The LBR stack MSRs are architecturally specific. The perf subsystem has
already assigned the abstracted MSR values based on the CPU architecture.
This patch enables a caller outside the perf subsystem to get the LBR
stack info. This is useful for hyperviosrs to prepare the lbr feature
for the guest.
Signed-off-by: Like Xu <like.xu@xxxxxxxxx>
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
arch/x86/events/intel/lbr.c | 23 +++++++++++++++++++++++
arch/x86/include/asm/perf_event.h | 14 ++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index c88ed39..c81f160 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1277,3 +1277,26 @@ void intel_pmu_lbr_init_knl(void)
if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_LIP)
x86_pmu.intel_cap.lbr_format = LBR_FORMAT_EIP_FLAGS;
}
+
+/**
+ * perf_get_lbr_stack - get the lbr stack related MSRs
+ *
+ * @stack: the caller's memory to get the lbr stack
+ *
+ * Returns: 0 indicates that the lbr stack has been successfully obtained.
+ */
+int perf_get_lbr_stack(struct perf_lbr_stack *stack)
+{
+ stack->nr = x86_pmu.lbr_nr;
+ stack->tos = x86_pmu.lbr_tos;
+ stack->from = x86_pmu.lbr_from;
+ stack->to = x86_pmu.lbr_to;
+
+ if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
+ stack->info = MSR_LBR_INFO_0;
+ else
+ stack->info = 0;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(perf_get_lbr_stack);
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 12f5408..84cc8cb 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -267,7 +267,16 @@ struct perf_guest_switch_msr {
u64 host, guest;
};
+struct perf_lbr_stack {
+ int nr;
+ unsigned long tos;
+ unsigned long from;
+ unsigned long to;
+ unsigned long info;
+};
+
extern struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr);
+extern int perf_get_lbr_stack(struct perf_lbr_stack *stack);
extern void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap);
extern void perf_check_microcode(void);
#else
@@ -277,6 +286,11 @@ static inline struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr)
return NULL;
}
+static inline int perf_get_lbr_stack(struct perf_lbr_stack *stack)
+{
+ return -1;
+}
+
static inline void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
{
memset(cap, 0, sizeof(*cap));
--
2.7.4
