Re: [PATCH 3/7] drm/i915: Always enable execlists on BDW for vgpu

Chris Wilson
2015-08-20T09:22:45Z

On Thu, Aug 20, 2015 at 04:55:08PM +0800, Zhiyuan Lv wrote:
> Hi Chris,
>
> On Thu, Aug 20, 2015 at 09:34:05AM +0100, Chris Wilson wrote:
> > On Thu, Aug 20, 2015 at 03:45:20PM +0800, Zhiyuan Lv wrote:
> > > Broadwell hardware supports both ring buffer mode and execlist mode.
> > > When i915 runs inside a VM with Intel GVT-g, we allow execlist mode
> > > only. The reason is that GVT-g does not support the dynamic mode
> > > switch between ring buffer mode and execlist mode when running
> > > multiple virtual machines. Consider that ring buffer mode is legacy
> > > mode, it makes sense to drop it inside virtual machines.
> >
> > If that is the case, you should query the host as to what mode it is
> > running.
>
> Thanks for the reply! You mean we query the host mode, then tell the
> guest driver inside VM, so that it could use the same mode as host
> right? That might be a little complicated, and the only benefit is to
> support legacy ring buffer mode ...

The only benefit being that the guest works no matter what the host
does?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre