Re: [Qemu-devel] [Xen-devel] [PATCH 0/5] xen: add Intel IGD passthrough support

[Ian Campbell]

On Fri, 2014-04-04 at 18:46 -0400, Kevin O'Connor wrote:
> On Fri, Feb 21, 2014 at 02:44:08PM +0800, Yang Zhang wrote:
> > From: Yang Zhang <address@hidden>
> > 
> > The following patches are ported from Xen Qemu-traditional branch which are
> > adding Intel IGD passthrough supporting to Qemu upstream.
> > 
> > To pass through IGD to guest, user need to add following lines in Xen config
> > file:
> > gfx_passthru=1
> > pci=['00:address@hidden']
> > 
> > Besides, since Xen + Qemu upstream is requiring seabios, user also need to
> > recompile seabios with CONFIG_OPTIONROMS_DEPLOYED=y to allow IGD pass 
> > through
> > successfully:
> 
> I'm not familiar with the Xen parts of your patch series.  However, I
> don't think one should be compiling SeaBIOS with
> CONFIG_OPTIONROMS_DEPLOYED enabled.

I agree, thanks for spotting this. I would nack any patch which tried to
enable this option in the Xen build of SeaBIOS.

>   That option was for very old
> versions of Bochs and QEMU that did not support fetching of optionroms
> directly from PCI config space nor from fw_cfg.
> 
> That compile time option is no longer well supported and it may be
> removed in the future.  I suggest looking at getting one of the other
> mechanisms working instead of using CONFIG_OPTIONROMS_DEPLOYED.

AFAIK the usual mechanisms already work for SeaBIOS under Xen, e.g. for
the video BIOS of the emulated VGA it Just Works. I've no idea what
makes Intel IGD passthrough special.

Ian.