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Message-ID: <aC4vyIpKk6m2nz8-@google.com>
Date: Wed, 21 May 2025 12:55:52 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Mingwei Zhang <mizhang@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>, Liang@...gle.com,
Kan <kan.liang@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
Yongwei Ma <yongwei.ma@...el.com>,
Xiong Zhang <xiong.y.zhang@...ux.intel.com>,
Dapeng Mi <dapeng1.mi@...ux.intel.com>,
Jim Mattson <jmattson@...gle.com>,
Sandipan Das <sandipan.das@....com>,
Zide Chen <zide.chen@...el.com>,
Eranian Stephane <eranian@...gle.com>,
Shukla Manali <Manali.Shukla@....com>,
Nikunj Dadhania <nikunj.dadhania@....com>
Subject: Re: [PATCH v4 05/38] perf: Add generic exclude_guest support
On Mon, Mar 24, 2025 at 05:30:45PM +0000, Mingwei Zhang wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
>
> Only KVM knows the exact time when a guest is entering/exiting. Expose
> two interfaces to KVM to switch the ownership of the PMU resources.
>
> All the pinned events must be scheduled in first. Extend the
> perf_event_sched_in() helper to support extra flag, e.g., EVENT_GUEST.
>
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
> ---
> include/linux/perf_event.h | 4 ++
> kernel/events/core.c | 80 ++++++++++++++++++++++++++++++++++----
> 2 files changed, 77 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 7bda1e20be12..37187ee8e226 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1822,6 +1822,8 @@ extern int perf_event_period(struct perf_event *event, u64 value);
> extern u64 perf_event_pause(struct perf_event *event, bool reset);
> int perf_get_mediated_pmu(void);
> void perf_put_mediated_pmu(void);
> +void perf_guest_enter(void);
> +void perf_guest_exit(void);
> #else /* !CONFIG_PERF_EVENTS: */
> static inline void *
> perf_aux_output_begin(struct perf_output_handle *handle,
> @@ -1919,6 +1921,8 @@ static inline int perf_get_mediated_pmu(void)
> }
>
> static inline void perf_put_mediated_pmu(void) { }
> +static inline void perf_guest_enter(void) { }
> +static inline void perf_guest_exit(void) { }
> #endif
>
> #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 7a2115b2c5c1..d05487d465c9 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -2827,14 +2827,15 @@ static void task_ctx_sched_out(struct perf_event_context *ctx,
>
> static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
> struct perf_event_context *ctx,
> - struct pmu *pmu)
> + struct pmu *pmu,
> + enum event_type_t event_type)
> {
> - ctx_sched_in(&cpuctx->ctx, pmu, EVENT_PINNED);
> + ctx_sched_in(&cpuctx->ctx, pmu, EVENT_PINNED | event_type);
> if (ctx)
> - ctx_sched_in(ctx, pmu, EVENT_PINNED);
> - ctx_sched_in(&cpuctx->ctx, pmu, EVENT_FLEXIBLE);
> + ctx_sched_in(ctx, pmu, EVENT_PINNED | event_type);
> + ctx_sched_in(&cpuctx->ctx, pmu, EVENT_FLEXIBLE | event_type);
> if (ctx)
> - ctx_sched_in(ctx, pmu, EVENT_FLEXIBLE);
> + ctx_sched_in(ctx, pmu, EVENT_FLEXIBLE | event_type);
> }
>
> /*
> @@ -2890,7 +2891,7 @@ static void ctx_resched(struct perf_cpu_context *cpuctx,
> else if (event_type & EVENT_PINNED)
> ctx_sched_out(&cpuctx->ctx, pmu, EVENT_FLEXIBLE);
>
> - perf_event_sched_in(cpuctx, task_ctx, pmu);
> + perf_event_sched_in(cpuctx, task_ctx, pmu, 0);
>
> for_each_epc(epc, &cpuctx->ctx, pmu, 0)
> perf_pmu_enable(epc->pmu);
> @@ -4188,7 +4189,7 @@ static void perf_event_context_sched_in(struct task_struct *task)
> ctx_sched_out(&cpuctx->ctx, NULL, EVENT_FLEXIBLE);
> }
>
> - perf_event_sched_in(cpuctx, ctx, NULL);
> + perf_event_sched_in(cpuctx, ctx, NULL, 0);
>
> perf_ctx_sched_task_cb(cpuctx->task_ctx, true);
>
> @@ -6040,6 +6041,71 @@ void perf_put_mediated_pmu(void)
> }
> EXPORT_SYMBOL_GPL(perf_put_mediated_pmu);
>
> +static inline void perf_host_exit(struct perf_cpu_context *cpuctx)
> +{
> + perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST);
> + ctx_sched_out(&cpuctx->ctx, NULL, EVENT_GUEST);
> + perf_ctx_enable(&cpuctx->ctx, EVENT_GUEST);
> + if (cpuctx->task_ctx) {
> + perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST);
> + task_ctx_sched_out(cpuctx->task_ctx, NULL, EVENT_GUEST);
> + perf_ctx_enable(cpuctx->task_ctx, EVENT_GUEST);
> + }
> +}
Cpu context and task context may have events in the same PMU.
How about this?
perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST);
if (cpuctx->task_ctx)
perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST);
ctx_sched_out(&cpuctx->ctx, NULL, EVENT_GUEST);
if (cpuctx->task_ctx)
task_ctx_sched_out(cpuctx->task_ctx, NULL, EVENT_GUEST);
if (cpuctx->task_ctx)
perf_ctx_enable(cpuctx->task_ctx, EVENT_GUEST);
perf_ctx_enable(&cpuctx->ctx, EVENT_GUEST);
Thanks,
Namhyung
> +
> +/* When entering a guest, schedule out all exclude_guest events. */
> +void perf_guest_enter(void)
> +{
> + struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
> +
> + lockdep_assert_irqs_disabled();
> +
> + perf_ctx_lock(cpuctx, cpuctx->task_ctx);
> +
> + if (WARN_ON_ONCE(__this_cpu_read(perf_in_guest)))
> + goto unlock;
> +
> + perf_host_exit(cpuctx);
> +
> + __this_cpu_write(perf_in_guest, true);
> +
> +unlock:
> + perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
> +}
> +EXPORT_SYMBOL_GPL(perf_guest_enter);
> +
> +static inline void perf_host_enter(struct perf_cpu_context *cpuctx)
> +{
> + perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST);
> + if (cpuctx->task_ctx)
> + perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST);
> +
> + perf_event_sched_in(cpuctx, cpuctx->task_ctx, NULL, EVENT_GUEST);
> +
> + if (cpuctx->task_ctx)
> + perf_ctx_enable(cpuctx->task_ctx, EVENT_GUEST);
> + perf_ctx_enable(&cpuctx->ctx, EVENT_GUEST);
> +}
> +
> +void perf_guest_exit(void)
> +{
> + struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
> +
> + lockdep_assert_irqs_disabled();
> +
> + perf_ctx_lock(cpuctx, cpuctx->task_ctx);
> +
> + if (WARN_ON_ONCE(!__this_cpu_read(perf_in_guest)))
> + goto unlock;
> +
> + perf_host_enter(cpuctx);
> +
> + __this_cpu_write(perf_in_guest, false);
> +unlock:
> + perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
> +}
> +EXPORT_SYMBOL_GPL(perf_guest_exit);
> +
> /*
> * Holding the top-level event's child_mutex means that any
> * descendant process that has inherited this event will block
> --
> 2.49.0.395.g12beb8f557-goog
>
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