[Intel-gfx] [PATCH] drm/i915/gvt: disable GVT-g if host GuC submission is enabled

[Dong, Chuanxiao]

> -----Original Message-----
> From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> Sent: Friday, May 5, 2017 5:11 PM
> To: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Zhenyu Wang <zhenyuw at linux.intel.com>; Dong, Chuanxiao
> <chuanxiao.dong at intel.com>; Daniel Vetter <daniel.vetter at ffwll.ch>; intel-
> gfx at lists.freedesktop.org; intel-gvt-dev at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/gvt: disable GVT-g if host GuC
> submission is enabled
> 
> On Fri, May 05, 2017 at 11:55:14AM +0300, Joonas Lahtinen wrote:
> > + Daniel
> >
> > On ke, 2017-05-03 at 16:36 +0800, Zhenyu Wang wrote:
> > > On 2017.05.02 16:58:31 +0800, Chuanxiao Dong wrote:
> > > >
> > > > Currently GVT-g cannot work properly when host GuC submission is
> > > > enabled, so disable GVT in this case.
> > > >
> > > > Cc: Zhenyu Wang <zhenyuw at linux.intel.com>
> > > > Signed-off-by: Chuanxiao Dong <chuanxiao.dong at intel.com>
> >
> > <SNIP>
> >
> > > > @@ -84,6 +84,11 @@ int intel_gvt_init(struct drm_i915_private
> *dev_priv)
> > > >  		goto bail;
> > > >  	}
> > > >
> > > > +	if (i915.enable_guc_submission) {
> > > > +		DRM_INFO("GPU guest virtualisation [GVT-g] disabled due to
> > > > +enabled GuC submission [i915.enable_guc_submission module
> > > > +parameter]\n");
> >
> > Guest module parameter is not the correct way of detetecting if host
> > has GuC submission enabled. And even if it was, the message is overly
> > verbose (and it'll be incorrect once i915.enable_guc_submission
> > defaults to something else than zero).
> 
> It needs to be verbose because it is a message to the user, it should tell them
> what broke, what that will likely mean to them and if possible how to rectify.
> Even then we know they won't read the entirety of the message but at least
> it gives us a starting point for the inevitable bugs. We should always aim for
> clarity and avoid too much jargon in DRM_INFO+.
> 
> In this case, you could argue that i915.enable_guc_submission is an unsafe
> parameter set to off by default and so the combination of gvt + guc is pure
> user error and they can keep both pieces.
> 
> Ideally we wouldn't use i915.enable_guc_submission at all, but gvt should be
> disabled upon enabling guc -- since the combination is currently inoperable.
> But again, this is just a user error and we can just -EIO the driver load...
> -Chris

Hi Chris/Joonas,

Do you agree to use i915.enable_guc_submission for telling gvt to disable itself?

Thanks
Chuanxiao

> 
> --
> Chris Wilson, Intel Open Source Technology Centre