On 2024/4/2 14:16, Yonghong Song wrote:
On 4/1/24 7:22 PM, Pu Lehui wrote:
On 2024/4/1 23:29, Yonghong Song wrote:
On 4/1/24 5:33 AM, Pu Lehui wrote:
From: Pu Lehui <pulehui@xxxxxxxxxx>
For the bpf selftest, the semantics of perf_event_open returning ENOENT
and EOPNOTSUPP imply that continuing the test is meaningless. Let’s
skip
test when perf_event_open returns EOPNOTSUPP, which has already been
skipped in other test cases.
Could you explain when EOPNOTSUPP is returned for these two tests?
Is this riscv specific? If the EOPNOTSUPP is returned due to missing
config in tools/testing/selftests/bpf/config, we should add that to
ensure the test can execute properly.
Hello Yonghong, I tested on riscv but it is not unique to riscv. When
the perf driver does not support sampling events, perf_event_open will
return EOPNOTSUPP, that is, PERF_PMU_CAP_NO_INTERRUPT is set to the
pmu capabilities. This is no problem with riscv with sscofpmf
extension and sbi pmu driver. I found that PERF_PMU_CAP_NO_INTERRUPT
is set not only in the riscv-related perf driver. At the same time, it
is possible to return EOPNOTSUPP about PERF_PMU_CAP_AUX_OUTPUT on the
path of perf_event_open. I think it resonable to skip such use cases
for functions not supported by non-bpf modules, what do you think?
Thanks for explanation. I checked kernel/events/core.c and arch/x86/....
I agree that if hardware has capabilities PERF_PMU_CAP_NO_INTERRUPT
or PERF_PMU_CAP_AUX_OUTPUT, EOPNOTSUPP could be returned, although I
think this should be extremely rare for x86 cpu's (probably only really
old ones).
Several other arch's also have hardware which has capability
PERF_PMU_CAP_NO_INTERRUPT, so may indeed hit this issue.
In bpf-next/arch/riscv, I didn't find usage of PERF_PMU_CAP_NO_INTERRUPT
though.
The riscv pmu driver is located in drivers/perf/riscv_pmu*. Sampling
events are not supported in legacy mode, nor in sbi mode without the
sscofpmf extension.
Your patch looks good to me. Since you hit the issue with riscv so
please describe how EOPNOTSUPP could be returned in your test. It would
be a good
justification for your patch.
Alright, I will patch that in next version.
Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
---
tools/testing/selftests/bpf/prog_tests/send_signal.c | 2 +-
.../testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c
b/tools/testing/selftests/bpf/prog_tests/send_signal.c
index b15b343ebb6b..920aee41bd58 100644
--- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
+++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
@@ -179,7 +179,7 @@ static void test_send_signal_nmi(bool
signal_thread)
pmu_fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */,
-1 /* cpu */, -1 /* group_fd */, 0 /* flags */);
if (pmu_fd == -1) {
- if (errno == ENOENT) {
+ if (errno == ENOENT || errno == EOPNOTSUPP) {
printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n",
__func__);
test__skip();
diff --git
a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
index 5db9eec24b5b..0832fd787457 100644
--- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
+++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
@@ -35,7 +35,7 @@ void test_stacktrace_build_id_nmi(void)
pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
0 /* cpu 0 */, -1 /* group id */,
0 /* flags */);
- if (pmu_fd < 0 && errno == ENOENT) {
+ if (pmu_fd < 0 && (errno == ENOENT || errno == EOPNOTSUPP)) {
printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n", __func__);
test__skip();
goto cleanup;
