Re: [Xen-devel] [Qemu-devel] [v2][PATCH 4/8] xen, gfx passthrough: reserve 00:02.0 for INTEL IGD

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 2014/6/26 10:00, Chen, Tiejun wrote:
> On 2014/6/26 7:04, Slutz, Donald Christopher wrote:
> > On 06/24/14 22:49, Chen, Tiejun wrote:
> > > On 2014/5/19 19:22, Gerd Hoffmann wrote:
> > > >    Hi,
> > > >
> > > > > I think '-vga none' just guarantees the qemu vga cards doesn't occupy
> > > > > 00:02.0, but this doesn't mean others use this specific slot since in
> > > > > qemu internal, we always pass -1 to assign a slot automatically to
> > > > > register a PCI device. So in some cases, we can't get this slot as we
> > > > > expect since that is already assigned previously before we need this.
> > > > Yes, -vga, -net nic, -drive if=scsi (maybe more) can internally create
> > > > pci devices with auto slot assignment, which will occupy slot 2 indeed.
> > > > Use -device instead to create the devices.
> > > >
> > > > > PCI: slot 2 function 0 not available for xen-pci-passthrough, in use
> > > > > by xen-platform
> > > > Ah, the xen platform device.  /me looks.  Ah, pc_xen_hvm_init creates
> > > > this automatically.  Two options here IMHO:
> > > >
> > > >    (1) Just move it somewhere else explicitly.  For example slot 3, or
> > > >        make it a southbridge function (say 00:01.7).
> > > >    (2) Don't create it automatically, instead expect management add it
> > > >        if needed, using -device xen-plaform,addr=...
> > > Gerd,
> > >
> > > Sorry I return this discussion again.
> > >
> > > As we discussed here, we should never use -vga xxx to avoid occupying
> > > slot 2. Instead, we will just use -device to create that emulated vga
> > > device as you said like this:
> > >
> > > -device VGA,vgamem_mb=8,addr=0x4
> > >
> > > But looks this may issue another problem. That is we can't see
> > > anything until the vga driver is initialized. I means if we pass
> > > `-device VGA,vgamem_mb=8,addr=0x4', qemu doesn't expose any vga
> > > interface to BIOS. Right? Or I'm still missing something.
> > I know for Xen that
> >
> > tools/firmware/hvmloader/acpi/dsdt.asl
> >
> > also needs to change:
> >
> >
> >               /* Make cirrues VGA S3 suspend/resume work in Windows
> > XP/2003 */
> >               Device (VGA)
> >               {
> > -               Name (_ADR, 0x00020000)
> > +               // Address of the VGA (device F function 0)
> > +               Name (_ADR, 0x000F0000)
With this change I still didn't see anything.

Thanks
Tiejun

> > is what I have for:
> >
> > -device VGA,vgamem_mb=8,addr=0xF.0x0
> Do you mean we need to sync devfn with the passed address to work the
> emulated VGA before the real graphic device driver is called?
>
> Thanks
> Tiejun
>
> > I am not sure, but think that QEMU without Xen does this acpi
> > adjustment at run time.
> >
> >
> > I also change seabios's config to include more VGA support but
> > not sure it is needed.
> >
> >       -Don Slutz
> >
> > > Thanks
> > > Tiejun
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