Re: [Qemu-devel] [PATCH - V3] Port codes from qemu-kvm to support booting from SCSI disk image

[Gerd Hoffmann <kraxel@redhat.com>]

On 08/21/10 16:20, Kevin O'Connor wrote:
> On Fri, Aug 20, 2010 at 09:39:10AM -0500, Anthony Liguori wrote:
>> On 08/20/2010 09:09 AM, Gerd Hoffmann wrote:
>>> Been there, tried that.  It isn't *that* easy.  The PCI ID in the
>>> option rom header doesn't match the PCI ID of the emulated lsi, so
>>> seabios refuses to load it from the rom bar.
>>
>> Heh, I was wondering why it didn't work unless I put rombar=0 :-)
>>
>> Is this fixable in a reasonable way or does PCI ID in the option rom
>> represent a much newer device that would trigger issues with guest
>> drivers?
>
> The PCI spec requires that the PCI IDs match - this is done so that a
> single rom can store multiple optionroms.
>
> One could place the optionrom in fw_cfg with a "file" name of
> "pciXXXX,YYYY.rom".  SeaBIOS will then deploy that rom for every
> device that has the given vendor/devid.  (It wont require matching PCI
> IDs ids in the rom.)

Yea, this is exactly what "rombar=0" (property for pci devices) does: 
load the rom via fw_cfg instead of using the pci option rom bar ;)

cheers,
   Gerd