Messages in this thread | | | Date | Fri, 5 Nov 2021 15:43:14 +0800 | From | Like Xu <> | Subject | Re: [PATCH] perf/x86/lbr: Reset LBR_SELECT during vlbr reset |
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On 5/11/2021 3:20 pm, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > lbr_select in kvm guest has residual data even if kvm guest is poweroff. > We can get residual data in the next boot. Because lbr_select is not > reset during kvm vlbr release. Let's reset LBR_SELECT during vlbr reset.
This is because when a new vlbr event is first scheduled in the current CPU, the lbr_select is not reset, which causes the previous lbr_select value to be visible to the next vcpu.
Considering that the requested lbr_select will be reconfigured when the event is enabled. It is trivial, but a valid fix. Thanks.
> > Cc: Like Xu <likexu@tencent.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > arch/x86/events/intel/lbr.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c > index 9e6d6eaeb4cb..1076de93a2f5 100644 > --- a/arch/x86/events/intel/lbr.c > +++ b/arch/x86/events/intel/lbr.c > @@ -279,6 +279,8 @@ void intel_pmu_lbr_reset(void) > > cpuc->last_task_ctx = NULL; > cpuc->last_log_id = 0; > + if (!static_cpu_has(X86_FEATURE_ARCH_LBR) && cpuc->lbr_select) > + wrmsrl(MSR_LBR_SELECT, 0); > } > > /* >
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