Re: [Xen-devel] GTX 760 passed through

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Dec 02, 2013 at 09:04:51PM +0000, Gordan Bobic wrote:
> On 12/02/2013 08:16 PM, Konrad Rzeszutek Wilk wrote:
> >On Mon, Dec 02, 2013 at 06:36:48PM +0100, Nvidia Reverse wrote:
> >>The nvlddmkm.sys needs to be patched removing the whitelist for the device
> >>ids allowed to be virtualized.
> >>But the interesting part is how NVIDIA detects that the GPU is
> >>virtualized...
> >
> >Interesting. I was thinking that the BIOS/firmware would run itself
> >in the virtualized or non-virtualized code depending on the device id.
> >But you seem to imply that it is all in the OS driver code.
> 
> Certainly not the case with the BIOS part - Quadro BIOS is quite
> different. GeForce BIOS, for example, doesn't have ECC control code
> and a few other things. For example, flash a 4GB GTX680 with a K5000
> BIOS and the ECC control options start to show up in the control
> panel. If they went to the trouble of stripping all that out of the
> GeForce BIOS I'd rather like to think that they would have tripped
> out any magic required to run virtualized.
> 
> Since we know that isn't the case (since removing a single resistor
> on a 680 makes it work just fine virtualized as a Tesla K10), the
> only logical conclusion there is nothing that the BIOS does that
> makes any difference to virtualization.
> 
> >At which point the idea of just modifying in QEMU the PCI device ID
> >to be different would .. well, make it possible to do a lot of
> >neat stuff as Gordan pointed out.
> 
> Only on pre-Kepler GPUs. As far as I can tell, there is a register
> in the GPU where the hard-strapped device ID is kept, and this gets
> set at boot time BEFORE the BIOS runs. It is the pre-BIOS device ID
> that gets stuck in the GPU, and the soft-strap only affects the PCI
> device ID - yes, the two can differ on Kepler. Driver keys off the

HA! Schizophrenic card.

> hard-strapped ID.
> 
> >In terms of legal issues of patching up a windows kernel driver and
> >showing other folks how to do it?
> >
> >No idea. Presumarily there is some license thing that you had agreed
> >when you installed the Nvidia driver - check to see what it says.
> 
> I think the OP was more referring to specifically applying a patch
> to Xen to prevent the Nvidia driver in domU from being able to
> figure out it's running in a VM. If it doesn't think it's running in
> a VM, it doesn't disable the device.

Oh, Xen is open-source so you can do whatever you want (to a certain
extent of course - you can't package and resell it without providing
a means to get the source code).
> 
> BTW, Konrad, did your GTX460 work with PCI passthrough after
> modifying it to a Q4000M?

Yes, pretty fantastic! And it seems to work OK - I am loading some
games on the Windows guest to double-check. The audio part does not
seem to work - oddly enough.

I also have a Radeon 4870  that in the past worked when passing
in the guest but one had to 'unplug' it in Windows to be able to
restart it again. Will try that once I get a machine that can have
three GPUs in it.

Now I hadn't tried to start the Windows guest with more than 2GB -
but when I do that I should have some patches to make that work (based
on your work).


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