KVM: x86: Emulate should check #UD before #GP

Intel SDM table 6-2 ("Priority Among Simultaneous Exceptions and Interrupts")
shows that faults from decoding the next instruction got higher priority than
general protection.  Moving the protected-mode check before the CPL check to
avoid wrong exception on vm86 mode.

Signed-off-by: Nadav Amit <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

arch/x86/kvm/emulate.c

@@ -4801,6 +4801,12 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 				goto done;
 		}
 
+		/* Instruction can only be executed in protected mode */
+		if ((ctxt->d & Prot) && ctxt->mode < X86EMUL_MODE_PROT16) {
+			rc = emulate_ud(ctxt);
+			goto done;
+		}
+
 		/* Privileged instruction can be executed only in CPL=0 */
 		if ((ctxt->d & Priv) && ops->cpl(ctxt)) {
 			if (ctxt->d & PrivUD)
@@ -4810,12 +4816,6 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 			goto done;
 		}
 
-		/* Instruction can only be executed in protected mode */
-		if ((ctxt->d & Prot) && ctxt->mode < X86EMUL_MODE_PROT16) {
-			rc = emulate_ud(ctxt);
-			goto done;
-		}
-
 		/* Do instruction specific permission checks */
 		if (ctxt->d & CheckPerm) {
 			rc = ctxt->check_perm(ctxt);