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

From: Chris Wilson <chris@chris-wilson.co.uk>
To: intel-gfx@lists.freedesktop.org, igvt-g@lists.01.org
Subject: Re: [PATCH 3/7] drm/i915: Always enable execlists on BDW for vgpu
Date: Thu, 20 Aug 2015 10:22:37 +0100	[thread overview]
Message-ID: <20150820092237.GR8742@nuc-i3427.alporthouse.com> (raw)
In-Reply-To: <20150820085508.GC3226@zlv-hp-dev>

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
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