[Intel-gfx] [PATCH 2/3] drm/i915/gvt: Return -EIO if host enable_execlists not enabled when loading GVT-g

[Dong, Chuanxiao]

> -----Original Message-----
> From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> Sent: Friday, May 26, 2017 5:35 PM
> To: Dong, Chuanxiao <chuanxiao.dong at intel.com>
> Cc: intel-gvt-dev at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH 2/3] drm/i915/gvt: Return -EIO if host
> enable_execlists not enabled when loading GVT-g
> 
> On Fri, May 26, 2017 at 11:04:18AM +0800, Chuanxiao Dong wrote:
> > GVT-g relies on the enable_execlists parameter in i915. If this option
> > is not enabled for GVT-g, should return -EIO to make i915 driver
> > loading failed.
> >
> > Suggested-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Signed-off-by: Chuanxiao Dong <chuanxiao.dong at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_gvt.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_gvt.c
> > b/drivers/gpu/drm/i915/intel_gvt.c
> > index dde9c78..c90d476 100644
> > --- a/drivers/gpu/drm/i915/intel_gvt.c
> > +++ b/drivers/gpu/drm/i915/intel_gvt.c
> > @@ -97,7 +97,7 @@ int intel_gvt_init(struct drm_i915_private
> > *dev_priv)
> >
> >  	if (!i915.enable_execlists) {
> >  		DRM_INFO("GPU guest virtualisation [GVT-g] disabled due to
> disabled execlist submission [i915.enable_execlists module parameter]\n");
> > -		goto bail;
> > +		return -EIO;
> 
> Hmm, interesting debate as to whether or not you still want to set
> i915.enable_gvt=0 to indicate gvt being lost. Since this will cause the driver
> to fail to load, it should be now DRM_ERROR("and the error message
> changed to reflect the fatal failure!") and having modprobe report -EIO with
> i915.enable_gvt still to 1 seems like the best approach.
> -Chris

Yes, agree with keeping i915.enable_gvt to be 1, this is also the current solution. For the error message, how about DRM_ERROR("i915 GVT-g driver loading failed due to disabled execlists mode.\n")?

Regarding fail with -EIO, as we can take i915.enable_gvt as a single feature of intel i915 GPU, is it still reasonable to return -EIO to disable the whole i915 driver? It is something like two features A and B in i915, as B relies on A, so B should be disabled if detected feature A is not enable, but not just making the whole i915 stack disabled.

Thanks
Chuanxiao