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SubjectRe: [RFC PATCH v2 2/3] perf/x86/intel/pt: Introduce and export pt_get_curr_event()
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On 9/22/2022 12:45 AM, Xiaoyao Li wrote:
> KVM supports PT_MODE_HOST_GUEST mode for Intel PT where host and guest
> have separate Intel PT configurations and they work independently.
>
> Currently, in this mode, when both host and guest enable PT, KVM manually
> clears MSR_IA32_RTIT_CTL.TRACEEN to disable host PT so that it can
> context switch the other PT MSRs. However, PT PMI can be delivered after
> this point and before the VM-entry. As a result, the re-enabling of PT
> leads to VM-entry failure of guest.
>
> To solve the problem, introduce and export pt_get_curr_event() for KVM
> to get current pt event. Along with perf_event_{dis, en}able_local(),
> With them, KVM can avoid PT re-enabling in PT PMI handler.
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
> arch/x86/events/intel/pt.c | 8 ++++++++
> arch/x86/include/asm/perf_event.h | 2 ++
> 2 files changed, 10 insertions(+)
>
> diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
> index 82ef87e9a897..62bfc45c11c9 100644
> --- a/arch/x86/events/intel/pt.c
> +++ b/arch/x86/events/intel/pt.c
> @@ -1624,6 +1624,14 @@ static void pt_event_stop(struct perf_event *event, int mode)
> }
> }
>
> +struct perf_event *pt_get_curr_event(void)
> +{
> + struct pt *pt = this_cpu_ptr(&pt_ctx);
> +
> + return pt->handle.event;
> +}
> +EXPORT_SYMBOL_GPL(pt_get_curr_event);
> +
> static long pt_event_snapshot_aux(struct perf_event *event,
> struct perf_output_handle *handle,
> unsigned long size)
> diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
> index f6fc8dd51ef4..7c3533392cf5 100644
> --- a/arch/x86/include/asm/perf_event.h
> +++ b/arch/x86/include/asm/perf_event.h
> @@ -553,11 +553,13 @@ static inline int x86_perf_get_lbr(struct x86_pmu_lbr *lbr)
>
> #ifdef CONFIG_CPU_SUP_INTEL
> extern void intel_pt_handle_vmx(int on);
> + extern struct perf_event *pt_get_curr_event(void);
> #else
> static inline void intel_pt_handle_vmx(int on)
> {
>
> }
> +struct perf_event *pt_get_curr_event(void) { return NULL; }

My fault, this needs to be

static inline ...

> #endif
>
> #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_AMD)

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