1 files changed, 6 insertions, 0 deletions

diff --git a/arch/x86/kernel/microcode_intel.c b/arch/x86/kernel/microcode_intel.c
index 622dc4a21784..a8e62792d171 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);