From 3c4ec9b2a5db56b60127bfaf933ecdeea7a1f10a Mon Sep 17 00:00:00 2001 From: Dapeng Mi Date: Tue, 16 Jun 2026 12:46:48 +0800 Subject: [PATCH] perf/x86/intel: Keep cap_user_rdpmc in sync with RDPMC user-disable state After introducing the RDPMC user disable feature, user-space RDPMC may return 0 instead of the actual event count. This creates an inconsistency with cap_user_rdpmc, where cap_user_rdpmc is set, but user-space RDPMC only returns 0. To accurately represent the user-space RDPMC capability, update cap_user_rdpmc (depending on PERF_EVENT_FLAG_USER_READ_CNT) according to the RDPMC user disable state. If RDPMC user disable is enabled, cap_user_rdpmc is updated to false eventually, allowing user-space programs to fall back to the read() syscall to obtain the real event count. Because PERF_EVENT_FLAG_USER_READ_CNT is evaluated in x86_pmu_event_init(), move intel_pmu_update_rdpmc_user_disable() earlier into intel_pmu_hw_config(). This ensures that the user-disable state is updated before updating PERF_EVENT_FLAG_USER_READ_CNT. Note that since event->ctx is not yet assigned at this stage, use the PERF_ATTACH_TASK flag to detect whether the event is task-attached. While at it, fix the indentation of x86_pmu_has_rdpmc_user_disable() to adhere to the kernel coding style. Fixes: 59af95e028d4 ("perf/x86/intel: Add support for rdpmc user disable feature") Signed-off-by: Dapeng Mi Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260616044654.3468742-3-dapeng1.mi@linux.intel.com --- arch/x86/events/core.c | 3 ++- arch/x86/events/intel/core.c | 6 +++--- arch/x86/events/perf_event.h | 2 +- 3 files changed, 6 insertions(+), 5 deletions(-) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index d1af33d96d0a..af0b67ffb43d 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2539,7 +2539,8 @@ static int x86_pmu_event_init(struct perf_event *event) } if (READ_ONCE(x86_pmu.attr_rdpmc) && - !(event->hw.flags & PERF_X86_EVENT_LARGE_PEBS)) + !(event->hw.flags & PERF_X86_EVENT_LARGE_PEBS) && + !(event->hw.config & ARCH_PERFMON_EVENTSEL_RDPMC_USER_DISABLE)) event->hw.flags |= PERF_EVENT_FLAG_USER_READ_CNT; return err; diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 465c414f145d..5116b15438a2 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3533,7 +3533,7 @@ static void intel_pmu_update_rdpmc_user_disable(struct perf_event *event) */ if (x86_pmu.attr_rdpmc == X86_USER_RDPMC_ALWAYS_ENABLE || (x86_pmu.attr_rdpmc == X86_USER_RDPMC_CONDITIONAL_ENABLE && - event->ctx->task)) + (event->attach_state & PERF_ATTACH_TASK))) event->hw.config &= ~ARCH_PERFMON_EVENTSEL_RDPMC_USER_DISABLE; else event->hw.config |= ARCH_PERFMON_EVENTSEL_RDPMC_USER_DISABLE; @@ -3547,8 +3547,6 @@ static void intel_pmu_enable_event(struct perf_event *event) struct hw_perf_event *hwc = &event->hw; int idx = hwc->idx; - intel_pmu_update_rdpmc_user_disable(event); - if (unlikely(event->attr.precise_ip)) static_call(x86_pmu_pebs_enable)(event); @@ -5147,6 +5145,8 @@ static int intel_pmu_hw_config(struct perf_event *event) leader->hw.flags |= PERF_X86_EVENT_ACR; } + intel_pmu_update_rdpmc_user_disable(event); + if ((event->attr.type == PERF_TYPE_HARDWARE) || (event->attr.type == PERF_TYPE_HW_CACHE)) return 0; diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h index 5902a297daa1..a8afea8d38f0 100644 --- a/arch/x86/events/perf_event.h +++ b/arch/x86/events/perf_event.h @@ -1344,7 +1344,7 @@ static inline u64 x86_pmu_get_event_config(struct perf_event *event) static inline bool x86_pmu_has_rdpmc_user_disable(struct pmu *pmu) { return !!(hybrid(pmu, config_mask) & - ARCH_PERFMON_EVENTSEL_RDPMC_USER_DISABLE); + ARCH_PERFMON_EVENTSEL_RDPMC_USER_DISABLE); } extern struct event_constraint emptyconstraint;