Hi Rob,
 thanks for the clarification. I googled a little bit and found the
"other-config:pci" option but I guess I probably need GPU passthrough,
however we'll try that.

Actually we have single NVIDIA K2 card which carries 2 GPUs so they are
correctly seen as a gpu-group of 2. We would like to attach the whole card
(i.e. 2 PCI devices) to a single VM. The VM OS is Linux (CentOS 6 64bit).

The reason for having both GPUs on the same VM is a little complicated to
explain.

We make a software which receives graphic rendering requests from the
network and passes them to the available GPUs. We have a simple GPU
load-balancer to take advantage of multiple GPUs on the same machine.
When switching from physical machines to virtual machines we can just
attach a single GPU to a VM and so we need multiple VMs to be able to use
multiple GPUs. This increases complexity and we cannot leverage our
load-balancing logic across multiple machines at the moment.

Do you know if there are some serious architectural/technical reasons
making this support very difficult to achieve or this is a limitation which
could be removed with a limited effort?

Thanks,
Andrea

On Thu, Jul 11, 2013 at 6:08 PM, Rob Hoes <[email protected]> wrote:

>  Hi Andrea,****
>
> ** **
>
> You are right: the feature is currently restricted to a single GPU per VM.
> You could try manually passing through the PCI devices of multiple GPUs
> using “other-config:pci”.****
>
> ** **
>
> I don’t think there are any plans to change this at the moment. Could you
> explain why passing through multiple GPUs to a single VM would be useful
> for you?****
>
> ** **
>
> Cheers,
> Rob****
>
> ** **
>
> *From:* [email protected] [mailto:
> [email protected]] *On Behalf Of *Andrea Curtoni
> *Sent:* 11 July 2013 4:36 PM
> *To:* [email protected]
> *Subject:* [Xen-API] GPU passthrough: multiple vGPUs on the same VM****
>
> ** **
>
> Hello,****
>
>  it looks like it is currently not possible to attach multiple vGPUs to
> the same VM. I tried with XenServer 6.2 and suspect the same happens with
> XCP 1.6.****
>
> ** **
>
> I'm successfully using an NVIDIA card in GPU passthrough from a VM but
> when I try to attach a second vGPU I get the following error:****
>
> ** **
>
> [root@xenserver ~]# xe vgpu-create vm-uuid=... gpu-group-uuid=...****
>
> A device with the name given already exists on the selected VM****
>
> device: 0****
>
> ** **
>
> Trying to specify a different device did not help:****
>
> ** **
>
> [root@xenserver ~]# xe vgpu-create vm-uuid=... gpu-group-uuid=... device=1
> ****
>
> The device name is invalid****
>
> device: 1****
>
> ** **
>
> I think the support for multiple vGPUs on a single VM is not implemented
> at the moment, I'd like to understand the following:****
>
> 1) is it possible to workaround this limitation?****
>
> 2) are there any plans to introduce this support in the future?****
>
> ** **
>
> Thanks in advance,****
>
> Andrea****
>



-- 
Andrea Curtoni
NICE srl
[email protected]
http://www.nice-software.com/
www.enginframe.com
TEL: +39 0141 90.15.16
FAX: +39 0141 01.98.29
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