selftests/bpf: skip test_perf_branches_hw() on unsupported platforms

[ Upstream commit 27746aaf1b20172f0859546c4a3e82eca459f680 ]

Gracefully skip the test_perf_branches_hw subtest on platforms that
do not support LBR or require specialized perf event attributes
to enable branch sampling.

For example, AMD's Milan (Zen 3) supports BRS rather than traditional
LBR. This requires specific configurations (attr.type = PERF_TYPE_RAW,
attr.config = RETIRED_TAKEN_BRANCH_INSTRUCTIONS) that differ from the
generic setup used within this test. Notably, it also probably doesn't
hold much value to special case perf event configurations for selected
micro architectures.

Fixes: 67306f84ca78c ("selftests/bpf: Add bpf_read_branch_records() selftest")
Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20251120142059.2836181-1-mattbobrowski@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/perf_branches.c b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
index 12c4f45cee1a8eea569decaae64b44de4d7ce37c..4a17253413a3a47dbcb8a1e8ad2f3f169f6540df 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/perf_branches.c
+++ b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
@@ -116,11 +116,11 @@ static void test_perf_branches_hw(void)
        pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
 
        /*
-        * Some setups don't support branch records (virtual machines, !x86),
-        * so skip test in this case.
+        * Some setups don't support LBR (virtual machines, !x86, AMD Milan Zen
+        * 3 which only supports BRS), so skip test in this case.
         */
        if (pfd < 0) {
-               if (errno == ENOENT || errno == EOPNOTSUPP) {
+               if (errno == ENOENT || errno == EOPNOTSUPP || errno == EINVAL) {
                        printf("%s:SKIP:no PERF_SAMPLE_BRANCH_STACK\n",
                               __func__);
                        test__skip();