KVM: x86 emulator: don't update vcpu state if instruction is restarted

No need to update vcpu state since instruction is in the middle of the
emulation.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

@@ -4057,32 +4057,27 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
 		return handle_emulation_failure(vcpu);
 	}
 
-	toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
-	kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
-	memcpy(vcpu->arch.regs, c->regs, sizeof c->regs);
-	kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.eip);
+	r = EMULATE_DONE;
 
-	if (vcpu->arch.emulate_ctxt.exception >= 0) {
+	if (vcpu->arch.emulate_ctxt.exception >= 0)
 		inject_emulated_exception(vcpu);
-		return EMULATE_DONE;
-	}
-
-	if (vcpu->arch.pio.count) {
+	else if (vcpu->arch.pio.count) {
 		if (!vcpu->arch.pio.in)
 			vcpu->arch.pio.count = 0;
-		return EMULATE_DO_MMIO;
-	}
-
-	if (vcpu->mmio_needed) {
+		r = EMULATE_DO_MMIO;
+	} else if (vcpu->mmio_needed) {
 		if (vcpu->mmio_is_write)
 			vcpu->mmio_needed = 0;
-		return EMULATE_DO_MMIO;
-	}
-
-	if (vcpu->arch.emulate_ctxt.restart)
+		r = EMULATE_DO_MMIO;
+	} else if (vcpu->arch.emulate_ctxt.restart)
 		goto restart;
 
-	return EMULATE_DONE;
+	toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
+	kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
+	memcpy(vcpu->arch.regs, c->regs, sizeof c->regs);
+	kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.eip);
+
+	return r;
 }
 EXPORT_SYMBOL_GPL(emulate_instruction);