Re: [Xen-users] CUDA compatibility with XEN

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 2014-07-18 16:12, Daniele Tartarini wrote:
> Dear all,
>
> I would like to use Nvidia CUDA for GPGPU on virtualised machines.
> I made a test using ubuntu 14.04 that works perfectly with even the
> CUDA RC 6.5.
>
> When I installed Xen I was not able any more to run CUDA (I get access
> to GPU hardware info but I cannot run the more simple code: "error
> code 46 cudaErrorDevicesUnavailable").
>
> I would like to know whether is there any solution that allows to use
> CUDA on Xen Dom0 or on the other domain/VMs.
There is a known issue that causes this in dom0. I'm sure I saw a
patch to fix that floating around, google it, I'm sure you'll
find it, but you'll have to patch and rebuild Xen from sources.

This issue doesn't occur in domU, but the only way to run an Nvidia
card in domU is if you have one of the Quadro, Grid or Tesla cards
that Nvidia will let you use in a virtualized environment (the
permitted cards have their PCI device IDs hard-coded in the driver).

You can only work around this by:

1) Modifying the card (BIOS modification on cards up to and
including the GTX480, hardware modification on later models) to
alter the device ID it exposes.

2) Doctoring the Nvidia binary driver to neuter the device ID
check (disassembling of the driver and subsequent modification is
required, which will void your EULA for using the driver).

For the driver modification you're on your own. The card
modifications, OTOH, are well documented.

If you want to run cuda in dom0, then you should be able to
achieve that with the above mentioned Xen patch.

Note that the latest Nvidia driver that works in dom0 appears to
be 319.82. Later versions crash when starting Xorg. 319.82
works unmodified up to kernel version 3.12. For later kernels
you will have to patch it (I have patched versions for running
with kernels 3.13 and 3.14).

Gordan

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