Re: [Xen-devel] GPU passthrough on ARM

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi,

I am CCing Oleksandr. He knows better than me this platform.

Cheers,

On 26/01/18 00:29, Martin Kelly wrote:
> On 01/25/2018 04:17 AM, Julien Grall wrote:
> > On 24/01/18 22:10, Martin Kelly wrote:
> > > Hi,
> > Hello,
> >
> > > Does anyone know if GPU passthrough is supported on ARM? (e.g. for a 
> > > GPU integrated into an ARM SoC). I checked documentation and the 
> > > code, but I couldn't tell for sure.
> > > If so, what are the hardware requirements for it? If not, is it 
> > > feasible to do in the future?
> > Xen Arm supports device integrated into an ARM SoC. In general we 
> > highly recommend to have the GPU behind an IOMMU. So passthrough would 
> > be fully secure.
> > Does your platform has an IOMMU? If so which one? Do you know if the 
> > GPU is behind it?
> > It would be possible to do passthrough without IOMMU, but that's more 
> > complex and would require some hack in Xen to make sure the guest 
> > memory is direct mapped (e.g guest physical address = host physical 
> > address).
> > For more documentation on how to do it (see [1] and [2]).
> >
> > Cheers,
> >
> > [1] 
> > https://events.static.linuxfound.org/sites/events/files/slides/talk_5.pdf
> > [2] https://wiki.xen.org/images/1/17/Device_passthrough_xen.pdf
> Hi Julien,
>
> Thanks very much for the information. I'm looking at the Renesas R-Car 
> H3 R8A7795, which has an IOMMU (using the Linux ipmmu-vmsa driver in 
> drivers/iommu/ipmmu-vmsa.c). Looking at the device tree for it 
> (r8a7795.dtsi), it appears you could pass through the display@feb00000 
> node for the DRM driver.
> I did notice this patch series, which didn't get merged:
>
> https://lists.xenproject.org/archives/html/xen-devel/2017-07/msg02679.html
>
> Presumably that driver would be needed in Xen.
>
> Are there any gotchas I'm missing? Is GPU passthrough on ARM something 
> that is "theoretically doable" or something that has been done already 
> and shown to be performant?
> Thanks again,
> Martin
--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel