Re: [Qemu-devel] [v5][PATCH 0/5] xen: add Intel IGD passthrough support

[Chen, Tiejun]

On 2014/6/25 16:48, Michael S. Tsirkin wrote:
> On Wed, Jun 25, 2014 at 10:39:43AM +0200, Paolo Bonzini wrote:
> > Il 25/06/2014 10:31, Michael S. Tsirkin ha scritto:
> > > It might be possible to move the Q35 bridge elsewhere.
> > > seabios doesn't care where the host bridge is.
> > > ACPI tables in QEMU can be adjusted.
> >
> > But why?  It's always in 00:1f.0 on real hardware.  If the i915 driver wants
> > to run under virtual machines, it should stop acting as if it knows what the
> > whole machine looks like.
> >
> > Paolo
>
> If guest driver can be fixed that seems ideal.
> I don't know how it works but presumably you guys do?

Paolo prefer we need to fix this in the driver like:

"
>>> The right way could be to make QEMU add a vendor-specific capability to
>>> the video device. The driver can probe for that capability before
>>
>> Do you mean we can pick two unused offsets in the configuration space of
>> the video device as a vendor-specific capability to hold the
>> vendor/device ids of the PCH?
>
> Yes, either that or add a new capability (which lets you choose the
> offsets more freely).
>
> If the IGD driver needs config space fields of the MCH, those fields
> could also be mirrored in the new capability.  QEMU would forward them
> automatically.
>
> It could even be a new BAR, which gives even more freedom to allocate
> the fields.
"

Thanks
Tiejun