perf/x86/intel/lbr: Add support for LBRv5

Andi Kleen · Ingo Molnar · commit 50eab8f6ecd7 · 2015-08-04T10:16:57.000+02:00
Add support for the new LBRv5 format used on Intel Skylake CPUs. 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@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: eranian@google.com Link: http://lkml.kernel.org/r/1431285767-27027-6-git-send-email-andi@firstfloor.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
@@ -625,6 +625,7 @@ 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
@@ -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 {
@@ -186,6 +187,8 @@ 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);
 	}
 }
 
@@ -234,6 +237,8 @@ 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;
 }
@@ -255,6 +260,8 @@ 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;
 }
@@ -416,11 +423,22 @@ 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;
@@ -450,6 +468,7 @@ 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++;
 	}
