[PATCH 2/3] perf/x86/intel: Expose existence of callback support to KVM

Sean Christopherson
2024-03-07T01:13:51Z

Add a "has_callstack" field to the x86_pmu_lbr structure used to pass
information to KVM, and set it accordingly in x86_perf_get_lbr(). KVM
will use has_callstack to avoid trying to create perf LBR events with
PERF_SAMPLE_BRANCH_CALL_STACK on CPUs that don't support callstacks.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/events/intel/lbr.c | 1 +
arch/x86/include/asm/perf_event.h | 1 +
2 files changed, 2 insertions(+)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 78cd5084104e..4367aa77cb8d 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1693,6 +1693,7 @@ void x86_perf_get_lbr(struct x86_pmu_lbr *lbr)
lbr->from = x86_pmu.lbr_from;
lbr->to = x86_pmu.lbr_to;
lbr->info = x86_pmu.lbr_info;
+ lbr->has_callstack = x86_pmu_has_lbr_callstack();
}
EXPORT_SYMBOL_GPL(x86_perf_get_lbr);

diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 3736b8a46c04..7f1e17250546 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -555,6 +555,7 @@ struct x86_pmu_lbr {
unsigned int from;
unsigned int to;
unsigned int info;
+ bool has_callstack;
};

extern void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap);
--
2.44.0.278.ge034bb2e1d-goog