[openstack-dev] vGPUs support for Nova - Implementation

Bob Ball bob.ball at citrix.com
Fri Sep 29 12:26:07 UTC 2017

Hi Sahid,

> Please consider the support of MDEV for the /pci framework which provides support for vGPUs [0].

From my understanding, this MDEV implementation for vGPU would be entirely specific to libvirt, is that correct?

XenServer's implementation for vGPU is based on a pooled device model (as described in http://lists.openstack.org/pipermail/openstack-dev/2017-September/122702.html) and directly interfaces with the card using DEMU ("Discrete EMU") as a second device emulator along-side QEMU.  There is no mdev integration.  I'm concerned about how much mdev-specific functionality would have to be faked up in the XenServer-specific driver for vGPU to be used in this way.

I'm not familiar with mdev, but it looks Linux specific, so would not be usable by Hyper-V?
I've also not been able to find suggestions that VMWare can make use of mdev, although I don't know the architecture of VMWare's integration.

The concepts of PCI and SR-IOV are, of course, generic, but I think out of principal we should avoid a hypervisor-specific integration for vGPU (indeed Citrix has been clear from the beginning that the vGPU integration we are proposing is intentionally hypervisor agnostic)
I also think there is value in exposing vGPU in a generic way, irrespective of the underlying implementation (whether it is DEMU, mdev, SR-IOV or whatever approach Hyper-V/VMWare use).

It's quite difficult for me to see how this will work for other hypervisors.  Do you also have a draft alternate spec where more details can be discussed?


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