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

[Zhang, Yang Z]

Fabio Fantoni wrote on 2014-05-19:
> Il 19/05/2014 08:44, Gerd Hoffmann ha scritto:
>>    Hi,
>>> +    /* +     * Some video bioses and gfx drivers will assume the bdf
>>> of IGD is 00:02.0. +     * So user need to set it to 00:02.0 in Xen
>>> configure file explicitly, +     * otherwise IGD will fail to work. + 
>>>    */ +    pci_reserve_pci_devfn(b, PCI_DEVFN(2, 0));
>> That is asking for trouble.  Slot 2 is used by the qemu vga cards by
>> default, and for quite a while (before memory api was merged) it even
>> was impossible to change it.  libvirt still places the vga card at slot
>> 2 for that reason -> boom.  I wouldn't be surprised if you find that
>> assumption in other management libs / apps too.
>> 
>> Why do you need that patch in the first place?  It should be possible to
>> configure qemu to not occupy slot 2 if you need it that way.  Just pass
>> '-vga none' to qemu.  Which you probably want anyway if you pass-through
>> a vga to the guest.  And explicitly configure a slot (via addr=
>> property) for all your pci devices.  Doing it only for the IGD works too
>> if you list the device before any other pci device on the qemu command
>> line.
>> 
>> cheers,
>>    Gerd
> 
> I already added vga none support on libxl, useful also for this cases:
> http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=2e5738ff47b9d2e19480
> 24100f87b1a25fcf004a

Thanks for provide such useful information to us. I will try to see whether it 
can meet our demand.

> 
> This patch is already tested and working, for now I not tested and I
> can't test with intel gpu passthrough, someone can test it with intel
> gpu passthrough?
> 
> Thanks for any reply and sorry for my bad english.
> 
>> 
>> 
>> 
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Best regards,
Yang