+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);
+
+ 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;
+ }
+ }
+ locals->registered = false;
+ user_return_notifier_unregister(urn);
+}
+
+void kvm_define_shared_msr(unsigned slot, u32 msr)
+{
+ int cpu;
+ u64 value;
+
+ 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;
+}
+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;
+}
+
+void kvm_set_shared_msr(unsigned slot, u64 value)
+{
+ struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
+
+ if (value == smsr->current_value[slot])
+ return;
+ smsr->current_value[slot] = value;
+ wrmsrl(shared_msrs_global.msrs[slot].msr, value);
+ if (!smsr->registered) {
+ smsr->urn.on_user_return = kvm_on_user_return;
+ user_return_notifier_register(&smsr->urn);
+ smsr->registered = true;
+ }
+}
+EXPORT_SYMBOL_GPL(kvm_set_shared_msr);
+