[Intel-gfx] [PATCH v3] drm/i915/gvt: return the actual aperture size under gvt environment

[Li, Weinan Z]

> -----Original Message-----
> From: Joonas Lahtinen [mailto:joonas.lahtinen at linux.intel.com]
> Sent: Tuesday, May 9, 2017 8:36 PM
> To: Li, Weinan Z <weinan.z.li at intel.com>; intel-gfx at lists.freedesktop.org; intel-
> gvt-dev at lists.freedesktop.org
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Subject: Re: [PATCH v3] drm/i915/gvt: return the actual aperture size under gvt
> environment
> 
> On ti, 2017-05-09 at 03:10 +0000, Li, Weinan Z wrote:
> 
> > > > > @@ -242,6 +242,9 @@ int intel_vgt_balloon(struct
> > > > > drm_i915_private
> > > > > *dev_priv)
> > > > >  			goto err;
> > > > >  	}
> > > > >
> > > > > +	for (i = 0; i < ARRAY_SIZE(bl_info.space); i++)
> > > > > +		ggtt->base.reserved += bl_info.space[i].size;
> > > > > +
> > >
> > > There should be an equal decrease when deballooning is done. And for
> > > that to be correct, you need to add proper onion teardown to this
> > > function to make sure the count stays correct (can't call deballoon
> > > on failure or the count will become negative which will result in huge
> number marked as reserved).
> > Oh, that's my fault. Should add clean up in intel_vgt_deballoon().
> > @@ -114,6 +114,7 @@ void intel_vgt_deballoon(struct drm_i915_private
> > *dev_priv)
> >         }
> >
> >         memset(&bl_info, 0, sizeof(bl_info));
> > +       dev_priv->ggtt.reserved = 0;
> > }
> > Since if any steps in intel_vgt_balloon() fail, it will deal as error
> > and run
> > intel_vgt_deballoon() for clean up, no partial success happen.
> > So we only calculate the reserved when balloon success, it can ensure it's
> correct.
> 
> Onion teardown should be used according to kernel coding style, there's really
> no excuse not to.
> 
> Just add to the ggtt->base.reserved in increments, and remove in increments
> during teardown or in the deballoon function. ggtt.reserved is not exclusively
> for GVT-g to use, so you can't simply zero it. There needs to be incremental
> additions and substractions as objects are added and removed for the variable
> to stay general.
Got it, I will refine it and send as patch v4.
> 
> Regards, Joonas
> --
> Joonas Lahtinen
> Open Source Technology Center
> Intel Corporation