linux-kernel - [PATCH v6 02/12] perf/x86: add a function to get the lbr stack

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Date:   Thu,  6 Jun 2019 15:02:21 +0800
From:   Wei Wang <wei.w.wang@...el.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pbonzini@...hat.com, ak@...ux.intel.com, peterz@...radead.org
Cc:     kan.liang@...el.com, mingo@...hat.com, rkrcmar@...hat.com,
        like.xu@...el.com, wei.w.wang@...el.com, jannh@...gle.com,
        arei.gonglei@...wei.com, jmattson@...gle.com
Subject: [PATCH v6 02/12] perf/x86: add a function to get the lbr stack

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: Wei Wang <wei.w.wang@...el.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 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..784642a 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