On Sun, Jan 26, 2020 at 04:50:14AM +0000, Yonghong Song wrote: > > > On 1/25/20 8:10 PM, Daniel Xu wrote: > > On Sat Jan 25, 2020 at 6:53 PM, Alexei Starovoitov wrote: > >> On Sat, Jan 25, 2020 at 2:32 PM Daniel Xu <dxu@xxxxxxxxx> wrote: > >>> + attr.type = PERF_TYPE_HARDWARE; > >>> + attr.config = PERF_COUNT_HW_CPU_CYCLES; > >>> + attr.freq = 1; > >>> + attr.sample_freq = 4000; > >>> + attr.sample_type = PERF_SAMPLE_BRANCH_STACK; > >>> + attr.branch_sample_type = PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY; > >>> + pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC); > >>> + if (CHECK(pfd < 0, "perf_event_open", "err %d\n", pfd)) > >>> + goto out_destroy; > >> > >> > >> It's failing for me in kvm. Is there way to make it work? > >> CIs will be vm based too. If this test requires physical host > >> such test will keep failing in all such environments. > >> Folks will be annoyed and eventually will disable the test. > >> Can we figure out how to test in the vm from the start? > > > > It seems there's a patchset that's adding LBR support to guest hosts: > > https://lkml.org/lkml/2019/8/6/215 . However it seems to be stuck in > > review limbo. Is there anything we can do to help that set along? > > > > As far as hacking it, nothing really comes to mind. Seems that patchset > > is our best hope. > > prog_tests/send_signal.c tests send_signal helper under nmi with > hardware counters. It added a check to see whether the underlying > hardware counter is supported, if it is not, the test is > skipped. > > Maybe we can use the same appraoch here. If perf_event_open with > PERF_TYPE_HARDWARE/PERF_SAMPLE_BRANCH_STACK failed, > we just mark the test as skipped instead of failing. Instead of failing and skipping the test how about making it test error case? Like instead of lbr perf_event some other event can be passed into bpf prog. New helper can still be called and in such case it should return einval?
