kvm: Add support for early serial printk

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

Makefile

@@ -10,6 +10,7 @@ export E Q
 PROGRAM	= kvm
 
 OBJS	+= cpuid.o
+OBJS	+= early_printk.o
 OBJS	+= interrupt.o
 OBJS	+= ioport.o
 OBJS	+= kvm.o

early_printk.c

@@ -0,0 +1,37 @@
+#include "kvm/early_printk.h"
+
+#include "kvm/ioport.h"
+
+#include <stdio.h>
+
+static bool early_serial_txr_out(struct kvm *self, uint16_t port, void *data, int size, uint32_t count)
+{
+	char *p = data;
+
+	printf("%c", *p);
+
+	return true;
+}
+
+static struct ioport_operations early_serial_txr_ops = {
+	.io_out		= early_serial_txr_out,
+};
+
+static bool early_serial_lsr_in(struct kvm *self, uint16_t port, void *data, int size, uint32_t count)
+{
+	uint8_t *p = data;
+
+	*p	= 0x20;	/* xmtrdy */
+
+	return true;
+}
+
+static struct ioport_operations early_serial_lsr_ops = {
+	.io_in		= early_serial_lsr_in,
+};
+
+void early_printk__init(void)
+{
+	ioport__register(0x03F8, &early_serial_txr_ops);
+	ioport__register(0x03FD, &early_serial_lsr_ops);
+}

include/kvm/early_printk.h

@@ -0,0 +1,6 @@
+#ifndef KVM__EARLY_PRINTK_H
+#define KVM__EARLY_PRINTK_H
+
+void early_printk__init(void);
+
+#endif /* KVM__EARLY_PRINTK_H */

include/kvm/ioport.h

@@ -0,0 +1,16 @@
+#ifndef KVM__IOPORT_H
+#define KVM__IOPORT_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+struct kvm;
+
+struct ioport_operations {
+	bool (*io_in)(struct kvm *self, uint16_t port, void *data, int size, uint32_t count);
+	bool (*io_out)(struct kvm *self, uint16_t port, void *data, int size, uint32_t count);
+};
+
+void ioport__register(uint16_t port, struct ioport_operations *ops);
+
+#endif /* KVM__IOPORT_H */

ioport.c

@@ -1,13 +1,11 @@
+#include "kvm/ioport.h"
+
 #include "kvm/kvm.h"
 
+#include <assert.h>
 #include <limits.h>
 #include <stdio.h>
 
-struct ioport_operations {
-	bool (*io_in)(struct kvm *self, uint16_t port, void *data, int size, uint32_t count);
-	bool (*io_out)(struct kvm *self, uint16_t port, void *data, int size, uint32_t count);
-};
-
 static uint8_t ioport_to_uint8(void *data)
 {
 	uint8_t *p = data;
@@ -81,12 +79,23 @@ static struct ioport_operations *ioport_ops[USHRT_MAX] = {
 	[0x3D4]		= &dummy_read_write_ioport_ops,
 	[0x3D5]		= &dummy_write_only_ioport_ops,
 
+	/* PORT 03F8-03FF - Serial port (8250,8250A,8251,16450,16550,16550A,etc.) COM1 */
+	[0x03F9]	= &dummy_read_write_ioport_ops,
+	[0x03FA]	= &dummy_read_write_ioport_ops,
+	[0x03FB]	= &dummy_read_write_ioport_ops,
+	[0x03FC]	= &dummy_read_write_ioport_ops,
+
 	/* PORT 0CF8-0CFF - PCI Configuration Mechanism 1 - Configuration Registers */
 	[0x0CF8]	= &dummy_write_only_ioport_ops,
 	[0x0CFC]	= &dummy_read_write_ioport_ops,
 	[0x0CFE]	= &dummy_read_write_ioport_ops,
 };
 
+void ioport__register(uint16_t port, struct ioport_operations *ops)
+{
+	ioport_ops[port]	= ops;
+}
+
 static const char *to_direction(int direction)
 {
 	if (direction == KVM_EXIT_IO_IN)

main.c

@@ -1,5 +1,6 @@
 #include "kvm/kvm.h"
 
+#include "kvm/early_printk.h"
 #include "kvm/util.h"
 
 #include <inttypes.h>
@@ -58,6 +59,8 @@ int main(int argc, char *argv[])
 	if (single_step)
 		kvm__enable_singlestep(kvm);
 
+	early_printk__init();
+
 	for (;;) {
 		kvm__run(kvm);