linux-kernel - Re: [PATCH v8 bpf-next 2/2] selftests/bpf: add bpf_read_branch

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Date:   Wed, 19 Feb 2020 14:47:28 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Daniel Xu <dxu@...uu.xyz>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Team <kernel-team@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH v8 bpf-next 2/2] selftests/bpf: add bpf_read_branch_records()
 selftest

On Mon, Feb 17, 2020 at 7:04 PM Daniel Xu <dxu@...uu.xyz> wrote:
>
> Add a selftest to test:
>
> * default bpf_read_branch_records() behavior
> * BPF_F_GET_BRANCH_RECORDS_SIZE flag behavior
> * error path on non branch record perf events
> * using helper to write to stack
> * using helper to write to global
>
> On host with hardware counter support:
>
>     # ./test_progs -t perf_branches
>     #27/1 perf_branches_hw:OK
>     #27/2 perf_branches_no_hw:OK
>     #27 perf_branches:OK
>     Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED
>
> On host without hardware counter support (VM):
>
>     # ./test_progs -t perf_branches
>     #27/1 perf_branches_hw:OK
>     #27/2 perf_branches_no_hw:OK
>     #27 perf_branches:OK
>     Summary: 1/2 PASSED, 1 SKIPPED, 0 FAILED

That's not what I see:
./test_progs -t perf_branches
test_perf_branches_hw:FAIL:perf_event_open err -1
#27/1 perf_branches_hw:FAIL
#27/2 perf_branches_no_hw:OK
#27 perf_branches:FAIL
Summary: 0/1 PASSED, 0 SKIPPED, 2 FAILED

I remember previous version used to work, but something changed.