From a6b5fbc33172509fbe991358d718617a8e33ea7e Mon Sep 17 00:00:00 2001 From: Dapeng Mi Date: Tue, 16 Jun 2026 12:46:52 +0800 Subject: [PATCH] perf/x86/intel: Drop fixed-counter PEBS constraints for baseline PEBS On Sapphire Rapids (SPR) guests where pebs_baseline is not advertised, running command $ ./perf record -e cpu/event=0x00,umask=0x01,i\ name=INST_RETIRED.PREC_DIST/p -c 10000 sleep 1 can trigger: unchecked MSR access error: WRMSR to 0x3f1 ... in\ intel_pmu_pebs_enable_all() This occurs because SPR-specific PEBS constraints allow fixed-counter scheduling (for example, INST_RETIRED.PREC_DIST on fixed counter 0). In guests lacking pebs_baseline, KVM does not support PEBS sampling on fixed counters, so enabling such events reaches an invalid MSR programming path. Starting with Icelake, regardless of whether Extended PEBS or Architectural PEBS is in use, all counters (including fixed counters) support PEBS sampling, and the PMU_FL_PEBS_ALL flag is set by default. As long as PMU_FL_PEBS_ALL is set, constraint lookup automatically falls back to the corresponding non-PEBS constraints if no matching entry is found in the PEBS constraints table. Since non-PEBS event constraints already contain the same fixed-counter constraints, it is safe to remove these fixed-counter entries from the PEBS constraints table. The fallback mechanism will ensure that fixed PEBS events are scheduled onto the correct fixed counters. So, directly drop the fixed-counter entries from the PEBS constraint table. Without pebs_baseline, these fixed-counter PEBS events will now resolve to empty constraints and will not be scheduled or enabled, thereby avoiding the warning and bypassing the broken guest PEBS path. Reported-by: Yi Lai Signed-off-by: Dapeng Mi Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260616044654.3468742-7-dapeng1.mi@linux.intel.com --- arch/x86/events/intel/ds.c | 13 ------------- 1 file changed, 13 deletions(-) diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index 91a093d8cf2e..e86e4ba91e1b 100644 --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -1444,10 +1444,6 @@ struct event_constraint intel_skl_pebs_event_constraints[] = { }; struct event_constraint intel_icl_pebs_event_constraints[] = { - INTEL_FLAGS_UEVENT_CONSTRAINT(0x01c0, 0x100000000ULL), /* old INST_RETIRED.PREC_DIST */ - INTEL_FLAGS_UEVENT_CONSTRAINT(0x0100, 0x100000000ULL), /* INST_RETIRED.PREC_DIST */ - INTEL_FLAGS_UEVENT_CONSTRAINT(0x0400, 0x800000000ULL), /* SLOTS */ - INTEL_PLD_CONSTRAINT(0x1cd, 0xff), /* MEM_TRANS_RETIRED.LOAD_LATENCY */ INTEL_FLAGS_UEVENT_CONSTRAINT_DATALA_LD(0x11d0, 0xf), /* MEM_INST_RETIRED.STLB_MISS_LOADS */ INTEL_FLAGS_UEVENT_CONSTRAINT_DATALA_ST(0x12d0, 0xf), /* MEM_INST_RETIRED.STLB_MISS_STORES */ @@ -1470,9 +1466,6 @@ struct event_constraint intel_icl_pebs_event_constraints[] = { }; struct event_constraint intel_glc_pebs_event_constraints[] = { - INTEL_FLAGS_UEVENT_CONSTRAINT(0x100, 0x100000000ULL), /* INST_RETIRED.PREC_DIST */ - INTEL_FLAGS_UEVENT_CONSTRAINT(0x0400, 0x800000000ULL), - INTEL_FLAGS_EVENT_CONSTRAINT(0xc0, 0xfe), INTEL_PLD_CONSTRAINT(0x1cd, 0xfe), INTEL_PSD_CONSTRAINT(0x2cd, 0x1), @@ -1497,9 +1490,6 @@ struct event_constraint intel_glc_pebs_event_constraints[] = { }; struct event_constraint intel_lnc_pebs_event_constraints[] = { - INTEL_FLAGS_UEVENT_CONSTRAINT(0x100, 0x100000000ULL), /* INST_RETIRED.PREC_DIST */ - INTEL_FLAGS_UEVENT_CONSTRAINT(0x0400, 0x800000000ULL), - INTEL_FLAGS_UEVENT_CONSTRAINT(0x012a, 0x1), /* OCR.* events */ INTEL_FLAGS_UEVENT_CONSTRAINT(0x012b, 0x1), /* OCR.* events */ @@ -1531,9 +1521,6 @@ struct event_constraint intel_lnc_pebs_event_constraints[] = { }; struct event_constraint intel_pnc_pebs_event_constraints[] = { - INTEL_FLAGS_UEVENT_CONSTRAINT(0x100, 0x100000000ULL), /* INST_RETIRED.PREC_DIST */ - INTEL_FLAGS_UEVENT_CONSTRAINT(0x0400, 0x800000000ULL), - INTEL_HYBRID_LDLAT_CONSTRAINT(0x1cd, 0xfc), INTEL_HYBRID_STLAT_CONSTRAINT(0x2cd, 0x3), INTEL_FLAGS_UEVENT_CONSTRAINT_DATALA_LD(0x11d0, 0xf), /* MEM_INST_RETIRED.STLB_MISS_LOADS */