From 5ad732a56be46aabf158c16aa0c095291727aaef Mon Sep 17 00:00:00 2001 From: Dapeng Mi Date: Thu, 30 Apr 2026 08:25:54 +0800 Subject: [PATCH] perf/x86/intel: Improve validation and configuration of ACR masks Currently there are several issues on the user space ACR mask validation and configuration. - The validation for user space ACR mask (attr.config2) is incomplete, e.g., the ACR mask could include the index which belongs to another ACR events group, but it's not validated. - An early return on an invalid ACR mask caused all subsequent ACR groups to be skipped. - The stale hardware ACR mask (hw.config1) is not cleared before setting new hardware ACR mask. The following changes address all of the above issues. - Figure out the event index group of an ACR group. Any bits in the user-space mask not present in the index group are now dropped. - Instead of an early return on invalid bits, drop only the invalid portions and continue iterating through all ACR events to ensure full configuration. - Explicitly clear the stale hardware ACR mask for each event prior to writing the new configuration. Besides, a non-leader event member of ACR group could be disabled in theory. This could cause bit-shifting errors in the acr_mask of remaining group members. But since ACR sampling requires all events to be active, this should not be a big concern in real use case. Add a "FIXME" comment to notice this risk. Fixes: ec980e4facef ("perf/x86/intel: Support auto counter reload") Signed-off-by: Dapeng Mi Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260430002558.712334-2-dapeng1.mi@linux.intel.com --- arch/x86/events/intel/core.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index d9488ade0f8e..f8deb67b3c51 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3332,23 +3332,41 @@ static void intel_pmu_enable_event(struct perf_event *event) static void intel_pmu_acr_late_setup(struct cpu_hw_events *cpuc) { struct perf_event *event, *leader; - int i, j, idx; + int i, j, k, bit, idx; + /* + * FIXME: ACR mask parsing relies on cpuc->event_list[] (active events only). + * Disabling an ACR event causes bit-shifting errors in the acr_mask of + * remaining group members. As ACR sampling requires all events to be active, + * this limitation is acceptable for now. Revisit if independent event toggling + * is required. + */ for (i = 0; i < cpuc->n_events; i++) { leader = cpuc->event_list[i]; if (!is_acr_event_group(leader)) continue; - /* The ACR events must be contiguous. */ + /* Find the last event of the ACR group. */ for (j = i; j < cpuc->n_events; j++) { event = cpuc->event_list[j]; if (event->group_leader != leader->group_leader) break; - for_each_set_bit(idx, (unsigned long *)&event->attr.config2, X86_PMC_IDX_MAX) { - if (i + idx >= cpuc->n_events || - !is_acr_event_group(cpuc->event_list[i + idx])) - return; - __set_bit(cpuc->assign[i + idx], (unsigned long *)&event->hw.config1); + } + + /* + * Translate the user-space ACR mask (attr.config2) into the physical + * counter bitmask (hw.config1) for each ACR event in the group. + * NOTE: ACR event contiguity is guaranteed by intel_pmu_hw_config(). + */ + for (k = i; k < j; k++) { + event = cpuc->event_list[k]; + event->hw.config1 = 0; + for_each_set_bit(bit, (unsigned long *)&event->attr.config2, X86_PMC_IDX_MAX) { + idx = i + bit; + /* Event index of ACR group must locate in [i, j). */ + if (idx >= j || !is_acr_event_group(cpuc->event_list[idx])) + continue; + __set_bit(cpuc->assign[idx], (unsigned long *)&event->hw.config1); } } i = j - 1;