Re: [Qemu-devel] vgabios + qemu: issues and plans.

[Isaku Yamahata <yamahata@valinux.co.jp>]

On Wed, May 05, 2010 at 03:38:21PM +0200, Gerd Hoffmann wrote:
>   Hi,
>
> Today we have two vgabios versions in qemu:  The standard one  
> (vgabios.bin) and the cirrus one (vgabios-cirrus.bin).
>
> The cirrus vgabios is a PCI ROM.  We can (and do) load it into the ROM  
> PCI bar.  The vgabios checks the pci config space to figure where the  
> linear framebuffer (for vesa graphics) is mapped to.  It knows how to  
> program the cirrus.
>
> The standard bios isn't a PCI ROM.  We have to load it using the seabios  
> firmware interface.  It expects to find the linear framebuffer at the  
> magic address 0xe0000000.  It uses the bochs extentions to implement  
> vesa graphics support.
>
> So, what is wrong with this?
>
> First, I'd like to be able to load the vgabios via PCI ROM bar on all  
> pci vga cards (stdvga, vmware, soon qxl).  The PCI ID in the bios has to  
> match the PCI ID of the card, so we'll need a bunch of vga bios  
> binaries, all identical except for the PCI ID.  Or we need some kind of  
> binary patching.  Otherwise seabios will not load them from the PCI ROM 
> bar.

Make vga bios aware of all ids?
Then single vga bios image can handle all vga devices.
If new device is introduced (qxl), new id will be added to id table
I thing that adding a new vga device is rare.
Or do you want to more generic/dynamic solution?


> Second, I want to get rid of the magic address 0xe0000000 (except for  
> isa-vga).  This is basically just a matter of updating to vgabios  
> version 0.6c.  And this needs one vga bios binary per vga card too as  
> the PCI ID is used to lookup the card (and then the framebuffer address)  
> in PCI config space.

I also want to eliminate the magic number.
Boch vga bios is paravirtualized to get VBE address dynamically via a new
pci device with special pci device of device id 0x1234.
Are you meaning to follow bochs way?

Or how about to use qemu fw interface to get the address dynamically?


>
> Comments?  Especially on the binary patching?  Worth it?  Or just build  
> a bunch of binaries?  They are not *that* big after all ...
>
> cheers,
>   Gerd
>
>

-- 
yamahata