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Re: [Xen-devel] Nvidia GPU passthrough and Device IDs

On 28/11/13 11:21, Gordan Bobic wrote:
> This has recently come to my attention:
> http://www.nvidia.com/object/user-selectable-machines.html
> along with this snippet of information:
> - Physical Function PCIid: 10ed:11bf - GK104GL [GRID K2]
> - Virtual Function selectable from
> PCIid: 10ed:118b - GK104 [GeForce K2 USM]
> PCIid: 10ed:118c - GK104 [NVS K2 USM]
> PCIid: 10ed: 11b0 - GK104GL [Quadro K2 USM]
> PCIid: 10ed:11b1 - GK104GL [Tesla K2 USM]
> The way this reads to me is that it means that a different
> device ID is exposed to domU than what runs on the host.
> Therefore, it must be possible to change the device ID
> visible to domU to something other than what is visible
> on the host.
> So, as per a question that has recently been asked, is
> there a way to apply a software shim to expose a different
> device ID to the domU when doing PCI passthrough? This
> might completely avoid the need to modify the GeForce
> cards in ways discussed here recently to make them
> work in PCI passthrough mode by simply faking the
> device ID exposed.
> Gordan

All config space accesses get vetted by Qemu or pcifront.

We have had one bug for a particular graphics card with PCI passthrough
which was fixed by faking up the wrong class code.  (There was a windows
XPDM/WDDM stack issue with the affected card, and the cirrus emulated
graphics card was detected as "better" than the passed-through one)


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