Re: In "pci_fixup_video" check if this is or should be theprimaryvideo d

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jan 19, 2014 at 07:04:29AM -0700, Alex Williamson wrote:
> On Sun, 2014-01-19 at 12:44 +0200, Michael S. Tsirkin wrote:
> > On Fri, Jan 17, 2014 at 07:43:30PM +0900, eiichiro.oiwa.nm@hitachi.com wrote:
> > > Because legacy VGA is only one device on x86 System, I think qemu has to emulate a bridge
> > > for legacy VGA. The VGA Enable bit on its bridge control register has to set to 1. The VGA
> > > Enable bit describes in Table 3-10 Bridge Control register. When there are two VGA cards 
> > > on the same system, I think its system needs two bridges for each device. These bridges
> > > need bridge control registers. One VGA Enable bit on its bridge for legacy VGA has to set
> > > to 1. Another VGA Enable bit for second VGA has to set to 0.
> > > 
> > > 
> > > >On Thu, Jan 16, 2014 at 7:16 PM,  <eiichiro.oiwa.nm@hitachi.com> wrote:
> > > >> I think qemu is breaking "PCI-to-PCI Bridge Architecture Specification Revison 1.2
> > > >> June 9, 2003 Chapter 12. VGA Support".
> > > >
> > > >And what exactly do you think qemu is doing wrong?  Chapter 12 is ten
> > > >pages long.  Is there something there that prohibits two VGA devices
> > > >on the same bus?  I'm not a qemu developer, but if I were, I would
> > > >need a better hint about what is wrong before I could fix it.
> > > >
> > > >Again, sorry if you said this already and I missed it.
> > > >
> > > >>>[+cc Michael, Jesse, David, qemu-devel]
> > > >>>
> > > >>>On Wed, Jan 15, 2014 at 8:58 PM,  <eiichiro.oiwa.nm@hitachi.com> wrote:
> > > >>>> I suggest you should not break the PCI specification, as a developer of proprietary
> > > >>>> hypervisor, but I think your patch is no problem.
> > > >>>> Your PCI structure is specialized structure for your virtual machine.
> > > >>>> Maybe, your virtual machine will be causing another problem on Linux or other kernels
> > > >>>> because of breaking the PCI specification.
> > > >>>
> > > >>>I assume you think qemu is breaking the PCI spec.  What exactly do you
> > > >>>think is broken?  Please give specific references to the spec.  This
> > > >>>conversation is pretty fragmented, and I came in late, so I apologize
> > > >>>if I missed this.
> > > >>>
> > > >>>Bjorn
> > > >>>
> > > >
> > 
> > None of the bridges included in QEMU implements VGA support.
> > The spec explicitly says its optional, so that's ok.
> > 
> > As a result, you need to put device which has to work in
> > VGA mode on the root bus, any device behind a bridge
> > won't work in VGA mode (but might work in non VGA mode).
> 
> The ioh3420 root ports support VGA, so a q35 model is an option for
> multiple VGA devices.

Hmm, you are right, I forgot you implemented this in March.
In fact, I see that you updated bridges to support VGA
so if user wants to put both devices behind bridges,
that's also possible.

-- 
MST