add bochs dispi interface framebuffer driver

This patchs adds a frame buffer driver for (virtual/emulated) vga cards
implementing the bochs dispi interface.  Supported hardware are the
bochs vga card with vbe extension and the qemu standard vga.

The driver uses a fixed depth of 32bpp.  Otherwise it supports the full
(but small) feature set of the bochs dispi interface:  Resolution
switching and display panning.  It is tweaked to maximize fbcon speed,
so you'll get the comfort of the framebuffer console in kvm guests
without performance penalty.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 drivers/video/Kconfig   |   18 +++
 drivers/video/Makefile  |    1 +
 drivers/video/bochsfb.c |  385 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 404 insertions(+), 0 deletions(-)
 create mode 100644 drivers/video/bochsfb.c

Hi,

On Thu, Mar 08, 2012 at 11:13:46AM +0100, Gerd Hoffmann wrote:
> This patchs adds a frame buffer driver for (virtual/emulated) vga cards
> implementing the bochs dispi interface.  Supported hardware are the
> bochs vga card with vbe extension and the qemu standard vga.
> 
> The driver uses a fixed depth of 32bpp.  Otherwise it supports the full
> (but small) feature set of the bochs dispi interface:  Resolution
> switching and display panning.  It is tweaked to maximize fbcon speed,
> so you'll get the comfort of the framebuffer console in kvm guests
> without performance penalty.

I am testing this driver with qemu-kvm-1.2 or qemu-kvm master (commit)
and "-std vga". The driver works fine in general.

When I test a guest that runs X (ubuntu-12.04 desktop amd64), sometimes parts of
the screen and keyboard input is mixed between the X terminal and fbconsole
terminals. This happens only on the initial X11 login (right after boot or
reboot) and only sometimes.

During this time, there is a second keyboard cursor at top of the screen on the
X11 login. When switching to an fbconsole (ctrl+alt+f1), screen output of the X11
login screen gets mixed with fbconsole screen. And vice-versa when I go back to the
X11 terminal(I can send you 2 screendumps if needed, I haven't attached them here
due to size)
If I try to login (pressing enter), the X11-login is redrawn and from then on vt
switching works with no problems (I have to retype login, I am not sure where the
original keyboard input goes to)

Xorg driver used is fbdev (i can send xorg log), not sure if another driver
should be used/implemented for the bochsfb.

According to "xrandr -q" same resolution as bochsfb is used:
Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
    1024x768    116.0*

"fbset -i" output is as expected:

mode "1024x768-116"
    # D: 100.000 MHz, H: 93.985 kHz, V: 116.318 Hz
    geometry 1024 768 1024 4096 32
    timings 10000 16 16 16 16 8 8
    rgba 8/16,8/8,8/0,8/24
endmode

Frame buffer device information:
    Name        : bochsfb
    Address     : 0xfd000000
    Size        : 16777216
    Type        : PACKED PIXELS
    Visual      : TRUECOLOR
    XPanStep    : 1
    YPanStep    : 1
    YWrapStep   : 0
    LineLength  : 4096
    Accelerator : No

Some framebuffer-relevant guest kernel options used:

CONFIG_FB_BOOT_VESA_SUPPORT=y
CONFIG_FB_CFB_FILLRECT=y
CONFIG_FB_CFB_COPYAREA=y
CONFIG_FB_CFB_IMAGEBLIT=y
# CONFIG_FB_CFB_REV_PIXELS_IN_BYTE is not set
CONFIG_FB_DEFERRED_IO=y
#
# Frame buffer hardware drivers
#
CONFIG_FB_BOCHS=m
CONFIG_FB_VESA=y
# CONFIG_FB_EFI is not set

Should FB_VESA be turned to "not set" for this test? (it's not tristate in Kconfig)

Btw (slightly off-topic) are other framebuffer drivers suitable for the
standard qemu vga-pci device? Would vesafb or uvesafb work? 

I haven't been able to load uvesafb in a guest, because the userspace helper
program v86d segfaults (maybe it tries to access vga ioports that are not
implemented in qemu?)

> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  drivers/video/Kconfig   |   18 +++
>  drivers/video/Makefile  |    1 +
>  drivers/video/bochsfb.c |  385 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 404 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/video/bochsfb.c
> 
> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> index 6ca0c40..4d21f90 100644
> --- a/drivers/video/Kconfig
> +++ b/drivers/video/Kconfig
> @@ -286,6 +286,24 @@ config FB_CIRRUS
>  	  Say N unless you have such a graphics board or plan to get one
>  	  before you next recompile the kernel.
>  
> +config FB_BOCHS
> +	tristate "Bochs dispi interface support"
> +	depends on FB && PCI
> +	select FB_CFB_FILLRECT
> +	select FB_CFB_COPYAREA
> +	select FB_CFB_IMAGEBLIT
> +	---help---
> +	  This is the frame buffer driver for (virtual/emulated) vga
> +          cards implementing the bochs dispi interface.  Supported
> +          hardware are the bochs vga card with vbe extension and the
> +          qemu standard vga.
> +
> +          The driver handles the PCI variants only.  It uses a fixed
> +          depth of 32bpp, anything else doesn't make sense these days.
> +
> +          Say Y here if you plan to run the kernel in a virtual machine
> +          emulated by bochs or qemu.
> +
>  config FB_PM2
>  	tristate "Permedia2 support"
>  	depends on FB && ((AMIGA && BROKEN) || PCI)
> diff --git a/drivers/video/Makefile b/drivers/video/Makefile
> index 1426068..a065ad3 100644
> --- a/drivers/video/Makefile
> +++ b/drivers/video/Makefile
> @@ -99,6 +99,7 @@ obj-$(CONFIG_FB_ARMCLCD)	  += amba-clcd.o
>  obj-$(CONFIG_FB_68328)            += 68328fb.o
>  obj-$(CONFIG_FB_GBE)              += gbefb.o
>  obj-$(CONFIG_FB_CIRRUS)		  += cirrusfb.o
> +obj-$(CONFIG_FB_BOCHS)		  += bochsfb.o
>  obj-$(CONFIG_FB_ASILIANT)	  += asiliantfb.o
>  obj-$(CONFIG_FB_PXA)		  += pxafb.o
>  obj-$(CONFIG_FB_PXA168)		  += pxa168fb.o
> diff --git a/drivers/video/bochsfb.c b/drivers/video/bochsfb.c
> new file mode 100644
> index 0000000..18a94dc
> --- /dev/null
> +++ b/drivers/video/bochsfb.c
> @@ -0,0 +1,385 @@
> +/*
> + *  This file is subject to the terms and conditions of the GNU General Public
> + *  License. See the file COPYING in the main directory of this archive for
> + *  more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/mm.h>
> +#include <linux/vmalloc.h>
> +#include <linux/delay.h>
> +#include <linux/interrupt.h>
> +#include <linux/fb.h>
> +#include <linux/pm.h>
> +#include <linux/init.h>
> +#include <linux/pci.h>
> +#include <linux/console.h>
> +#include <asm/io.h>
> +
> +#define VBE_DISPI_IOPORT_INDEX           0x01CE
> +#define VBE_DISPI_IOPORT_DATA            0x01CF
> +
> +#define VBE_DISPI_INDEX_ID               0x0
> +#define VBE_DISPI_INDEX_XRES             0x1
> +#define VBE_DISPI_INDEX_YRES             0x2
> +#define VBE_DISPI_INDEX_BPP              0x3
> +#define VBE_DISPI_INDEX_ENABLE           0x4
> +#define VBE_DISPI_INDEX_BANK             0x5
> +#define VBE_DISPI_INDEX_VIRT_WIDTH       0x6
> +#define VBE_DISPI_INDEX_VIRT_HEIGHT      0x7
> +#define VBE_DISPI_INDEX_X_OFFSET         0x8
> +#define VBE_DISPI_INDEX_Y_OFFSET         0x9
> +#define VBE_DISPI_INDEX_VIDEO_MEMORY_64K 0xa
> +
> +#define VBE_DISPI_ID0                    0xB0C0
> +#define VBE_DISPI_ID1                    0xB0C1
> +#define VBE_DISPI_ID2                    0xB0C2
> +#define VBE_DISPI_ID3                    0xB0C3
> +#define VBE_DISPI_ID4                    0xB0C4
> +#define VBE_DISPI_ID5                    0xB0C5
> +
> +#define VBE_DISPI_DISABLED               0x00
> +#define VBE_DISPI_ENABLED                0x01
> +#define VBE_DISPI_GETCAPS                0x02
> +#define VBE_DISPI_8BIT_DAC               0x20
> +#define VBE_DISPI_LFB_ENABLED            0x40
> +#define VBE_DISPI_NOCLEARMEM             0x80
> +
> +enum bochs_types {
> +	BOCHS_QEMU_STDVGA,
> +	BOCHS_UNKNOWN,
> +};
> +
> +static const char *bochs_names[] = {
> +	[ BOCHS_QEMU_STDVGA ] = "QEMU standard vga",
> +	[ BOCHS_UNKNOWN ]     = "unknown",
> +};
> +
> +static struct fb_fix_screeninfo bochsfb_fix __devinitdata = {
> +	.id          = "bochsfb",
> +	.type        = FB_TYPE_PACKED_PIXELS,
> +	.visual      = FB_VISUAL_TRUECOLOR,
> +	.accel       = FB_ACCEL_NONE,
> +	.xpanstep    = 1,
> +	.ypanstep    = 1,
> +};
> +
> +static struct fb_var_screeninfo bochsfb_var __devinitdata = {
> +	.xres           = 1024,
> +	.yres           = 768,
> +	.bits_per_pixel = 32,
> +#ifdef __BIG_ENDIAN
> +	.transp         = { .length = 8, .offset =  0 },
> +	.red            = { .length = 8, .offset =  8 },
> +	.green          = { .length = 8, .offset = 16 },
> +	.blue           = { .length = 8, .offset = 24 },
> +#else
> +	.transp         = { .length = 8, .offset = 24 },
> +	.red            = { .length = 8, .offset = 16 },
> +	.green          = { .length = 8, .offset =  8 },
> +	.blue           = { .length = 8, .offset =  0 },
> +#endif
> +	.height         = -1,
> +	.width          = -1,
> +	.vmode          = FB_VMODE_NONINTERLACED,
> +	.pixclock       = 10000,
> +	.left_margin    = 16,
> +	.right_margin   = 16,
> +	.upper_margin   = 16,
> +	.lower_margin   = 16,
> +	.hsync_len      = 8,
> +	.vsync_len      = 8,
> +};
> +
> +static char *mode __devinitdata;
> +module_param(mode, charp, 0);
> +MODULE_PARM_DESC(mode, "Initial video mode e.g. '648x480'");
> +
> +static u16 bochs_read(u16 reg)
> +{
> +	outw(reg, VBE_DISPI_IOPORT_INDEX);
> +	return inw(VBE_DISPI_IOPORT_DATA);
> +}
> +
> +static void bochs_write(u16 reg, u16 val)
> +{
> +	outw(reg, VBE_DISPI_IOPORT_INDEX);
> +	outw(val, VBE_DISPI_IOPORT_DATA);
> +}
> +
> +static int bochsfb_check_var(struct fb_var_screeninfo *var,
> +			     struct fb_info *info)
> +{
> +	uint32_t x,y, xv,yv, pixels;
> +
> +	if (var->bits_per_pixel != 32 ||
> +	    var->xres > 65535 ||
> +	    var->xres_virtual > 65535 ||
> +	    (var->vmode & FB_VMODE_MASK) != FB_VMODE_NONINTERLACED)
> +		return -EINVAL;
> +
> +	x  = var->xres & ~0x0f;
> +	y  = var->yres & ~0x03;
> +	xv = var->xres_virtual & ~0x0f;
> +	yv = var->yres_virtual & ~0x03;
> +	if (xv < x)
> +		xv = x;
> +	pixels = info->fix.smem_len * 8 / info->var.bits_per_pixel;
> +	yv = pixels / xv;
> +	if (y > yv)
> +		return -EINVAL;
> +
> +	var->xres = x;
> +	var->yres = y;
> +	var->xres_virtual = xv;
> +	var->yres_virtual = yv;
> +	var->xoffset = 0;
> +	var->yoffset = 0;
> +
> +	return 0;
> +}
> +
> +static int bochsfb_set_par(struct fb_info *info)
> +{
> +	dev_dbg(info->dev, "set mode: real: %dx%d, virtual: %dx%d\n",
> +		info->var.xres, info->var.yres,
> +		info->var.xres_virtual, info->var.yres_virtual);
> +
> +	info->fix.line_length = info->var.xres * info->var.bits_per_pixel / 8;
> +
> +	bochs_write(VBE_DISPI_INDEX_BPP,         info->var.bits_per_pixel);
> +	bochs_write(VBE_DISPI_INDEX_XRES,        info->var.xres);
> +	bochs_write(VBE_DISPI_INDEX_YRES,        info->var.yres);
> +	bochs_write(VBE_DISPI_INDEX_BANK,        0);
> +	bochs_write(VBE_DISPI_INDEX_VIRT_WIDTH,  info->var.xres_virtual);
> +	bochs_write(VBE_DISPI_INDEX_VIRT_HEIGHT, info->var.yres_virtual);
> +	bochs_write(VBE_DISPI_INDEX_X_OFFSET,    info->var.xoffset);
> +	bochs_write(VBE_DISPI_INDEX_Y_OFFSET,    info->var.yoffset);
> +
> +	bochs_write(VBE_DISPI_INDEX_ENABLE,
> +		    VBE_DISPI_ENABLED | VBE_DISPI_LFB_ENABLED);
> +	return 0;
> +}
> +
> +static int bochsfb_setcolreg(unsigned regno, unsigned red, unsigned green,
> +			     unsigned blue, unsigned transp,
> +			     struct fb_info *info)
> +{
> +	if (regno < 16 && info->var.bits_per_pixel == 32) {
> +		red   >>= 8;
> +		green >>= 8;
> +		blue  >>= 8;
> +		((u32 *)(info->pseudo_palette))[regno] =
> +			(red   << info->var.red.offset)   |
> +			(green << info->var.green.offset) |
> +			(blue  << info->var.blue.offset);
> +	}
> +	return 0;
> +}
> +
> +static int bochsfb_pan_display(struct fb_var_screeninfo *var,
> +			       struct fb_info *info)
> +{
> +	bochs_write(VBE_DISPI_INDEX_X_OFFSET, var->xoffset);
> +	bochs_write(VBE_DISPI_INDEX_Y_OFFSET, var->yoffset);
> +	return 0;
> +}
> +
> +static struct fb_ops bochsfb_ops = {
> +	.owner	        = THIS_MODULE,
> +	.fb_check_var   = bochsfb_check_var,
> +	.fb_set_par     = bochsfb_set_par,
> +	.fb_setcolreg   = bochsfb_setcolreg,
> +	.fb_pan_display = bochsfb_pan_display,
> +	.fb_fillrect    = cfb_fillrect,
> +	.fb_copyarea    = cfb_copyarea,
> +	.fb_imageblit   = cfb_imageblit,
> +};
> +
> +static int __devinit
> +bochsfb_pci_init(struct pci_dev *dp, const struct pci_device_id *ent)
> +{
> +	struct fb_info *p;
> +	unsigned long addr, size, mem;
> +	u16 id;
> +	int rc = -ENODEV;
> +
> +	id = bochs_read(VBE_DISPI_INDEX_ID);;
> +	mem = bochs_read(VBE_DISPI_INDEX_VIDEO_MEMORY_64K) * 64 * 1024;
> +	dev_info(&dp->dev,"Found bochs VGA, ID 0x%x, mem %ldk, type \"%s\".\n",
> +		 id, mem / 1024, bochs_names[ent->driver_data]);
> +	if ((id & 0xfff0) != VBE_DISPI_ID0) {
> +		dev_err(&dp->dev, "ID mismatch\n");
> +		goto err_out;
> +	}
> +
> +	if (pci_enable_device(dp) < 0) {
> +		dev_err(&dp->dev, "Cannot enable PCI device\n");
> +		goto err_out;
> +	}
> +
> +	if ((dp->resource[0].flags & IORESOURCE_MEM) == 0)
> +		goto err_disable;
> +	addr = pci_resource_start(dp, 0);
> +	size = pci_resource_len(dp, 0);
> +	if (addr == 0)
> +		goto err_disable;
> +	if (size != mem) {
> +		dev_err(&dp->dev, "Size mismatch: pci=%ld, bochs=%ld\n", size, mem);
> +		size = min(size, mem);
> +	}
> +
> +	p = framebuffer_alloc(0, &dp->dev);
> +	if (p == NULL) {
> +		dev_err(&dp->dev, "Cannot allocate framebuffer structure\n");
> +		rc = -ENOMEM;
> +		goto err_disable;
> +	}
> +
> +	if (pci_request_region(dp, 0, "bochsfb") != 0) {
> +		dev_err(&dp->dev, "Cannot request framebuffer\n");
> +		rc = -EBUSY;
> +		goto err_release_fb;
> +	}
> +
> +	if (!request_region(VBE_DISPI_IOPORT_INDEX, 2, "bochsfb")) {
> +		dev_err(&dp->dev, "Cannot request ioports\n");
> +		rc = -EBUSY;
> +		goto err_release_pci;
> +	}
> +
> +	p->screen_base = ioremap(addr, size);
> +	if (p->screen_base == NULL) {
> +		dev_err(&dp->dev, "Cannot map framebuffer\n");
> +		rc = -ENOMEM;
> +		goto err_release_ports;
> +	}
> +	memset(p->screen_base, 0, size);
> +
> +	pci_set_drvdata(dp, p);
> +	p->fbops = &bochsfb_ops;
> +	p->flags = FBINFO_FLAG_DEFAULT
> +		| FBINFO_READS_FAST
> +		| FBINFO_HWACCEL_XPAN
> +		| FBINFO_HWACCEL_YPAN;
> +	p->pseudo_palette = kmalloc(sizeof(u32) * 16, GFP_KERNEL);
> +	p->fix = bochsfb_fix;
> +	p->fix.smem_start = addr;
> +	p->fix.smem_len = size;
> +
> +	p->var = bochsfb_var;
> +	bochsfb_check_var(&p->var, p);
> +	if (mode) {
> +		fb_find_mode(&p->var, p, mode, NULL, 0, NULL, 32);
> +	}
> +
> +	if (register_framebuffer(p) < 0) {
> +		dev_err(&dp->dev,"Framebuffer failed to register\n");
> +		goto err_unmap;
> +	}
> +
> +	dev_info(&dp->dev,"fb%d: bochs VGA frame buffer initialized.\n",
> +		 p->node);
> +
> +	return 0;
> +
> + err_unmap:
> +	iounmap(p->screen_base);
> + err_release_ports:
> +	release_region(VBE_DISPI_IOPORT_INDEX, 2);
> + err_release_pci:
> +	pci_release_region(dp, 0);
> + err_release_fb:
> +	framebuffer_release(p);
> + err_disable:
> + err_out:
> +	return rc;
> +}
> +
> +static void __devexit bochsfb_remove(struct pci_dev *dp)
> +{
> +	struct fb_info *p = pci_get_drvdata(dp);
> +
> +	if (p->screen_base == NULL)
> +		return;
> +	unregister_framebuffer(p);
> +	iounmap(p->screen_base);
> +	p->screen_base = NULL;
> +	release_region(VBE_DISPI_IOPORT_INDEX, 2);
> +	pci_release_region(dp, 0);
> +	kfree(p->pseudo_palette);
> +	framebuffer_release(p);
> +}
> +
> +static struct pci_device_id bochsfb_pci_tbl[] = {
> +	{
> +		.vendor      = 0x1234,
> +		.device      = 0x1111,
> +		.subvendor   = 0x1af4,
> +		.subdevice   = 0x1100,
> +		.driver_data = BOCHS_QEMU_STDVGA,
> +	},
> +	{
> +		.vendor      = 0x1234,
> +		.device      = 0x1111,
> +		.subvendor   = PCI_ANY_ID,
> +		.subdevice   = PCI_ANY_ID,
> +		.driver_data = BOCHS_UNKNOWN,
> +	},
> +	{ /* end of list */ }
> +};
> +
> +MODULE_DEVICE_TABLE(pci, bochsfb_pci_tbl);
> +
> +static struct pci_driver bochsfb_driver = {
> +	.name =		"bochsfb",
> +	.id_table =	bochsfb_pci_tbl,
> +	.probe =	bochsfb_pci_init,
> +	.remove =	__devexit_p(bochsfb_remove),
> +};
> +
> +#ifndef MODULE
> +static int __init bochsfb_setup(char *options)
> +{
> +	char *this_opt;
> +
> +	if (!options || !*options)
> +		return 0;
> +
> +	while ((this_opt = strsep(&options, ",")) != NULL) {
> +		if (!*this_opt)
> +			continue;
> +		if (!strncmp(this_opt, "mode:", 5))
> +			mode = this_opt + 5;
> +		else
> +			mode = this_opt;
> +	}
> +	return 0;
> +}
> +#endif
> +
> +int __init bochs_init(void)
> +{
> +#ifndef MODULE
> +	char *option = NULL;
> +
> +	if (fb_get_options("bochsfb", &option))
> +		return -ENODEV;
> +	bochsfb_setup(option);
> +#endif
> +	return pci_register_driver(&bochsfb_driver);
> +}
> +
> +module_init(bochs_init);
> +
> +static void __exit bochsfb_exit(void)
> +{
> +	pci_unregister_driver(&bochsfb_driver);
> +}
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Gerd Hoffmann <kraxel@redhat.com>");
> +MODULE_DESCRIPTION("bochs dispi interface framebuffer driver");
> -- 
> 1.7.1
> 
>

On 10/19/12 12:35, Vasilis Liaskovitis wrote:
> Hi,
> 
> On Thu, Mar 08, 2012 at 11:13:46AM +0100, Gerd Hoffmann wrote:
>> This patchs adds a frame buffer driver for (virtual/emulated) vga cards
>> implementing the bochs dispi interface.  Supported hardware are the
>> bochs vga card with vbe extension and the qemu standard vga.
>>
>> The driver uses a fixed depth of 32bpp.  Otherwise it supports the full
>> (but small) feature set of the bochs dispi interface:  Resolution
>> switching and display panning.  It is tweaked to maximize fbcon speed,
>> so you'll get the comfort of the framebuffer console in kvm guests
>> without performance penalty.
> 
> I am testing this driver with qemu-kvm-1.2 or qemu-kvm master (commit)
> and "-std vga". The driver works fine in general.
> 
> When I test a guest that runs X (ubuntu-12.04 desktop amd64), sometimes parts of
> the screen and keyboard input is mixed between the X terminal and fbconsole
> terminals. This happens only on the initial X11 login (right after boot or
> reboot) and only sometimes.

Only with bochsfb or with vesafb (+ fbdev xorg driver) too?

> Xorg driver used is fbdev (i can send xorg log), not sure if another driver
> should be used/implemented for the bochsfb.

Yes, that one is fine.

> CONFIG_FB_BOCHS=m
> CONFIG_FB_VESA=y
> # CONFIG_FB_EFI is not set
> 
> Should FB_VESA be turned to "not set" for this test? (it's not tristate in Kconfig)
> 
> Btw (slightly off-topic) are other framebuffer drivers suitable for the
> standard qemu vga-pci device? Would vesafb or uvesafb work? 

Never tried uvesafb.  vesafb will work too, but run with a fixed
resolution.  bochsfb allows you to change the display resolution at
runtime using fbset.  fbcon is faster too because bochsfb supports
display panning.

Latest version of the patch is here:
  http://www.kraxel.org/cgit/linux/commit/?h=bochsfb

cheers,
  Gerd

On Thu, Nov 01, 2012 at 02:30:35PM +0100, Gerd Hoffmann wrote:
> On 10/19/12 12:35, Vasilis Liaskovitis wrote:
> > Hi,
> > 
> > On Thu, Mar 08, 2012 at 11:13:46AM +0100, Gerd Hoffmann wrote:
> >> This patchs adds a frame buffer driver for (virtual/emulated) vga cards
> >> implementing the bochs dispi interface.  Supported hardware are the
> >> bochs vga card with vbe extension and the qemu standard vga.
> >>
> >> The driver uses a fixed depth of 32bpp.  Otherwise it supports the full
> >> (but small) feature set of the bochs dispi interface:  Resolution
> >> switching and display panning.  It is tweaked to maximize fbcon speed,
> >> so you'll get the comfort of the framebuffer console in kvm guests
> >> without performance penalty.
> > 
> > I am testing this driver with qemu-kvm-1.2 or qemu-kvm master (commit)
> > and "-std vga". The driver works fine in general.
> > 
> > When I test a guest that runs X (ubuntu-12.04 desktop amd64), sometimes parts of
> > the screen and keyboard input is mixed between the X terminal and fbconsole
> > terminals. This happens only on the initial X11 login (right after boot or
> > reboot) and only sometimes.
> 
> Only with bochsfb or with vesafb (+ fbdev xorg driver) too?

vt-switching with vesafb/X11 works fine on a grml 64-bit image.  However, xorg
uses vesa driver in this case, not fbdev (fbdev / fbdevhw xorg modules are
initially loaded but then unloaded). X11 uses 1280x768 and vesafb uses 1024x768
according to dmesg. 

But i haven't been able to test ubuntu+vesafb.  Ubuntu kernels use efifb
(CONFIG_FB_EFI=y) and fbconsoles don't work at all with this driver +
qemu/seabios/vgastd.

I have tried using a custom kernel (CONFIG_FB_EFI not set, CONFIG_FB_VESA=y) but
for some reason I can't load vesafb on ubuntu desktop. No fb drivers are
blacklisted, but no fb driver is loaded if I specify a vga text mode with "vga="
in the kernel command line. X11 still uses 1280x768 resolution here.

Anyway, these are screenshots of the original problem (messed up output with
bochsfb + fbdev-xorg on ubuntu 12.04 startup): 

vt7 http://picpaste.de/bochsfb-badstart-AirrXZuF.png
vt1 http://www.picpaste.de/bochsfb-badstart-f1-EO10MVdF.png

it still happens with the latest bochsfb driver (tested with 3.6.0 though, not
3.7.0-rc3 yet)

> 
> > Xorg driver used is fbdev (i can send xorg log), not sure if another driver
> > should be used/implemented for the bochsfb.
> 
> Yes, that one is fine.
> 
> > CONFIG_FB_BOCHS=m
> > CONFIG_FB_VESA=y
> > # CONFIG_FB_EFI is not set
> > 
> > Should FB_VESA be turned to "not set" for this test? (it's not tristate in Kconfig)
> > 
> > Btw (slightly off-topic) are other framebuffer drivers suitable for the
> > standard qemu vga-pci device? Would vesafb or uvesafb work? 
> 
> Never tried uvesafb.  vesafb will work too, but run with a fixed
> resolution.  bochsfb allows you to change the display resolution at
> runtime using fbset.  fbcon is faster too because bochsfb supports
> display panning.

I assume bochsfb is the way we want to go. I can send more detailed info on the
uvesafb issue if needed.

thanks,

- Vasilis

>> Only with bochsfb or with vesafb (+ fbdev xorg driver) too?
> 
> vt-switching with vesafb/X11 works fine on a grml 64-bit image.  However, xorg
> uses vesa driver in this case, not fbdev (fbdev / fbdevhw xorg modules are
> initially loaded but then unloaded). X11 uses 1280x768 and vesafb uses 1024x768
> according to dmesg. 

You should be able to force the fbdev driver using xorg.conf.

> But i haven't been able to test ubuntu+vesafb.  Ubuntu kernels use efifb
> (CONFIG_FB_EFI=y) and fbconsoles don't work at all with this driver +
> qemu/seabios/vgastd.

I think this is a grub2 setup issue.  Grub2 can pass gfx mode params to
the linux kernel in a way efifb is able to handle.

> vt7 http://picpaste.de/bochsfb-badstart-AirrXZuF.png
> vt1 http://www.picpaste.de/bochsfb-badstart-f1-EO10MVdF.png

> it still happens with the latest bochsfb driver (tested with 3.6.0 though, not
> 3.7.0-rc3 yet)

Most likely this is a guest-side bug and not specific to bochsfb.
Console switching depends on all parties being cooperative.  Nothing
stops an application writing to the framebuffer even it isn't running on
the foreground console.

cheers,
  Gerd