On 1/25/20 8:52 PM, Alexei Starovoitov wrote: > 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? We can have both, I think. Some people may have a test environment where PERF_SAMPLE_BRANCH_STACK is available, if there is a breakage, then it will be reported.
