From a91f86e27087f250a5d9c89bb4a427b9c30fd815 Mon Sep 17 00:00:00 2001 From: Lisa Robinson Date: Sat, 17 Jan 2026 10:56:43 +0800 Subject: [PATCH] LoongArch: Fix PMU counter allocation for mixed-type event groups When validating a perf event group, validate_group() unconditionally attempts to allocate hardware PMU counters for the leader, sibling events and the new event being added. This is incorrect for mixed-type groups. If a PERF_TYPE_SOFTWARE event is part of the group, the current code still tries to allocate a hardware PMU counter for it, which can wrongly consume hardware PMU resources and cause spurious allocation failures. Fix this by only allocating PMU counters for hardware events during group validation, and skipping software events. A trimmed down reproducer is as simple as this: #include #include #include #include #include #include int main (int argc, char *argv[]) { struct perf_event_attr attr = { 0 }; int fds[5]; attr.disabled = 1; attr.exclude_kernel = 1; attr.exclude_hv = 1; attr.read_format = PERF_FORMAT_TOTAL_TIME_ENABLED | PERF_FORMAT_TOTAL_TIME_RUNNING | PERF_FORMAT_ID | PERF_FORMAT_GROUP; attr.size = sizeof (attr); attr.type = PERF_TYPE_SOFTWARE; attr.config = PERF_COUNT_SW_DUMMY; fds[0] = syscall (SYS_perf_event_open, &attr, 0, -1, -1, 0); assert (fds[0] >= 0); attr.type = PERF_TYPE_HARDWARE; attr.config = PERF_COUNT_HW_CPU_CYCLES; fds[1] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0); assert (fds[1] >= 0); attr.type = PERF_TYPE_HARDWARE; attr.config = PERF_COUNT_HW_INSTRUCTIONS; fds[2] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0); assert (fds[2] >= 0); attr.type = PERF_TYPE_HARDWARE; attr.config = PERF_COUNT_HW_BRANCH_MISSES; fds[3] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0); assert (fds[3] >= 0); attr.type = PERF_TYPE_HARDWARE; attr.config = PERF_COUNT_HW_CACHE_REFERENCES; fds[4] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0); assert (fds[4] >= 0); printf ("PASSED\n"); return 0; } Cc: stable@vger.kernel.org Fixes: b37042b2bb7c ("LoongArch: Add perf events support") Signed-off-by: Lisa Robinson Signed-off-by: Huacai Chen --- arch/loongarch/kernel/perf_event.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/arch/loongarch/kernel/perf_event.c b/arch/loongarch/kernel/perf_event.c index 9d257c8519c9..e34a6fb33e11 100644 --- a/arch/loongarch/kernel/perf_event.c +++ b/arch/loongarch/kernel/perf_event.c @@ -626,6 +626,18 @@ static const struct loongarch_perf_event *loongarch_pmu_map_cache_event(u64 conf return pev; } +static inline bool loongarch_pmu_event_requires_counter(const struct perf_event *event) +{ + switch (event->attr.type) { + case PERF_TYPE_HARDWARE: + case PERF_TYPE_HW_CACHE: + case PERF_TYPE_RAW: + return true; + default: + return false; + } +} + static int validate_group(struct perf_event *event) { struct cpu_hw_events fake_cpuc; @@ -633,15 +645,18 @@ static int validate_group(struct perf_event *event) memset(&fake_cpuc, 0, sizeof(fake_cpuc)); - if (loongarch_pmu_alloc_counter(&fake_cpuc, &leader->hw) < 0) + if (loongarch_pmu_event_requires_counter(leader) && + loongarch_pmu_alloc_counter(&fake_cpuc, &leader->hw) < 0) return -EINVAL; for_each_sibling_event(sibling, leader) { - if (loongarch_pmu_alloc_counter(&fake_cpuc, &sibling->hw) < 0) + if (loongarch_pmu_event_requires_counter(sibling) && + loongarch_pmu_alloc_counter(&fake_cpuc, &sibling->hw) < 0) return -EINVAL; } - if (loongarch_pmu_alloc_counter(&fake_cpuc, &event->hw) < 0) + if (loongarch_pmu_event_requires_counter(event) && + loongarch_pmu_alloc_counter(&fake_cpuc, &event->hw) < 0) return -EINVAL; return 0; -- 2.47.3