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Subject[PATCH v8 02/14] perf/x86: add a function to get the addresses of the lbr stack msrs
Date
The lbr stack msrs are model specific. The perf subsystem has already
assigned the abstracted msr address values based on the cpu model.
So add a function to enable callers outside the perf subsystem to get the
lbr stack addresses. This is useful for hypervisors to emulate the lbr
feature for the guest.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
---
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 6f814a2..9b2d05c 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1311,3 +1311,26 @@ 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;
}
+
+/**
+ * x86_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 x86_perf_get_lbr_stack(struct x86_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(x86_perf_get_lbr_stack);
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 1392d5e..2606100 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -318,7 +318,16 @@ struct perf_guest_switch_msr {
u64 host, guest;
};

+struct x86_perf_lbr_stack {
+ unsigned int nr;
+ unsigned int tos;
+ unsigned int from;
+ unsigned int to;
+ unsigned int info;
+};
+
extern struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr);
+extern int x86_perf_get_lbr_stack(struct x86_perf_lbr_stack *stack);
extern void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap);
extern void perf_check_microcode(void);
extern int x86_perf_rdpmc_index(struct perf_event *event);
@@ -329,6 +338,11 @@ static inline struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr)
return NULL;
}

+static inline int x86_perf_get_lbr_stack(struct x86_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
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