KVM: VMX: Avoid exit when setting cr8 if the local apic is in the kernel

With apic in userspace, we must exit to userspace after a cr8 write in order
to update the tpr.  But if the apic is in the kernel, the exit is unnecessary.

Noticed by Joerg Roedel.
Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/vmx.c

@@ -1973,6 +1973,8 @@ 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);
+			if (irqchip_in_kernel(vcpu->kvm))
+				return 1;
 			kvm_run->exit_reason = KVM_EXIT_SET_TPR;
 			return 0;
 		};