KVM: VMX: Allow real mode emulation using vm86 with dpl=0

Real mode is always entered from protected mode with dpl=0.  Since
the dpl doesn't affect execution, and we already override it to 3
in the vmcs (as vmx requires), we can allow execution in that state.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/vmx.c

@@ -3317,7 +3317,7 @@ static bool rmode_segment_valid(struct kvm_vcpu *vcpu, int seg)
 		return false;
 	if (var.limit != 0xffff)
 		return false;
-	if (ar != 0xf3)
+	if ((ar | (3 << AR_DPL_SHIFT)) != 0xf3)
 		return false;
 
 	return true;