[PATCH 6.19 069/781] perf/x86/core: Do not set bit width for unavailable counters

Greg Kroah-Hartman
2026-02-25T01:28:55Z

From: Sandipan Das <sandipan.das@amd.com>

[ Upstream commit b456a6ba5756b6fb7e651775343e713bd08418e7 ]

Not all x86 processors have fixed counters. It may also be the case that
a processor has only fixed counters and no general-purpose counters. Set
the bit widths corresponding to each counter type only if such counters
are available.

Fixes: b3d9468a8bd2 ("perf, x86: Expose perf capability to other modules")
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Co-developed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Xudong Hao <xudong.hao@intel.com>
Link: https://patch.msgid.link/20251206001720.468579-11-seanjc@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/events/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 576baa9a52c5b..af1329ae9f82a 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -3073,8 +3073,8 @@ void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
cap->version = x86_pmu.version;
cap->num_counters_gp = x86_pmu_num_counters(NULL);
cap->num_counters_fixed = x86_pmu_num_counters_fixed(NULL);
- cap->bit_width_gp = x86_pmu.cntval_bits;
- cap->bit_width_fixed = x86_pmu.cntval_bits;
+ cap->bit_width_gp = cap->num_counters_gp ? x86_pmu.cntval_bits : 0;
+ cap->bit_width_fixed = cap->num_counters_fixed ? x86_pmu.cntval_bits : 0;
cap->events_mask = (unsigned int)x86_pmu.events_maskl;
cap->events_mask_len = x86_pmu.events_mask_len;
cap->pebs_ept = x86_pmu.pebs_ept;
--
2.51.0