diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index a7b6dec6fc3f4afc72f57651b1523156d415431b..0a60d60ed036b264e6d4c05174dfc3b464574852 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -235,8 +235,9 @@ static int iommu_completion_wait(struct amd_iommu *iommu)
 	status &= ~MMIO_STATUS_COM_WAIT_INT_MASK;
 	writel(status, iommu->mmio_base + MMIO_STATUS_OFFSET);
 
-	if (unlikely((i == EXIT_LOOP_COUNT) && printk_ratelimit()))
-		printk(KERN_WARNING "AMD IOMMU: Completion wait loop failed\n");
+	if (unlikely(i == EXIT_LOOP_COUNT))
+		panic("AMD IOMMU: Completion wait loop failed\n");
+
 out:
 	spin_unlock_irqrestore(&iommu->lock, flags);
 
diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 30ae2701b3df1b8976400d5996ed72a4a98baeea..c6cc22815d35f232dd21fae7d2718a3c161b373c 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -427,6 +427,10 @@ static u8 * __init alloc_command_buffer(struct amd_iommu *iommu)
 	memcpy_toio(iommu->mmio_base + MMIO_CMD_BUF_OFFSET,
 			&entry, sizeof(entry));
 
+	/* set head and tail to zero manually */
+	writel(0x00, iommu->mmio_base + MMIO_CMD_HEAD_OFFSET);
+	writel(0x00, iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
+
 	iommu_feature_enable(iommu, CONTROL_CMDBUF_EN);
 
 	return cmd_buf;
@@ -1074,7 +1078,8 @@ int __init amd_iommu_init(void)
 		goto free;
 
 	/* IOMMU rlookup table - find the IOMMU for a specific device */
-	amd_iommu_rlookup_table = (void *)__get_free_pages(GFP_KERNEL,
+	amd_iommu_rlookup_table = (void *)__get_free_pages(
+			GFP_KERNEL | __GFP_ZERO,
 			get_order(rlookup_table_size));
 	if (amd_iommu_rlookup_table == NULL)
 		goto free;
diff --git a/arch/x86/kernel/cpu/mcheck/mce_64.c b/arch/x86/kernel/cpu/mcheck/mce_64.c
index 4b031a4ac8562d3ed69f14f0d750dfe8519a057e..1c838032fd3732fde9bff776cbb63a2821115d60 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_64.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_64.c
@@ -510,12 +510,9 @@ static void __cpuinit mce_cpu_features(struct cpuinfo_x86 *c)
  */
 void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
 {
-	static cpumask_t mce_cpus = CPU_MASK_NONE;
-
 	mce_cpu_quirks(c);
 
 	if (mce_dont_init ||
-	    cpu_test_and_set(smp_processor_id(), mce_cpus) ||
 	    !mce_available(c))
 		return;
 
diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index 82fb2809ce32208eacd7231c38597938031d4036..c4b5b24e0217c585cbb8d0f8011a8b6c87229a6f 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -272,13 +272,18 @@ static struct attribute_group mc_attr_group = {
 	.name = "microcode",
 };
 
-static void microcode_fini_cpu(int cpu)
+static void __microcode_fini_cpu(int cpu)
 {
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
-	mutex_lock(&microcode_mutex);
 	microcode_ops->microcode_fini_cpu(cpu);
 	uci->valid = 0;
+}
+
+static void microcode_fini_cpu(int cpu)
+{
+	mutex_lock(&microcode_mutex);
+	__microcode_fini_cpu(cpu);
 	mutex_unlock(&microcode_mutex);
 }
 
@@ -306,12 +311,16 @@ static int microcode_resume_cpu(int cpu)
 	 * to this cpu (a bit of paranoia):
 	 */
 	if (microcode_ops->collect_cpu_info(cpu, &nsig)) {
-		microcode_fini_cpu(cpu);
+		__microcode_fini_cpu(cpu);
+		printk(KERN_ERR "failed to collect_cpu_info for resuming cpu #%d\n",
+				cpu);
 		return -1;
 	}
 
-	if (memcmp(&nsig, &uci->cpu_sig, sizeof(nsig))) {
-		microcode_fini_cpu(cpu);
+	if ((nsig.sig != uci->cpu_sig.sig) || (nsig.pf != uci->cpu_sig.pf)) {
+		__microcode_fini_cpu(cpu);
+		printk(KERN_ERR "cached ucode doesn't match the resuming cpu #%d\n",
+				cpu);
 		/* Should we look for a new ucode here? */
 		return 1;
 	}
diff --git a/arch/x86/kernel/microcode_intel.c b/arch/x86/kernel/microcode_intel.c
index 622dc4a217848d1c8d16941796a4f82f868fc967..a8e62792d171c6c63645582441b3d9482fffcbac 100644
--- a/arch/x86/kernel/microcode_intel.c
+++ b/arch/x86/kernel/microcode_intel.c
@@ -155,6 +155,7 @@ static DEFINE_SPINLOCK(microcode_update_lock);
 static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
 {
 	struct cpuinfo_x86 *c = &cpu_data(cpu_num);
+	unsigned long flags;
 	unsigned int val[2];
 
 	memset(csig, 0, sizeof(*csig));
@@ -174,11 +175,16 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
 		csig->pf = 1 << ((val[1] >> 18) & 7);
 	}
 
+	/* serialize access to the physical write to MSR 0x79 */
+	spin_lock_irqsave(&microcode_update_lock, flags);
+
 	wrmsr(MSR_IA32_UCODE_REV, 0, 0);
 	/* see notes above for revision 1.07.  Apparent chip bug */
 	sync_core();
 	/* get the current revision from MSR 0x8B */
 	rdmsr(MSR_IA32_UCODE_REV, val[0], csig->rev);
+	spin_unlock_irqrestore(&microcode_update_lock, flags);
+
 	pr_debug("microcode: collect_cpu_info : sig=0x%x, pf=0x%x, rev=0x%x\n",
 			csig->sig, csig->pf, csig->rev);
 
diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index ba7ad83e20a8f80d5b0ca7de95d6c1c0fbe6b27c..a35eaa379ff632fb142367df58a8fdeaaad81267 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -745,10 +745,8 @@ void __init gart_iommu_init(void)
 	unsigned long scratch;
 	long i;
 
-	if (cache_k8_northbridges() < 0 || num_k8_northbridges == 0) {
-		printk(KERN_INFO "PCI-GART: No AMD GART found.\n");
+	if (cache_k8_northbridges() < 0 || num_k8_northbridges == 0)
 		return;
-	}
 
 #ifndef CONFIG_AGP_AMD64
 	no_agp = 1;