Re: graphics card pci passthrough success report

[Lennert Buytenhek <buytenh@wantstofly.org>]

On Thu, Sep 13, 2012 at 07:55:00AM +0200, Gerd Hoffmann wrote:

> Hi,

Hi,


> > - Apply the patches at the end of this mail to kvm and SeaBIOS to
> >   allow for more BAR space under 4G.  (The relevant BARs on the
> >   graphics cards _are_ 64 bit BARs, but kvm seemed to turn those
> >   into 32 bit BARs in the guest.)
> 
> Which qemu/seabios versions have you used?
> 
> qemu-1.2 (+ bundled seabios) should handle that just fine without
> patching.  There is no fixed I/O window any more, all memory space above
> lowmem is available for pci, i.e. if you give 2G to your guest
> everything above 0x80000000.
> 
> And if there isn't enougth address space below 4G (if you assign lot of
> memory to your guest so qemu keeps only the 0xe0000000 - 0xffffffff
> window free) seabios should try to map 64bit bars above 4G.

This was some time ago, on (L)ubuntu 12.04, which has qemu-kvm 1.0
and seabios 0.6.2.  We'll retry on a newer distro soon.


> > - Apply the hacky patch at the end of this mail to SeaBIOS to
> >   always skip initialising the Radeon's option ROMs, or the VM
> >   would hang inside the Radeon option ROM if you boot the VM
> >   without the default cirrus video.
> 
> A better way to handle that would probably be to add an pci passthrough
> config option to not expose the rom to the guest.
> 
> Any clue *why* the rom doesn't run?

No idea, we didn't look into that -- this was just a one afternoon
hacking session.


thanks,
Lennert