1 files changed, 33 insertions, 22 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 84dd33e717fd..4e7bbc49b7e4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -93,16 +93,16 @@ module_param_named(ignore_msrs, ignore_msrs, bool, S_IRUGO | S_IWUSR);
 
 struct kvm_shared_msrs_global {
         int nr;
-        struct kvm_shared_msr {
-                u32 msr;
-                u64 value;
-        } msrs[KVM_NR_SHARED_MSRS];
+        u32 msrs[KVM_NR_SHARED_MSRS];
 };
 
 struct kvm_shared_msrs {
         struct user_return_notifier urn;
         bool registered;
-        u64 current_value[KVM_NR_SHARED_MSRS];
+        struct kvm_shared_msr_values {
+                u64 host;
+                u64 curr;
+        } values[KVM_NR_SHARED_MSRS];
 };
 
 static struct kvm_shared_msrs_global __read_mostly shared_msrs_global;
@@ -147,53 +147,64 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 static void kvm_on_user_return(struct user_return_notifier *urn)
 {
         unsigned slot;
-        struct kvm_shared_msr *global;
         struct kvm_shared_msrs *locals
                 = container_of(urn, struct kvm_shared_msrs, urn);
+        struct kvm_shared_msr_values *values;
 
         for (slot = 0; slot < shared_msrs_global.nr; ++slot) {
-                global = &shared_msrs_global.msrs[slot];
-                if (global->value != locals->current_value[slot]) {
-                        wrmsrl(global->msr, global->value);
-                        locals->current_value[slot] = global->value;
+                values = &locals->values[slot];
+                if (values->host != values->curr) {
+                        wrmsrl(shared_msrs_global.msrs[slot], values->host);
+                        values->curr = values->host;
                 }
         }
         locals->registered = false;
         user_return_notifier_unregister(urn);
 }
 
-void kvm_define_shared_msr(unsigned slot, u32 msr)
+static void shared_msr_update(unsigned slot, u32 msr)
 {
-        int cpu;
+        struct kvm_shared_msrs *smsr;
         u64 value;
 
+        smsr = &__get_cpu_var(shared_msrs);
+        /* only read, and nobody should modify it at this time,
+         * so don't need lock */
+        if (slot >= shared_msrs_global.nr) {
+                printk(KERN_ERR "kvm: invalid MSR slot!");
+                return;
+        }
+        rdmsrl_safe(msr, &value);
+        smsr->values[slot].host = value;
+        smsr->values[slot].curr = value;
+}
+
+void kvm_define_shared_msr(unsigned slot, u32 msr)
+{
         if (slot >= shared_msrs_global.nr)
                 shared_msrs_global.nr = slot + 1;
-        shared_msrs_global.msrs[slot].msr = msr;
-        rdmsrl_safe(msr, &value);
-        shared_msrs_global.msrs[slot].value = value;
-        for_each_online_cpu(cpu)
-                per_cpu(shared_msrs, cpu).current_value[slot] = value;
+        shared_msrs_global.msrs[slot] = msr;
+        /* we need ensured the shared_msr_global have been updated */
+        smp_wmb();
 }
 EXPORT_SYMBOL_GPL(kvm_define_shared_msr);
 
 static void kvm_shared_msr_cpu_online(void)
 {
         unsigned i;
-        struct kvm_shared_msrs *locals = &__get_cpu_var(shared_msrs);
 
         for (i = 0; i < shared_msrs_global.nr; ++i)
-                locals->current_value[i] = shared_msrs_global.msrs[i].value;
+                shared_msr_update(i, shared_msrs_global.msrs[i]);
 }
 
 void kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
 {
         struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
 
-        if (((value ^ smsr->current_value[slot]) & mask) == 0)
+        if (((value ^ smsr->values[slot].curr) & mask) == 0)
                 return;
-        smsr->current_value[slot] = value;
-        wrmsrl(shared_msrs_global.msrs[slot].msr, value);
+        smsr->values[slot].curr = value;
+        wrmsrl(shared_msrs_global.msrs[slot], value);
         if (!smsr->registered) {
                 smsr->urn.on_user_return = kvm_on_user_return;
                 user_return_notifier_register(&smsr->urn);