From c77d142d2aa36857fb02bcef9bd6198e7e1b71c1 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Wed, 8 Dec 2010 15:56:23 +0100
Subject: [PATCH] --- yaml --- r: 223920 b: refs/heads/master c:
 4407204c5c9037763aadce39b025529dfbfcac9e h: refs/heads/master v: v3

---
 [refs]                                 |  2 +-
 trunk/arch/x86/kernel/cpu/perf_event.c | 48 ++++++++++++++++++++++----
 2 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/[refs] b/[refs]
index 30b71627529a..146ca4f61e3d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 006b20fe4c69189b0d854e5eabf269e50ca86cdd
+refs/heads/master: 4407204c5c9037763aadce39b025529dfbfcac9e
diff --git a/trunk/arch/x86/kernel/cpu/perf_event.c b/trunk/arch/x86/kernel/cpu/perf_event.c
index 817d2b195e8e..ce27c547fe78 100644
--- a/trunk/arch/x86/kernel/cpu/perf_event.c
+++ b/trunk/arch/x86/kernel/cpu/perf_event.c
@@ -375,15 +375,53 @@ static void release_pmc_hardware(void) {}
 static bool check_hw_exists(void)
 {
 	u64 val, val_new = 0;
-	int ret = 0;
+	int i, reg, ret = 0;
+
+	/*
+	 * Check to see if the BIOS enabled any of the counters, if so
+	 * complain and bail.
+	 */
+	for (i = 0; i < x86_pmu.num_counters; i++) {
+		reg = x86_pmu.eventsel + i;
+		ret = rdmsrl_safe(reg, &val);
+		if (ret)
+			goto msr_fail;
+		if (val & ARCH_PERFMON_EVENTSEL_ENABLE)
+			goto bios_fail;
+	}
+
+	if (x86_pmu.num_counters_fixed) {
+		reg = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
+		ret = rdmsrl_safe(reg, &val);
+		if (ret)
+			goto msr_fail;
+		for (i = 0; i < x86_pmu.num_counters_fixed; i++) {
+			if (val & (0x03 << i*4))
+				goto bios_fail;
+		}
+	}
 
+	/*
+	 * Now write a value and read it back to see if it matches,
+	 * this is needed to detect certain hardware emulators (qemu/kvm)
+	 * that don't trap on the MSR access and always return 0s.
+	 */
 	val = 0xabcdUL;
-	ret |= checking_wrmsrl(x86_pmu.perfctr, val);
+	ret = checking_wrmsrl(x86_pmu.perfctr, val);
 	ret |= rdmsrl_safe(x86_pmu.perfctr, &val_new);
 	if (ret || val != val_new)
-		return false;
+		goto msr_fail;
 
 	return true;
+
+bios_fail:
+	printk(KERN_CONT "Broken BIOS detected, using software events only.\n");
+	printk(KERN_ERR FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n", reg, val);
+	return false;
+
+msr_fail:
+	printk(KERN_CONT "Broken PMU hardware detected, using software events only.\n");
+	return false;
 }
 
 static void reserve_ds_buffers(void);
@@ -1378,10 +1416,8 @@ int __init init_hw_perf_events(void)
 	pmu_check_apic();
 
 	/* sanity check that the hardware exists or is emulated */
-	if (!check_hw_exists()) {
-		pr_cont("Broken PMU hardware detected, software events only.\n");
+	if (!check_hw_exists())
 		return 0;
-	}
 
 	pr_cont("%s PMU driver.\n", x86_pmu.name);