1 files changed, 30 insertions, 22 deletions

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 782c456eaa01..84bee67141ad 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -518,10 +518,9 @@ static void __cpuinit early_init_amd(struct cpuinfo_x86 *c)
 static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 {
 	u32 dummy;
-
-#ifdef CONFIG_SMP
 	unsigned long long value;
 
+#ifdef CONFIG_SMP
 	/*
 	 * Disable TLB flush filter by setting HWCR.FFDIS on K8
 	 * bit 6 of msr C001_0015
@@ -559,12 +558,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 		 * (AMD Erratum #110, docId: 25759).
 		 */
 		if (c->x86_model < 0x14 && cpu_has(c, X86_FEATURE_LAHF_LM)) {
-			u64 val;
-
 			clear_cpu_cap(c, X86_FEATURE_LAHF_LM);
-			if (!rdmsrl_amd_safe(0xc001100d, &val)) {
-				val &= ~(1ULL << 32);
-				wrmsrl_amd_safe(0xc001100d, val);
+			if (!rdmsrl_amd_safe(0xc001100d, &value)) {
+				value &= ~(1ULL << 32);
+				wrmsrl_amd_safe(0xc001100d, value);
 			}
 		}
 
@@ -617,13 +614,12 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 	if ((c->x86 == 0x15) &&
 	    (c->x86_model >= 0x10) && (c->x86_model <= 0x1f) &&
 	    !cpu_has(c, X86_FEATURE_TOPOEXT)) {
-		u64 val;
 
-		if (!rdmsrl_safe(0xc0011005, &val)) {
-			val |= 1ULL << 54;
-			wrmsrl_safe(0xc0011005, val);
-			rdmsrl(0xc0011005, val);
-			if (val & (1ULL << 54)) {
+		if (!rdmsrl_safe(0xc0011005, &value)) {
+			value |= 1ULL << 54;
+			wrmsrl_safe(0xc0011005, value);
+			rdmsrl(0xc0011005, value);
+			if (value & (1ULL << 54)) {
 				set_cpu_cap(c, X86_FEATURE_TOPOEXT);
 				printk(KERN_INFO FW_INFO "CPU: Re-enabling "
 				  "disabled Topology Extensions Support\n");
@@ -637,11 +633,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 	 */
 	if ((c->x86 == 0x15) &&
 	    (c->x86_model >= 0x02) && (c->x86_model < 0x20)) {
-		u64 val;
 
-		if (!rdmsrl_safe(0xc0011021, &val) && !(val & 0x1E)) {
-			val |= 0x1E;
-			wrmsrl_safe(0xc0011021, val);
+		if (!rdmsrl_safe(0xc0011021, &value) && !(value & 0x1E)) {
+			value |= 0x1E;
+			wrmsrl_safe(0xc0011021, value);
 		}
 	}
 
@@ -703,13 +698,11 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 	if (c->x86 > 0x11)
 		set_cpu_cap(c, X86_FEATURE_ARAT);
 
-	/*
-	 * Disable GART TLB Walk Errors on Fam10h. We do this here
-	 * because this is always needed when GART is enabled, even in a
-	 * kernel which has no MCE support built in.
-	 */
 	if (c->x86 == 0x10) {
 		/*
+		 * Disable GART TLB Walk Errors on Fam10h. We do this here
+		 * because this is always needed when GART is enabled, even in a
+		 * kernel which has no MCE support built in.
 		 * BIOS should disable GartTlbWlk Errors themself. If
 		 * it doesn't do it here as suggested by the BKDG.
 		 *
@@ -723,6 +716,21 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 			mask |= (1 << 10);
 			wrmsrl_safe(MSR_AMD64_MCx_MASK(4), mask);
 		}
+
+		/*
+		 * On family 10h BIOS may not have properly enabled WC+ support,
+		 * causing it to be converted to CD memtype. This may result in
+		 * performance degradation for certain nested-paging guests.
+		 * Prevent this conversion by clearing bit 24 in
+		 * MSR_AMD64_BU_CFG2.
+		 *
+		 * NOTE: we want to use the _safe accessors so as not to #GP kvm
+		 * guests on older kvm hosts.
+		 */
+
+		rdmsrl_safe(MSR_AMD64_BU_CFG2, &value);
+		value &= ~(1ULL << 24);
+		wrmsrl_safe(MSR_AMD64_BU_CFG2, value);
 	}
 
 	rdmsr_safe(MSR_AMD64_PATCH_LEVEL, &c->microcode, &dummy);