[PATCH bpf v2] selftests/bpf: skip nmi test when perf hw events are disabled

[Ilya Leoshkevich]

Some setups (e.g. virtual machines) might run with hardware perf events
disabled. If this is the case, skip the test_send_signal_nmi test.

Add a separate test involving a software perf event. This allows testing
the perf event path regardless of hardware perf event support.

Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
---

v1->v2: Skip the test instead of using a software event.
Add a separate test with a software event.

 .../selftests/bpf/prog_tests/send_signal.c    | 33 ++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c 
b/tools/testing/selftests/bpf/prog_tests/send_signal.c
index 67cea1686305..54218ee3c004 100644
--- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
+++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
@@ -173,6 +173,18 @@ static int test_send_signal_tracepoint(void)
        return test_send_signal_common(&attr, BPF_PROG_TYPE_TRACEPOINT, 
"tracepoint");
 }
 
+static int test_send_signal_perf(void)
+{
+       struct perf_event_attr attr = {
+               .sample_period = 1,
+               .type = PERF_TYPE_SOFTWARE,
+               .config = PERF_COUNT_SW_CPU_CLOCK,
+       };
+
+       return test_send_signal_common(&attr, BPF_PROG_TYPE_PERF_EVENT,
+                                      "perf_sw_event");
+}
+
 static int test_send_signal_nmi(void)
 {
        struct perf_event_attr attr = {
@@ -181,8 +193,26 @@ static int test_send_signal_nmi(void)
                .type = PERF_TYPE_HARDWARE,
                .config = PERF_COUNT_HW_CPU_CYCLES,
        };
+       int pmu_fd;
+
+       /* Some setups (e.g. virtual machines) might run with hardware
+        * perf events disabled. If this is the case, skip this test.
+        */
+       pmu_fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */,
+                        -1 /* cpu */, -1 /* group_fd */, 0 /* flags */);
+       if (pmu_fd == -1) {
+               if (errno == ENOENT) {
+                       printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n",
+                               __func__);
+                       return 0;
+               }
+               /* Let the test fail with a more informative message */
+       } else {
+               close(pmu_fd);
+       }
 
-       return test_send_signal_common(&attr, BPF_PROG_TYPE_PERF_EVENT, 
"perf_event");
+       return test_send_signal_common(&attr, BPF_PROG_TYPE_PERF_EVENT,
+                                      "perf_hw_event");
 }
 
 void test_send_signal(void)
@@ -190,6 +220,7 @@ void test_send_signal(void)
        int ret = 0;
 
        ret |= test_send_signal_tracepoint();
+       ret |= test_send_signal_perf();
        ret |= test_send_signal_nmi();
        if (!ret)
                printf("test_send_signal:OK\n");
-- 
2.21.0