KVM: VMX: don't clobber segment AR if emulating invalid state

The ususable bit is important for determining state validity; don't
clobber it.

Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/vmx.c

@@ -1649,7 +1649,7 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu,
 	var->limit = vmcs_read32(sf->limit);
 	var->selector = vmcs_read16(sf->selector);
 	ar = vmcs_read32(sf->ar_bytes);
-	if (ar & AR_UNUSABLE_MASK)
+	if ((ar & AR_UNUSABLE_MASK) && !emulate_invalid_guest_state)
 		ar = 0;
 	var->type = ar & 15;
 	var->s = (ar >> 4) & 1;