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KVM: x86/pmu: Prevent zero period event from being repeatedly released

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The current vPMU can reuse the same pmc->perf_event for the same
hardware event via pmc_pause/resume_counter(), but this optimization
does not apply to a portion of the TSX events (e.g., "event=0x3c,in_tx=1,
in_tx_cp=1"), where event->attr.sample_period is legally zero at creation,
thus making the perf call to perf_event_period() meaningless (no need to
adjust sample period in this case), and instead causing such reusable
perf_events to be repeatedly released and created.

Avoid releasing zero sample_period events by checking is_sampling_event()
to follow the previously enable/disable optimization.

Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20221207071506.15733-2-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Like Xu 2022-12-07 15:15:05 +08:00 committed by Paolo Bonzini
parent 549a715b98
commit 55c590adfe
2 changed files with 4 additions and 2 deletions
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3
arch/x86/kvm/pmu.c
View File

@ -238,7 +238,8 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc)
return false;
/* recalibrate sample period and check if it's accepted by perf core */
if (perf_event_period(pmc->perf_event,
if (is_sampling_event(pmc->perf_event) &&
perf_event_period(pmc->perf_event,
get_sample_period(pmc, pmc->counter)))
return false;

3
arch/x86/kvm/pmu.h
View File

@ -140,7 +140,8 @@ static inline u64 get_sample_period(struct kvm_pmc *pmc, u64 counter_value)
static inline void pmc_update_sample_period(struct kvm_pmc *pmc)
{
if (!pmc->perf_event || pmc->is_paused)
if (!pmc->perf_event || pmc->is_paused ||
!is_sampling_event(pmc->perf_event))
return;
perf_event_period(pmc->perf_event,