[PATCH kvm-unit-tests 2/2] realmode: print to serial port

[Paolo Bonzini <pbonzini@redhat.com>]

The realmode test is still printing to the old debug port at 0xf1.
Use the serial port instead.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 x86/realmode.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/x86/realmode.c b/x86/realmode.c
index 71c8a7d..67582b5 100644
--- a/x86/realmode.c
+++ b/x86/realmode.c
@@ -1,3 +1,7 @@
+#ifndef USE_SERIAL
+#define USE_SERIAL
+#endif
+
 asm(".code16gcc");
 
 typedef unsigned char u8;
@@ -22,16 +26,73 @@ static int strlen(const char *str)
 	return n;
 }
 
+static void outb(u8 data, u16 port)
+{
+	asm volatile("out %0, %1" : : "a"(data), "d"(port));
+}
+
+#ifdef USE_SERIAL
+static int serial_iobase = 0x3f8;
+static int serial_inited = 0;
+
+static u8 inb(u16 port)
+{
+	u8 data;
+	asm volatile("in %1, %0" : "=a"(data) : "d"(port));
+	return data;
+}
+
+static void serial_outb(char ch)
+{
+	u8 lsr;
+
+	do {
+		lsr = inb(serial_iobase + 0x05);
+	} while (!(lsr & 0x20));
+
+	outb(ch, serial_iobase + 0x00);
+}
+
+static void serial_init(void)
+{
+	u8 lcr;
+
+	/* set DLAB */
+	lcr = inb(serial_iobase + 0x03);
+	lcr |= 0x80;
+	outb(lcr, serial_iobase + 0x03);
+
+	/* set baud rate to 115200 */
+	outb(0x01, serial_iobase + 0x00);
+	outb(0x00, serial_iobase + 0x01);
+
+	/* clear DLAB */
+	lcr = inb(serial_iobase + 0x03);
+	lcr &= ~0x80;
+	outb(lcr, serial_iobase + 0x03);
+}
+#endif
+
 static void print_serial(const char *buf)
 {
 	unsigned long len = strlen(buf);
-
+#ifdef USE_SERIAL
+	unsigned long i;
+	if (!serial_inited) {
+	    serial_init();
+	}
+
+	for (i = 0; i < len; i++) {
+	    serial_outb(buf[i]);
+	}
+#else
 	asm volatile ("addr32/rep/outsb" : "+S"(buf), "+c"(len) : "d"(0xf1));
+#endif
 }
 
 static void exit(int code)
 {
-        asm volatile("out %0, %1" : : "a"(code), "d"((short)0xf4));
+	outb(code, 0xf4);
 }
 
 struct regs {
-- 
1.8.1.4