Hi,> BTW can we teach virtio-gpu to look for framebuffer using > virtio pci caps?The virtio-gpu driver doesn't matter much here, it doesn't use it anyway.> Or are there limitations such as only > using IO port BARs, or compatibility with > BIOS code etc that limit us to specific BARs anyway?Yes, vgabios code needs to know. Currently it has bar #2 for the vga framebuffer bar hardcoded. It's 16bit code. I don't feel like making the probing more complicated ... cheers, Gerd
On Wed, Mar 25, 2015 at 04:37:16PM +0100, Gerd Hoffmann wrote:> Hi, > > > BTW can we teach virtio-gpu to look for framebuffer using > > virtio pci caps? > > The virtio-gpu driver doesn't matter much here, it doesn't use it > anyway. > > > Or are there limitations such as only > > using IO port BARs, or compatibility with > > BIOS code etc that limit us to specific BARs anyway? > > Yes, vgabios code needs to know. Currently it has bar #2 for the vga > framebuffer bar hardcoded. It's 16bit code. I don't feel like making > the probing more complicated ... > > cheers, > GerdOK - you are saying all VGA cards use bar #2 for this functionality, so we are just following established practice here? -- MST
On Mi, 2015-03-25 at 18:09 +0100, Michael S. Tsirkin wrote:> On Wed, Mar 25, 2015 at 04:37:16PM +0100, Gerd Hoffmann wrote: > > Hi, > > > > > BTW can we teach virtio-gpu to look for framebuffer using > > > virtio pci caps? > > > > The virtio-gpu driver doesn't matter much here, it doesn't use it > > anyway. > > > > > Or are there limitations such as only > > > using IO port BARs, or compatibility with > > > BIOS code etc that limit us to specific BARs anyway? > > > > Yes, vgabios code needs to know. Currently it has bar #2 for the vga > > framebuffer bar hardcoded. It's 16bit code. I don't feel like making > > the probing more complicated ... > > > > cheers, > > Gerd > > OK - you are saying all VGA cards use bar #2 for this > functionality, so we are just following > established practice here?vgabios checks pci ids to figure. qxl+stdvga use bar #0, vmware-vga bar #1, virtio-vga bar #2. cheers, Gerd