perf: Enable branch record for software events
The typical way to access branch record (e.g. Intel LBR) is via hardware
perf_event. For CPUs with FREEZE_LBRS_ON_PMI support, PMI could capture
reliable LBR. On the other hand, LBR could also be useful in non-PMI
scenario. For example, in kretprobe or bpf fexit program, LBR could
provide a lot of information on what happened with the function. Add API
to use branch record for software use.
Note that, when the software event triggers, it is necessary to stop the
branch record hardware asap. Therefore, static_call is used to remove some
branch instructions in this process.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210910183352.3151445-2-songliubraving@fb.com
diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 9e6d6ea..6b72e9b 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -228,20 +228,6 @@ static void __intel_pmu_lbr_enable(bool pmi)
wrmsrl(MSR_ARCH_LBR_CTL, lbr_select | ARCH_LBR_CTL_LBREN);
}
-static void __intel_pmu_lbr_disable(void)
-{
- u64 debugctl;
-
- if (static_cpu_has(X86_FEATURE_ARCH_LBR)) {
- wrmsrl(MSR_ARCH_LBR_CTL, 0);
- return;
- }
-
- rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
- debugctl &= ~(DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
- wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
-}
-
void intel_pmu_lbr_reset_32(void)
{
int i;
@@ -779,8 +765,12 @@ void intel_pmu_lbr_disable_all(void)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
- if (cpuc->lbr_users && !vlbr_exclude_host())
+ if (cpuc->lbr_users && !vlbr_exclude_host()) {
+ if (static_cpu_has(X86_FEATURE_ARCH_LBR))
+ return __intel_pmu_arch_lbr_disable();
+
__intel_pmu_lbr_disable();
+ }
}
void intel_pmu_lbr_read_32(struct cpu_hw_events *cpuc)