KVM: Communicate cr8 changes to userspace

This allows running 64-bit Windows.
Signed-off-by: NSheng Yang <sheng.yang@intel.com>
Signed-off-by: NAvi Kivity <avi@qumranet.com>

drivers/kvm/vmx.c

@@ -1831,7 +1831,8 @@ static int handle_cr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 			vcpu_load_rsp_rip(vcpu);
 			set_cr8(vcpu, vcpu->regs[reg]);
 			skip_emulated_instruction(vcpu);
-			return 1;
+			kvm_run->exit_reason = KVM_EXIT_SET_TPR;
+			return 0;
 		};
 		break;
 	case 2: /* clts */

include/linux/kvm.h

@@ -46,6 +46,7 @@ enum kvm_exit_reason {
 	KVM_EXIT_SHUTDOWN         = 8,
 	KVM_EXIT_FAIL_ENTRY       = 9,
 	KVM_EXIT_INTR             = 10,
+	KVM_EXIT_SET_TPR          = 11
 };
 
 /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */