KVM: VMX: Optimize vmx_get_cpl()

Instead of calling vmx_get_segment() (which reads a whole bunch of
vmcs fields), read only the cs selector which contains the cpl.
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/vmx.c

@@ -1773,16 +1773,13 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu,
 
 static int vmx_get_cpl(struct kvm_vcpu *vcpu)
 {
-	struct kvm_segment kvm_seg;
-
 	if (!(vcpu->arch.cr0 & X86_CR0_PE)) /* if real mode */
 		return 0;
 
 	if (vmx_get_rflags(vcpu) & X86_EFLAGS_VM) /* if virtual 8086 */
 		return 3;
 
-	vmx_get_segment(vcpu, &kvm_seg, VCPU_SREG_CS);
-	return kvm_seg.selector & 3;
+	return vmcs_read16(GUEST_CS_SELECTOR) & 3;
 }
 
 static u32 vmx_segment_access_rights(struct kvm_segment *var)