Add a test which checks that the RSS table is at least 4x the max
queue count supported by the device. The original RSS spec from
Microsoft stated that the RSS indirection table should be 2 to 8
times the CPU count, presumably assuming queue per CPU. If the
CPU count is not a power of two, however, a power-of-2 table
2x larger than queue count results in a 33% traffic imbalance.
Validate that the indirection table is at least 4x the queue
count. This lowers the imbalance to 16% which empirically
appears to be more acceptable to memcache-like workloads.
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260131225454.1225151-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The init_enable_count test is flaky. The test forks 1024 children before
attaching the scheduler to verify that existing tasks get ops.init_task()
called. The children were using sleep(1) before exiting.
7900aa699c ("sched_ext: Fix cgroup exit ordering by moving sched_ext_free()
to finish_task_switch()") changed when tasks are removed from scx_tasks -
previously when the task_struct was freed, now immediately in
finish_task_switch() when the task dies.
Before the commit, pre-forked children would linger on scx_tasks until freed
regardless of when they exited, so the scheduler would always see them during
iteration. The sleep(1) was unnecessary. After the commit, children are
removed as soon as they die. The sleep(1) masks the problem in most cases but
the test becomes flaky depending on timing.
Fix by synchronizing properly using a pipe. All children block on read() and
the parent signals them to exit by closing the write end after attaching the
scheduler. The children are auto-reaped so there's no need to wait on them.
Reported-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: David Vernet <void@manifault.com>
Cc: Andrea Righi <arighi@nvidia.com>
Cc: Changwoo Min <changwoo@igalia.com>
Cc: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixup and refactor downstream port enumeration to prepare for CXL port
protocol error handling. Main motivation is to move endpoint
component register mapping to a port object.
cxl/port: Unify endpoint and switch port lookup
cxl/port: Move endpoint component register management to cxl_port
cxl/port: Map Port RAS registers
cxl/port: Move dport RAS setup to dport add time
cxl/port: Move dport probe operations to a driver event
cxl/port: Move decoder setup before dport creation
cxl/port: Cleanup dport removal with a devres group
cxl/port: Reduce number of @dport variables in cxl_port_add_dport()
cxl/port: Cleanup handling of the nr_dports 0 -> 1 transition
Towards the end goal of making all CXL RAS capability handling uniform
across host bridge ports, upstream switch ports, and endpoint ports, move
dport RAS setup. Move it to cxl_switch_port_probe() context for switch / VH
dports (via cxl_port_add_dport()) and cxl_endpoint_port_probe() context for
an RCH dport. Rename the RAS setup helper to devm_cxl_dport_ras_setup() for
symmetry with devm_cxl_switch_port_decoders_setup().
Only the RCH version needs to be exported and the cxl_test mocking can be
deleted with a dev_is_pci() check on the dport_dev.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Terry Bowman <terry.bowman@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://patch.msgid.link/20260131000403.2135324-7-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
In preparation for adding more register setup to the cxl_port_add_dport()
path (for RAS register mapping), move the dport creation event to a driver
callback. This achieves two goals, it puts driver operations logically
where they belong, in a driver, and it obviates the gymnastics of
DECLARE_TESTABLE() which just makes a mess of grepping for CXL symbols.
In other words, a driver callback is less of an ongoing maintenance burden
than this DECLARE_TESTABLE arrangement that does not scale and diminishes
the grep-ability of the codebase.
cxl_port_add_dport() moves mostly unmodified from drivers/cxl/core/port.c.
The only deliberate change is that it now assumes that the device_lock is
held on entry and the driver is attached (just like cxl_port_probe()).
Reviewed-by: Terry Bowman <terry.bowman@amd.com>
Tested-by: Terry Bowman <terry.bowman@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://patch.msgid.link/20260131000403.2135324-6-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
At present the mm selftests are integrated into the kselftest harness by
having it run run_vmtest.sh and letting it pick it's default set of tests
to invoke, rather than by telling the kselftest framework about each test
program individually as is more standard. This has some unfortunate
interactions with the kselftest harness:
- If any of the tests hangs the harness will kill the entire mm
selftests run rather than just the individual test, meaning no
further tests get run.
- The timeout applied by the harness is applied to the whole run rather
than an individual test which frequently leads to the suite not being
completed in production testing.
Deploy a crude but effective mitigation for these issues by telling the
kselftest framework to run each of the test categories that run_vmtests.sh
has separately. Since kselftest really wants to run test programs this is
done by providing a trivial wrapper script for each categorty that invokes
run_vmtest.sh, this is not a thing of great elegence but it is clear and
simple. Since run_vmtests.sh is doing runtime support detection, scenario
enumeration and setup for many of the tests we can't consistently tell the
framework about the individual test programs.
This has the side effect of reordering the tests, hopefully the testing
is not overly sensitive to this.
Link: https://lkml.kernel.org/r/20260123-selftests-mm-run-suites-separately-v2-1-3e934edacbfa@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When the test fails, it shows whole sampled working set size measurements.
The purpose is showing the distribution of the measured values, to let
the tester know if it was just intermittent failure. Multiple same values
on the output are therefore unnecessary. It was not a big deal since the
test was failing only once in the past. But the test can now fail
multiple times with increased working set size, until it passes or the
working set size reaches a limit. Hence the noisy output can be quite
long and annoying. Print only the deduplicated distribution information.
Link: https://lkml.kernel.org/r/20260117020731.226785-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMON selftest for working set size estimation collects DAMON's working
set size measurements of the running artificial memory access generator
program until the program is finished. Depending on how quickly the
program finishes, and how quickly DAMON starts, the number of collected
working set size measurements may vary, and make the test results
unreliable. Ensure it collects 40 measurements by using the repeat mode
of the artificial memory access generator program, and finish the
measurements only after the desired number of collections are made.
Link: https://lkml.kernel.org/r/20260117020731.226785-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
'access_memory' is an artificial memory access generator program that is
used for a few DAMON selftests. It accesses a given number of regions one
by one only once, and exits. Depending on systems, the test workload may
exit faster than expected, making the tests unreliable. For reliable
control of the artificial memory access pattern, add a mode to make it
repeat running.
Link: https://lkml.kernel.org/r/20260117020731.226785-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMON reads and writes Accessed bits of page tables without manual TLB
flush for two reasons. First, it minimizes the overhead. Second, real
systems that need DAMON are expected to be memory intensive enough to
cause periodic TLB flushes. For test setups that use small test
workloads, however, the system's TLB could be big enough to cover whole or
most accesses of the test workload. In this case, no page table walk
happens and DAMON cannot show any access from the test workload.
The test workload for DAMON's working set size estimation selftest is such
a case. It accesses only 10 MiB working set, and it turned out there are
test setups that have TLBs large enough to cover the 10 MiB data accesses.
As a result, the test fails depending on the test machine.
Make it more reliable by trying larger working sets up to 160 MiB when it
fails.
Link: https://lkml.kernel.org/r/20260117020731.226785-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "selftests/damon: improve leak detection and wss estimation
reliability".
Two DAMON selftets, namely 'sysfs_memcg_leak' and
'sysfs_update_schemes_tried_regions_wss_estimation' frequently show
intermittent failures due to their unreliable leak detection and working
set size estimation. Make those more reliable.
This patch (of 5):
sysfs_memcg_path_leak.sh determines if the memory leak has happened by
seeing if Slab size on /proc/meminfo increases more than expected after an
action. Depending on the system and background workloads, the reasonable
expectation varies. For the reason, the test frequently shows
intermittent failures. Use kmemleak, which is much more reliable and
correct, instead.
Link: https://lkml.kernel.org/r/20260117020731.226785-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20260117020731.226785-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This self test is asserting internal implementation details and is highly
vulnerable to internal kernel changes as a result.
It is currently failing locally from at least v6.17, and it seems that it
may have been failing for longer in many configurations/hardware as it
skips if e.g. CONFIG_ANON_VMA_NAME is not specified.
With these skips and the fact that run_vmtests.sh won't run the tests in
certain configurations it is likely we have simply missed this test being
broken in CI for a long while.
I have tried multiple versions of these tests and am unable to find a
working bisect as previous versions of the test fail also.
The tests are essentially mmap()'ing a series of mappings with no hint and
asserting what the get_unmapped_area*() functions will come up with, with
seemingly few checks for what other mappings may already be in place.
It then appears to be mmap()'ing with a hint, and making a series of
similar assertions about the internal implementation details of the
hinting logic.
Commit 0ef3783d75 ("selftests/mm: add support to test 4PB VA on PPC64"),
commit 3bd6137220 ("selftests/mm: virtual_address_range: avoid reading
from VM_IO mappings"), and especially commit a005145b9c ("selftests/mm:
virtual_address_range: mmap() without PROT_WRITE") are good examples of
the whack-a-mole nature of maintaining this test.
The last commit there being particularly pertinent as it was accounting
for an internal implementation detail change that really should have no
bearing on self-tests, that is commit e93d2521b2 ("x86/vdso: Split
virtual clock pages into dedicated mapping").
The purpose of the mm self-tests are to assert attributes about the API
exposed to users, and to ensure that expectations are met.
This test is emphatically not doing this, rather making a series of
assumptions about internal implementation details and asserting them.
It therefore, sadly, seems that the best course is to remove this test
altogether.
Link: https://lkml.kernel.org/r/20260116132053.857887-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
pfnmap currently checks the target file in FIXTURE_SETUP(pfnmap), meaning
once for every test, and skips the test if any check fails.
The target file is the same for every test so this is a little overkill.
More importantly, this approach means that the whole suite will report
PASS even if all the tests are skipped because kernel configuration (e.g.
CONFIG_STRICT_DEVMEM=y) prevented /dev/mem from being mapped, for
instance.
Let's ensure that KSFT_SKIP is returned as exit code if any check fails by
performing the checks in pfnmap_init(), run once. That function also
takes care of finding the offset of the pages to be mapped and saves it in
a global. The file is now opened only once and the fd saved in a global,
but it is still mapped/unmapped for every test, as some of them modify the
mapping.
Link: https://lkml.kernel.org/r/20260122170224.4056513-10-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Usama Anjum <Usama.Anjum@arm.com>
Cc: wang lian <lianux.mm@gmail.com>
Cc: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Various mm kselftests improvements/fixes", v3.
Various improvements/fixes for the mm kselftests:
- Patch 1-3 extend support for more build configurations: out-of-tree
$KDIR, cross-compilation, etc.
- Patch 4-7 fix issues related to faulting in pages, introducing a new
helper for that purpose.
- Patch 8 fixes the value returned by pagemap_ioctl (PASS was always
returned, which explains why the issue fixed in patch 6 went
unnoticed).
- Patch 9 improves the exit code of pfnmap.
Net results:
- 1 test no longer fails (patch 7)
- 3 tests are no longer skipped (patch 4)
- More accurate return values for whole suites (patch 8, 9)
- Extra tests are more likely to be built (patch 1-3)
This patch (of 9):
KDIR currently defaults to the running kernel's modules directory when
building the page_frag module. The underlying assumption is that most
users build the kselftests in order to run them against the system they're
built on.
This assumption seems questionable, and there is no guarantee that the
module can actually be built against the running kernel.
Switch the default value of KDIR to the kernel's build directory, i.e.
$(O) if O= or KBUILD_OUTPUT= is used, and the source directory otherwise.
This seems like the least surprising option: the test module is built
against the kernel that has been previously built.
Note: we can't use $(top_srcdir) in mm/Makefile because it is only defined
once lib.mk is included.
Link: https://lkml.kernel.org/r/20260122170224.4056513-1-kevin.brodsky@arm.com
Link: https://lkml.kernel.org/r/20260122170224.4056513-2-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Usama Anjum <Usama.Anjum@arm.com>
Cc: wang lian <lianux.mm@gmail.com>
Cc: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Remove test_generic_01.sh since block layer may reorder I/O, making
the test prone to false positives. Apply the improvements to
test_generic_02.sh instead, which supposes for covering ublk dispatch
io order.
Rework test_generic_02 to verify that ublk dispatch doesn't reorder I/O
by comparing request start order with completion order using bpftrace.
The bpftrace script now:
- Tracks each request's start sequence number in a map keyed by sector
- On completion, verifies the request's start order matches expected
completion order
- Reports any out-of-order completions detected
The test script:
- Wait bpftrace BEGIN code block is run
- Pins fio to CPU 0 for deterministic behavior
- Uses block_io_start and block_rq_complete tracepoints
- Checks bpftrace output for reordering errors
Reported-and-tested-by: Alexander Atanasov <alex@zazolabs.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When running tests in parallel with high JOBS count (e.g., JOBS=64),
the existing timeouts can be insufficient due to system load:
- Increase state wait loops from 20/50 to 100 iterations in
_recover_ublk_dev(), __ublk_quiesce_dev(), and __ublk_kill_daemon()
to handle slower state transitions under heavy load
- Add --timeout=20 to udevadm settle calls to prevent indefinite
hangs when udev event queue is overwhelmed by rapid device
creation/deletion
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add _ublk_sleep() helper function that uses different sleep times
depending on whether tests run in parallel or sequential mode.
Usage: _ublk_sleep <normal_secs> <parallel_secs>
Export JOBS variable from Makefile so test scripts can detect parallel
execution, and use _ublk_sleep in test_part_02.sh to handle the
partition scan delay (1s normal, 5s parallel).
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add convenient Makefile targets for running specific test groups:
- run_generic, run_batch, run_null, run_loop, run_stripe, run_stress, etc.
- run_all for running all tests
Test groups are auto-detected from TEST_PROGS using pattern matching
(test_<group>_<num>.sh -> group), and targets are generated dynamically
using define/eval templates.
Supports parallel execution via JOBS variable:
- JOBS=1 (default): sequential with kselftest TAP output
- JOBS>1: parallel execution with xargs -P
Usage examples:
make run_null # Sequential execution
make run_stress JOBS=4 # Parallel with 4 jobs
make run_all JOBS=8 # Run all tests with 8 parallel jobs
With JOBS=8, running time of `make run_all` is reduced to 2m2s from 6m5s
in my test VM.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Track device IDs in UBLK_DEVS array when created. Update
_cleanup_test() to only delete devices created by this test
instead of using 'del -a' which removes all devices.
This prepares for running tests concurrently where each test
should only clean up its own devices.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add _ublk_del_dev() to delete a specific ublk device by ID and
use it in all test scripts instead of calling UBLK_PROG directly.
Also remove unused _remove_ublk_devices() function.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Encapsulate each test case in its own function for better organization
and maintainability:
- _setup_device(): device and backfile initialization
- _test_fill_and_verify(): initial data population
- _test_corrupted_reftag(): reftag corruption detection test
- _test_corrupted_data(): data corruption detection test
- _test_bad_apptag(): apptag mismatch detection test
Also fix temp file creation to use ${UBLK_TEST_DIR}/fio_err_XXXXX instead of
creating in current directory.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Remove intermediate TDIR variable and set UBLK_TEST_DIR directly
in _prep_test(). Remove default initialization since the directory
is created dynamically when tests run.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The added fsession does not prevent running on those architectures, that
haven't added fsession support.
For example, try to run fsession tests on arm64:
test_fsession_basic:PASS:fsession_test__open_and_load 0 nsec
test_fsession_basic:PASS:fsession_attach 0 nsec
check_result:FAIL:test_run_opts err unexpected error: -14 (errno 14)
In order to prevent such errors, add bpf_jit_supports_fsession() to guard
those architectures.
Fixes: 2d419c4465 ("bpf: add fsession support")
Acked-by: Puranjay Mohan <puranjay@kernel.org>
Tested-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260131144950.16294-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Create and use a temporary directory for the files created during
test runs. If TMPDIR environment variable is set use it as a base
for the temporary directory path.
TMPDIR=/mnt/scratch make run_tests
and
TMPDIR=/mnt/scratch ./test_generic_01.sh
will place test directory under /mnt/scratch
Signed-off-by: Alexander Atanasov <alex@zazolabs.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Log test start and end time in dmesg, so generated log messages
during the test run can be linked to specific test from the test
suite.
(switch to `date +%F %T`)
Signed-off-by: Alexander Atanasov <alex@zazolabs.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The null target doesn't handle IO, so disable partition scan to avoid IO
failures caused by integrity verification during the kernel's partition
table read.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Encapsulate each test case in its own function that creates the
device, runs checks, and deletes only that device. This avoids
calling _cleanup_test multiple times.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This test exercises partition scanning behavior, so move it to
the test_part_* group for consistency.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add test_part_01.sh to test the UBLK_F_NO_AUTO_PART_SCAN feature
flag which allows suppressing automatic partition scanning during
device startup while still allowing manual partition probing.
The test verifies:
- Normal behavior: partitions are auto-detected without the flag
- With flag: partitions are not auto-detected during START_DEV
- Manual scan: blockdev --rereadpt works with the flag
Also update kublk tool to support --no_auto_part_scan option and
recognize the feature flag.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add automatic TID derivation in test_common.sh based on the script
filename. The TID is extracted by stripping the "test_" prefix and
".sh" suffix from the script name (e.g., test_loop_01.sh -> loop_01).
This removes the need for each test script to manually define TID,
reducing boilerplate and preventing potential mismatches between
the script name and TID. Scripts can still override TID after
sourcing test_common.sh if needed.
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Recent x86 kernels export __preempt_count as a ksym, while some old kernels
between v6.1 and v6.14 expose the preemption counter via
pcpu_hot.preempt_count. The existing selftest helper unconditionally
dereferenced __preempt_count, which breaks BPF program loading on such old
kernels.
Make the x86 preemption count lookup version-agnostic by:
- Marking __preempt_count and pcpu_hot as weak ksyms.
- Introducing a BTF-described pcpu_hot___local layout with
preserve_access_index.
- Selecting the appropriate access path at runtime using ksym availability
and bpf_ksym_exists() and bpf_core_field_exists().
This allows a single BPF binary to run correctly across kernel versions
(e.g., v6.18 vs. v6.13) without relying on compile-time version checks.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
Link: https://lore.kernel.org/r/20260130021843.154885-1-changwoo@igalia.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
