[tip: perf/core] perf/x86/intel: Fallback to sw branch type decoding if no hw decoding

[tip-bot2 for Dapeng Mi]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     170cc6b02e3d5203ccaa49ffea1ee5a7ab08c885
Gitweb:        https://git.kernel.org/tip/170cc6b02e3d5203ccaa49ffea1ee5a7ab08c885
Author:        Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
AuthorDate:    Tue, 16 Jun 2026 12:46:49 +08:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 30 Jun 2026 11:46:06 +02:00

perf/x86/intel: Fallback to sw branch type decoding if no hw decoding

intel_pmu_lbr_filter() currently assumes arch-LBR provides hardware
branch-type decoding and skips software decoding on that path.

However, arch-LBR may not always expose branch-type information. In
that case, treating entries as hardware-decoded can misclassify sampled
branches (for example, defaulting to JCC), which breaks branch-type
filtering results.

Fix this by using software branch-type decoding when hardware
branch-type decoding is unavailable (that is, when x86_lbr_type is not
enabled). This keeps branch classification and filtering behavior
correct across arch-LBR configurations.

Since x86_lbr_type is only set to true when arch-LBR is supported,
it's unnecessary to check if the CPU has the arch-LBR feature.

Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://patch.msgid.link/20260616044654.3468742-4-dapeng1.mi@xxxxxxxxxxxxxxx
---
 arch/x86/events/intel/lbr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index cae2e02..688d1df 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1232,7 +1232,7 @@ intel_pmu_lbr_filter(struct cpu_hw_events *cpuc)
 		 * Doesn't support OTHER_BRANCH decoding for now.
 		 * OTHER_BRANCH branch type still rely on software decoding.
 		 */
-		if (static_cpu_has(X86_FEATURE_ARCH_LBR) &&
+		if (static_branch_likely(&x86_lbr_type) &&
 		    type <= ARCH_LBR_BR_TYPE_KNOWN_MAX) {
 			to_plm = kernel_ip(to) ? X86_BR_KERNEL : X86_BR_USER;
 			type = arch_lbr_br_type_map[type] | to_plm;