kvm tools: Fix VESA BIOS mode info

Some VGA data such as VESA info needs a proper tuning for addresses
passed on kernel requests.  We returned linear addresses there while
spec points out that far pointers are needed.

This fixes a long-standing issue that caused Linux kernel to never exit
the mode scanning loop in arch/x86/boot/video-vesa.c::vesa_probe()
because returned mode info table segment/offset pair was bogus. The
issue triggered on some machines when CONFIG_FB_VESA was disabled.

Also use already VESA structures defined in <boot/vesa.h> header now
that we no longer use the struct to store VESA BIOS data.

Reported-by: Pekka Enberg <penberg@kernel.org>
CC: Sasha Levin <levinsasha928@gmail.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Asias He <asias.hejun@gmail.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
[ penberg@kernel.org: minor cleanups to setup_vga_rom() ]
Signed-off-by: Pekka Enberg <penberg@kernel.org>

Makefile

@@ -225,6 +225,7 @@ BIOS_CFLAGS += -march=i386
 BIOS_CFLAGS += -mregparm=3
 
 BIOS_CFLAGS += -fno-stack-protector
+BIOS_CFLAGS += -I../../arch/$(ARCH)
 
 bios.o: bios/bios.bin bios/bios-rom.h
 

bios.c

@@ -103,6 +103,20 @@ static void e820_setup(struct kvm *kvm)
 	e820->nr_map			= i;
 }
 
+static void setup_vga_rom(struct kvm *kvm)
+{
+	u16 *mode;
+	void *p;
+
+	p = guest_flat_to_host(kvm, VGA_ROM_OEM_STRING);
+	memset(p, 0, VGA_ROM_OEM_STRING_SIZE);
+	strncpy(p, "KVM VESA", VGA_ROM_OEM_STRING_SIZE);
+
+	mode = guest_flat_to_host(kvm, VGA_ROM_MODES);
+	mode[0]	= 0x0112;
+	mode[1] = 0xffff;
+}
+
 /**
  * setup_bios - inject BIOS into guest memory
  * @kvm - guest system descriptor
@@ -137,6 +151,9 @@ void setup_bios(struct kvm *kvm)
 	/* E820 memory map must be present */
 	e820_setup(kvm);
 
+	/* VESA needs own tricks */
+	setup_vga_rom(kvm);
+
 	/*
 	 * Setup a *fake* real mode vector table, it has only
 	 * one real hadler which does just iret

bios/int10.c

@@ -4,59 +4,17 @@
 
 #include "bios/memcpy.h"
 
-#define VESA_MAGIC ('V' + ('E' << 8) + ('S' << 16) + ('A' << 24))
+#include <boot/vesa.h>
 
-/* VESA General Information table */
-struct vesa_general_info {
-	u32	signature;		/* 0 Magic number = "VESA" */
-	u16	version;		/* 4 */
-	void	*vendor_string;		/* 6 */
-	u32	capabilities;		/* 10 */
-	void	*video_mode_ptr;	/* 14 */
-	u16	total_memory;		/* 18 */
-	u16	modes[2];		/* 20 */
-	char	oem_string[11];		/* 24 */
+static far_ptr gen_far_ptr(unsigned int pa)
+{
+	far_ptr ptr;
 
-	u8	reserved[223];		/* 35 */
-} __attribute__ ((packed));
+	ptr.seg = (pa >> 4);
+	ptr.off = pa - (ptr.seg << 4);
 
-struct vminfo {
-	u16	mode_attr;		/* 0 */
-	u8	win_attr[2];		/* 2 */
-	u16	win_grain;		/* 4 */
-	u16	win_size;		/* 6 */
-	u16	win_seg[2];		/* 8 */
-	u32	win_scheme;		/* 12 */
-	u16	logical_scan;		/* 16 */
-
-	u16	h_res;			/* 18 */
-	u16	v_res;			/* 20 */
-	u8	char_width;		/* 22 */
-	u8	char_height;		/* 23 */
-	u8	memory_planes;		/* 24 */
-	u8	bpp;			/* 25 */
-	u8	banks;			/* 26 */
-	u8	memory_layout;		/* 27 */
-	u8	bank_size;		/* 28 */
-	u8	image_planes;		/* 29 */
-	u8	page_function;		/* 30 */
-
-	u8	rmask;			/* 31 */
-	u8	rpos;			/* 32 */
-	u8	gmask;			/* 33 */
-	u8	gpos;			/* 34 */
-	u8	bmask;			/* 35 */
-	u8	bpos;			/* 36 */
-	u8	resv_mask;		/* 37 */
-	u8	resv_pos;		/* 38 */
-	u8	dcm_info;		/* 39 */
-
-	u32	lfb_ptr;		/* 40 Linear frame buffer address */
-	u32	offscreen_ptr;		/* 44 Offscreen memory address */
-	u16	offscreen_size;		/* 48 */
-
-	u8	reserved[206];		/* 50 */
-};
+	return ptr;
+}
 
 static inline void outb(unsigned short port, unsigned char val)
 {
@@ -76,9 +34,9 @@ static inline void int10_putchar(struct biosregs *args)
 
 static void vbe_get_mode(struct biosregs *args)
 {
-	struct vminfo *info = (struct vminfo *) args->edi;
+	struct vesa_mode_info *info = (struct vesa_mode_info *) args->edi;
 
-	*info = (struct vminfo) {
+	*info = (struct vesa_mode_info) {
 		.mode_attr		= 0xd9, /* 11011011 */
 		.logical_scan		= VESA_WIDTH*4,
 		.h_res			= VESA_WIDTH,
@@ -105,12 +63,10 @@ static void vbe_get_info(struct biosregs *args)
 	info = (struct vesa_general_info) {
 		.signature		= VESA_MAGIC,
 		.version		= 0x102,
-		.vendor_string		= &infop->oem_string,
+		.vendor_string		= gen_far_ptr(VGA_ROM_BEGIN),
 		.capabilities		= 0x10,
-		.video_mode_ptr		= &infop->modes,
+		.video_mode_ptr		= gen_far_ptr(VGA_ROM_MODES),
 		.total_memory		= (4 * VESA_WIDTH * VESA_HEIGHT) / 0x10000,
-		.oem_string		= "KVM VESA",
-		.modes			= { 0x0112, 0xffff },
 	};
 
 	memcpy16(args->es, infop, args->ds, &info, sizeof(info));

include/kvm/bios.h

@@ -33,6 +33,10 @@
 #define VGA_RAM_END			0x000bffff
 
 #define VGA_ROM_BEGIN			0x000c0000
+#define VGA_ROM_OEM_STRING		VGA_ROM_BEGIN
+#define VGA_ROM_OEM_STRING_SIZE		16
+#define VGA_ROM_MODES			(VGA_ROM_OEM_STRING + VGA_ROM_OEM_STRING_SIZE)
+#define VGA_ROM_MODES_SIZE		32
 #define VGA_ROM_END			0x000c7fff
 
 /* we handle one page only */