kvm: Add force exit from tests

To make so we write any value to port 0 and
start kvm in --dbgtest mode so we are expecting
for this exit.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

Makefile

@@ -79,7 +79,7 @@ bios/int10.o: bios/int10.S bios/int10-real.S
 
 check: $(PROGRAM)
 	$(MAKE) -C tests
-	./$(PROGRAM) tests/pit/tick.bin
+	./$(PROGRAM) --dbgtest tests/pit/tick.bin
 .PHONY: check
 
 clean:

main.c

@@ -10,9 +10,11 @@
 #include <string.h>
 #include <stdio.h>
 
+unsigned int dbgtest_mode;
+
 static void usage(char *argv[])
 {
-	fprintf(stderr, "  usage: %s [--single-step] [--kernel=]<kernel-image>\n",
+	fprintf(stderr, "  usage: %s [--dbgtest] [--single-step] [--kernel=]<kernel-image>\n",
 		argv[0]);
 	exit(1);
 }
@@ -48,6 +50,9 @@ int main(int argc, char *argv[])
 		} else if (!strncmp("--params=", argv[i], 9)) {
 			kernel_cmdline = &argv[i][9];
 			continue;
+		} else if (!strncmp("--dbgtest", argv[i], 9)) {
+			dbgtest_mode = 1;
+			continue;
 		} else if (!strncmp("--single-step", argv[i], 13)) {
 			single_step = true;
 			continue;
@@ -126,6 +131,14 @@ int main(int argc, char *argv[])
 	}
 
 exit_kvm:
+
+	if (dbgtest_mode) {
+		if (kvm->kvm_run->exit_reason == KVM_EXIT_IO &&
+			kvm->kvm_run->io.port == 0)
+			fprintf(stderr, "KVM: this is an expected IO error\n");
+			goto out;
+	}
+
 	fprintf(stderr, "KVM exit reason: %" PRIu32 " (\"%s\")\n",
 		kvm->kvm_run->exit_reason, kvm_exit_reasons[kvm->kvm_run->exit_reason]);
 	if (kvm->kvm_run->exit_reason == KVM_EXIT_UNKNOWN)
@@ -135,7 +148,7 @@ exit_kvm:
 	kvm__show_registers(kvm);
 	kvm__show_code(kvm);
 	kvm__show_page_tables(kvm);
-
+out:
 	kvm__delete(kvm);
 
 	return 0;

tests/pit/tick.S

@@ -4,6 +4,8 @@
 #define TIMER_FREQ	1193182
 #define TIMER_DIV(x)	((TIMER_FREQ+(x)/2)/(x))
 
+#define DBG_PORT	0
+
 #define TEST_COUNT	0x0200
 
 	.code16gcc
@@ -72,7 +74,9 @@ test_ok:
 	cs lea	msg2, %si
 	mov	$(msg2_end-msg2), %cx
 	cs rep/outsb
-	hlt
+
+	/* not a valid port to force exit */
+	outb	%al, $DBG_PORT
 
 timer_isr:
 	cli