On Wed, Oct 6, 2021 at 1:32 PM Song Liu <songliubraving@xxxxxx> wrote:
>
> VMs running on latest kernel support LBR. However, bpf_get_branch_snapshot
> couldn't stop the LBR before too many entries are flushed. Skip the test
> for VMs before we find a proper fix for VMs.
>
> Read the "flags" line from /proc/cpuinfo, if it contains "hypervisor",
> skip test get_branch_snapshot.
Forgot to use --subject-prefix. This applies to bpf-next.
Thanks,
Song
>
> Fixes: 025bd7c753aa (selftests/bpf: Add test for bpf_get_branch_snapshot)
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
> .../bpf/prog_tests/get_branch_snapshot.c | 32 +++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
> index 67e86f8d86775..bf9d47a859449 100644
> --- a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
> +++ b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
> @@ -6,6 +6,30 @@
> static int *pfd_array;
> static int cpu_cnt;
>
> +static bool is_hypervisor(void)
> +{
> + char *line = NULL;
> + bool ret = false;
> + size_t len;
> + FILE *fp;
> +
> + fp = fopen("/proc/cpuinfo", "r");
> + if (!fp)
> + return false;
> +
> + while (getline(&line, &len, fp) != -1) {
> + if (strstr(line, "flags") == line) {
> + if (strstr(line, "hypervisor") != NULL)
> + ret = true;
> + break;
> + }
> + }
> +
> + free(line);
> + fclose(fp);
> + return ret;
> +}
> +
> static int create_perf_events(void)
> {
> struct perf_event_attr attr = {0};
> @@ -54,6 +78,14 @@ void test_get_branch_snapshot(void)
> struct get_branch_snapshot *skel = NULL;
> int err;
>
> + if (is_hypervisor()) {
> + /* As of today, LBR in hypervisor cannot be stopped before
> + * too many entries are flushed. Skip the test for now in
> + * hypervisor until we optimize the LBR in hypervisor.
> + */
> + test__skip();
> + return;
> + }
> if (create_perf_events()) {
> test__skip(); /* system doesn't support LBR */
> goto cleanup;
> --
> 2.30.2
>
