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    SubjectRe: [PATCH v5 bpf-next 1/3] perf: enable branch record for software events
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    Hi Peter,

    > On Sep 3, 2021, at 1:27 AM, Peter Zijlstra <peterz@infradead.org> wrote:
    >
    > On Thu, Sep 02, 2021 at 09:57:04AM -0700, Song Liu wrote:
    >
    >> +static int
    >> +intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int cnt)
    >> +{
    >> + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
    >> +
    >> + intel_pmu_disable_all();
    >> + intel_pmu_lbr_read();
    >> + cnt = min_t(unsigned int, cnt, x86_pmu.lbr_nr);
    >> +
    >> + memcpy(entries, cpuc->lbr_entries, sizeof(struct perf_branch_entry) * cnt);
    >> + intel_pmu_enable_all(0);
    >> + return cnt;
    >> +}
    >
    > Given this disables the PMI from 'random' contexts, should we not add
    > IRQ disabling around this to avoid really bad behaviour?

    Do you mean we should add (instead of not add) IRQ disable?

    Thanks,
    Song

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