linux-kernel - [PATCH 5/9] x86, perf: Add support for LBRv5

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Date:	Sun, 10 May 2015 12:22:43 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	peterz@...radead.org
Cc:	eranian@...gle.com, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 5/9] x86, perf: Add support for LBRv5

From: Andi Kleen <ak@...ux.intel.com>

Add support for the new LBRv5 format used on Skylake.

The flags for mispredict, abort, in_tx etc. moved to range of separate
LBR_INFO_* MSRs. Teach the LBR code to read those. The original
LBR registers stay the same, except they have full sign
extension now.

LBR_INFO also reports a cycle count to the last branch.
Report the cycle information using the new "cycles" branch_info
output field.

In addition we have to context switch and clear the new INFO
MSRs to avoid any information leaks.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/kernel/cpu/perf_event.h           |  1 +
 arch/x86/kernel/cpu/perf_event_intel_lbr.c | 21 ++++++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index c2031cb..6dabfdc 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -595,6 +595,7 @@ struct x86_pmu {
 struct x86_perf_task_context {
 	u64 lbr_from[MAX_LBR_ENTRIES];
 	u64 lbr_to[MAX_LBR_ENTRIES];
+	u64 lbr_info[MAX_LBR_ENTRIES];
 	int lbr_callstack_users;
 	int lbr_stack_state;
 };
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 94e5b50..d938cae 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -13,7 +13,8 @@ enum {
 	LBR_FORMAT_EIP		= 0x02,
 	LBR_FORMAT_EIP_FLAGS	= 0x03,
 	LBR_FORMAT_EIP_FLAGS2	= 0x04,
-	LBR_FORMAT_MAX_KNOWN    = LBR_FORMAT_EIP_FLAGS2,
+	LBR_FORMAT_INFO		= 0x05,
+	LBR_FORMAT_MAX_KNOWN    = LBR_FORMAT_INFO,
 };
 
 static enum {
@@ -184,6 +185,8 @@ static void intel_pmu_lbr_reset_64(void)
 	for (i = 0; i < x86_pmu.lbr_nr; i++) {
 		wrmsrl(x86_pmu.lbr_from + i, 0);
 		wrmsrl(x86_pmu.lbr_to   + i, 0);
+		if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
+			wrmsrl(MSR_LBR_INFO_0 + i, 0);
 	}
 }
 
@@ -232,6 +235,8 @@ static void __intel_pmu_lbr_restore(struct x86_perf_task_context *task_ctx)
 		lbr_idx = (tos - i) & mask;
 		wrmsrl(x86_pmu.lbr_from + lbr_idx, task_ctx->lbr_from[i]);
 		wrmsrl(x86_pmu.lbr_to + lbr_idx, task_ctx->lbr_to[i]);
+		if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
+			wrmsrl(MSR_LBR_INFO_0 + i, task_ctx->lbr_info[i]);
 	}
 	task_ctx->lbr_stack_state = LBR_NONE;
 }
@@ -253,6 +258,8 @@ static void __intel_pmu_lbr_save(struct x86_perf_task_context *task_ctx)
 		lbr_idx = (tos - i) & mask;
 		rdmsrl(x86_pmu.lbr_from + lbr_idx, task_ctx->lbr_from[i]);
 		rdmsrl(x86_pmu.lbr_to + lbr_idx, task_ctx->lbr_to[i]);
+		if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
+			rdmsrl(MSR_LBR_INFO_0 + i, task_ctx->lbr_info[i]);
 	}
 	task_ctx->lbr_stack_state = LBR_VALID;
 }
@@ -417,11 +424,22 @@ static void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
 		unsigned long lbr_idx = (tos - i) & mask;
 		u64 from, to, mis = 0, pred = 0, in_tx = 0, abort = 0;
 		int skip = 0;
+		u16 cycles = 0;
 		int lbr_flags = lbr_desc[lbr_format];
 
 		rdmsrl(x86_pmu.lbr_from + lbr_idx, from);
 		rdmsrl(x86_pmu.lbr_to   + lbr_idx, to);
 
+		if (lbr_format == LBR_FORMAT_INFO) {
+			u64 info;
+
+			rdmsrl(MSR_LBR_INFO_0 + lbr_idx, info);
+			mis = !!(info & LBR_INFO_MISPRED);
+			pred = !mis;
+			in_tx = !!(info & LBR_INFO_IN_TX);
+			abort = !!(info & LBR_INFO_ABORT);
+			cycles = (info & LBR_INFO_CYCLES);
+		}
 		if (lbr_flags & LBR_EIP_FLAGS) {
 			mis = !!(from & LBR_FROM_FLAG_MISPRED);
 			pred = !mis;
@@ -451,6 +469,7 @@ static void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
 		cpuc->lbr_entries[out].predicted = pred;
 		cpuc->lbr_entries[out].in_tx	 = in_tx;
 		cpuc->lbr_entries[out].abort	 = abort;
+		cpuc->lbr_entries[out].cycles	 = cycles;
 		cpuc->lbr_entries[out].reserved	 = 0;
 		out++;
 	}
-- 
1.9.3

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