containing the location is
mprotect()ed and threads get a signal. This could be replaced with
a watchpoint, which does not require a whole page nor DTLB
shootdowns.
5. Threads receiving signals on performance events to
throttle/unthrottle themselves.
6. Tracking data flow globally.
Changelog
---------
v4:
* Fix for parent and child racing to exit in sync_child_event().
* Fix race between irq_work running and task's sighand being released by
release_task().
* Generalize setting si_perf and si_addr independent of event type;
introduces perf_event_attr::sig_data, which can be set by user space
to be propagated to si_perf.
* Warning in perf_sigtrap() if ctx->task and current mismatch; we expect
this on architectures that do not properly implement
arch_irq_work_raise().
* Require events that want sigtrap to be associated with a task.
* Dropped "perf: Add breakpoint information to siginfo on SIGTRAP"
in favor of more generic solution (perf_event_attr::sig_data).
v3:
* Add patch "perf: Rework perf_event_exit_event()" to beginning of
series, courtesy of Peter Zijlstra.
* Rework "perf: Add support for event removal on exec" based on
the added "perf: Rework perf_event_exit_event()".
* Fix kselftests to work with more recent libc, due to the way it forces
using the kernel's own siginfo_t.
* Add basic perf-tool built-in test.
v2/RFC: https://lkml.kernel.org/r/20210310104139.679618-1-elver@google.com
* Patch "Support only inheriting events if cloned with CLONE_THREAD"
added to series.
* Patch "Add support for event removal on exec" added to series.
* Patch "Add kselftest for process-wide sigtrap handling" added to
series.
* Patch "Add kselftest for remove_on_exec" added to series.
* Implicitly restrict inheriting events if sigtrap, but the child was
cloned with CLONE_CLEAR_SIGHAND, because it is not generally safe if
the child cleared all signal handlers to continue sending SIGTRAP.
* Various minor fixes (see details in patches).
v1/RFC: https://lkml.kernel.org/r/20210223143426.2412737-1-elver@google.com
Pre-series: The discussion at [2] led to the changes in this series. The
approach taken in "Add support for SIGTRAP on perf events" to trigger
the signal was suggested by Peter Zijlstra in [3].
[2] https://lore.kernel.org/lkml/CACT4Y+YPrXGw+AtESxAgPyZ84TYkNZdP0xpocX2jwVAbZ…
[3] https://lore.kernel.org/lkml/YBv3rAT566k+6zjg@hirez.programming.kicks-ass.n…
Marco Elver (9):
perf: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children
perf: Support only inheriting events if cloned with CLONE_THREAD
perf: Add support for event removal on exec
signal: Introduce TRAP_PERF si_code and si_perf to siginfo
perf: Add support for SIGTRAP on perf events
selftests/perf_events: Add kselftest for process-wide sigtrap handling
selftests/perf_events: Add kselftest for remove_on_exec
tools headers uapi: Sync tools/include/uapi/linux/perf_event.h
perf test: Add basic stress test for sigtrap handling
Peter Zijlstra (1):
perf: Rework perf_event_exit_event()
arch/m68k/kernel/signal.c | 3 +
arch/x86/kernel/signal_compat.c | 5 +-
fs/signalfd.c | 4 +
include/linux/compat.h | 2 +
include/linux/perf_event.h | 9 +-
include/linux/signal.h | 1 +
include/uapi/asm-generic/siginfo.h | 6 +-
include/uapi/linux/perf_event.h | 12 +-
include/uapi/linux/signalfd.h | 4 +-
kernel/events/core.c | 302 +++++++++++++-----
kernel/fork.c | 2 +-
kernel/signal.c | 11 +
tools/include/uapi/linux/perf_event.h | 12 +-
tools/perf/tests/Build | 1 +
tools/perf/tests/builtin-test.c | 5 +
tools/perf/tests/sigtrap.c | 150 +++++++++
tools/perf/tests/tests.h | 1 +
.../testing/selftests/perf_events/.gitignore | 3 +
tools/testing/selftests/perf_events/Makefile | 6 +
tools/testing/selftests/perf_events/config | 1 +
.../selftests/perf_events/remove_on_exec.c | 260 +++++++++++++++
tools/testing/selftests/perf_events/settings | 1 +
.../selftests/perf_events/sigtrap_threads.c | 210 ++++++++++++
23 files changed, 924 insertions(+), 87 deletions(-)
create mode 100644 tools/perf/tests/sigtrap.c
create mode 100644 tools/testing/selftests/perf_events/.gitignore
create mode 100644 tools/testing/selftests/perf_events/Makefile
create mode 100644 tools/testing/selftests/perf_events/config
create mode 100644 tools/testing/selftests/perf_events/remove_on_exec.c
create mode 100644 tools/testing/selftests/perf_events/settings
create mode 100644 tools/testing/selftests/perf_events/sigtrap_threads.c
--
2.31.0.208.g409f899ff0-goog
Hi,
This builds on the proposal[1] from Mark and lets me convert the
existing usercopy selftest to KUnit. Besides adding this basic test to
the KUnit collection, it also opens the door for execve testing (which
depends on having a functional current->mm), and should provide the
basic infrastructure for adding Mark's much more complete usercopy tests.
-Kees
[1] https://lore.kernel.org/lkml/20230321122514.1743889-2-mark.rutland@arm.com/
Kees Cook (2):
kunit: test: Add vm_mmap() allocation resource manager
usercopy: Convert test_user_copy to KUnit test
MAINTAINERS | 1 +
include/kunit/test.h | 17 ++
lib/Kconfig.debug | 21 +-
lib/Makefile | 2 +-
lib/kunit/test.c | 139 +++++++++++-
lib/{test_user_copy.c => usercopy_kunit.c} | 252 ++++++++++-----------
6 files changed, 288 insertions(+), 144 deletions(-)
rename lib/{test_user_copy.c => usercopy_kunit.c} (52%)
--
2.34.1
This series fixes build errors found by clang to allow the x86 suite to
get built with the clang.
Unfortunately, there is one bug [1] in the clang becuase of which
extended asm isn't handled correctly by it and build fails for
sysret_rip.c. Hence even after this series the build of this test would
fail with clang. Should we disable this test for now when clang is used
until the bug is fixed in clang? Not sure. Any opinions?
[1] https://github.com/llvm/llvm-project/issues/53728
Muhammad Usama Anjum (8):
selftests: x86: Remove dependence of headers file
selftests: x86: check_initial_reg_state: remove -no-pie while using
-static
selftests: x86: test_vsyscall: remove unused function
selftests: x86: fsgsbase_restore: fix asm directive from =rm to =r
selftests: x86: syscall_arg_fault_32: remove unused variable
selftests: x86: test_FISTTP: use fisttps instead of ambigous fisttp
selftests: x86: fsgsbase: Remove unused function and variable
selftests: x86: amx: Remove unused functions
tools/testing/selftests/x86/Makefile | 9 +++++----
tools/testing/selftests/x86/amx.c | 16 ----------------
tools/testing/selftests/x86/fsgsbase.c | 6 ------
tools/testing/selftests/x86/fsgsbase_restore.c | 2 +-
tools/testing/selftests/x86/syscall_arg_fault.c | 1 -
tools/testing/selftests/x86/test_FISTTP.c | 8 ++++----
tools/testing/selftests/x86/test_vsyscall.c | 5 -----
7 files changed, 10 insertions(+), 37 deletions(-)
--
2.39.2
in the main function of vdso_restorer.c,there is a dlopen function,
but there is no dlclose function to close the file
Signed-off-by: liujing <liujing(a)cmss.chinamobile.com>
---
tools/testing/selftests/x86/vdso_restorer.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/tools/testing/selftests/x86/vdso_restorer.c b/tools/testing/selftests/x86/vdso_restorer.c
index fe99f2434155..a0b1155dee31 100644
--- a/tools/testing/selftests/x86/vdso_restorer.c
+++ b/tools/testing/selftests/x86/vdso_restorer.c
@@ -57,6 +57,8 @@ int main()
return 0;
}
+ dlclose(vdso);
+
memset(&sa, 0, sizeof(sa));
sa.handler = handler_with_siginfo;
sa.flags = SA_SIGINFO;
--
2.18.2
Conform individual tests to TAP output. One patch conform one test. With
this series, all vDSO tests become TAP conformant.
Muhammad Usama Anjum (4):
kselftests: vdso: vdso_test_clock_getres: conform test to TAP output
kselftests: vdso: vdso_test_correctness: conform test to TAP output
kselftests: vdso: vdso_test_getcpu: conform test to TAP output
kselftests: vdso: vdso_test_gettimeofday: conform test to TAP output
.../selftests/vDSO/vdso_test_clock_getres.c | 68 ++++----
.../selftests/vDSO/vdso_test_correctness.c | 146 +++++++++---------
.../testing/selftests/vDSO/vdso_test_getcpu.c | 16 +-
.../selftests/vDSO/vdso_test_gettimeofday.c | 23 +--
4 files changed, 126 insertions(+), 127 deletions(-)
--
2.39.2
The kselftests may be built in a couple different ways:
make LLVM=1
make CC=clang
In order to handle both cases, set LLVM=1 if CC=clang. That way,the rest
of lib.mk, and any Makefiles that include lib.mk, can base decisions
solely on whether or not LLVM is set.
Then, build upon that to disable a pair of clang warnings that are
already silenced on gcc.
Doing it this way is much better than the piecemeal approach that I
started with in [1] and [2]. Thanks to Nathan Chancellor for the patch
reviews that led to this approach.
Changes since the first version:
1) Wrote a detailed explanation for suppressing two clang warnings, in
both a lib.mk comment, and the commit description.
2) Added a Reviewed-by tag to the first patch.
[1] https://lore.kernel.org/20240527214704.300444-1-jhubbard@nvidia.com
[2] https://lore.kernel.org/20240527213641.299458-1-jhubbard@nvidia.com
John Hubbard (2):
selftests/lib.mk: handle both LLVM=1 and CC=clang builds
selftests/lib.mk: silence some clang warnings that gcc already ignores
tools/testing/selftests/lib.mk | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
base-commit: e0cce98fe279b64f4a7d81b7f5c3a23d80b92fbc
--
2.45.1