[Xen-users] vGPU support and other GPU passthru (Re: [qubes-users] Qubes 4 Release Date)

[sm8ax1 <sm8ax1@xxxxxxxxxxx>]

(CCing xen-users - please reply all but be careful not to
cross-contaminate lists with off-topic stuff)

lokedhs@xxxxxxxxx:
> On Wednesday, 8 March 2017 02:59:18 UTC+8, cooloutac  wrote:
>> I think most new users want more passthrough like gpu. IMO if I want to be 
>> secure 
>> on my pc i try to avoid those things.  I have a separate machine for gaming 
>> for 
>> example.  But I guess the idea of qubes is to be able to do risky things 
>> more 
>> securely in isolated manner and is originally aimed at home users.
> 
> Didn't the Linux kernel gain VGPU support recently? The whole point of that 
> feature is to allow VM's to take advantage of the GPU. Couldn't that be 
> supported in Qubes?
> 

I don't know anything about this, but from a quick search it sounds like
vGPU is only supported on machines running Citrix XenDesktop with a
supported nVidia (GRID K1 or K2) cards. Even if it is supported by
vanilla Xen, I don't think it works on ATI or Intel GPUs, but I could be
wrong. If anyone knows more about this please share.

https://www.nvidia.com/object/xendesktop-vgpu.html
https://www.nvidia.com/object/grid-technology.html
https://cwiki.apache.org/confluence/display/CLOUDSTACK/GPU+and+vGPU+support+for+CloudStack+Guest+VMs
https://gridforums.nvidia.com/default/topic/479/general-discussion/vgpu-support-/

There is also virtio-gpu, which is a virtual, hardware-independent GPU
driver supported by KVM. It's in active development and has been covered
by a lot of sources, so I assume it's becoming pretty reliable. As far
as I can tell, it is only meant to work with SPICE, but in theory could
outperform the software rendering we're doing now. It appears to be
supported by Xen (at least HVMs) via QEMU. I think the QXL driver is
similar.

https://www.kraxel.org/blog/tag/virtio-gpu/
https://lists.gt.net/xen/devel/406512

In theory I suppose Qubes could one day replace its existing
software-rendering with SPICE and virtio-gpu or QXL, but it's not clear
if it would result in any significant performance gain (i.e. if SPICE's
network protocol and virtio-gpu/qxl-to-native rendering would actually
be faster than software rendering over a vchan).

GPU passthru is something that comes up on the Xen mailing list fairly
regularly, but getting it to work is very hit-or-miss. I've tried it
with several Intel HD series GPUs and have never been able to make it
work personally.

https://wiki.xen.org/wiki/Xen_PCI_Passthrough
https://wiki.xenproject.org/wiki/Xen_VGA_Passthrough
https://wiki.xenproject.org/wiki/Xen_VGA_Passthrough_Tested_Adapters

Even if you passthru the GPU, however, it won't passthru the PS/2 mouse
and keyboard, although that would probably be easy to work around (like
Qubes already does).

And of course the long-awaited XenGT is an idea to build virtualization
support into Intel GPU hardware. It would allow the GPU to be passed
through to multiple VMs at a time, for direct rendering/acceleration of
multiple windows. I call it an idea because it's several years in the
making and as far as I know it's still not mainlined, hasn't received a
commit since January 2015, and still no GPUs actually support it.

https://wiki.xenproject.org/wiki/XenGT
https://blog.xenproject.org/2014/03/11/xen-graphics-virtualization-xengt/
https://01.org/xen/blogs/srclarkx/2013/graphics-virtualization-xengt

For the sake of completeness, paravirtualized DRM was arguably perhaps
our best approach for accelerated graphics, at least on Linux, but it
appears to have been abandoned.

https://wiki.xen.org/wiki/Paravirtualized_DRM

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