[Intel-gfx] [PATCH] drm/i915/guc: Document that the ads blob entries only lie within the first page

[Chris Wilson]

On Thu, Mar 16, 2017 at 12:06:20PM +0100, Michal Wajdeczko wrote:
> On Thu, Mar 16, 2017 at 10:58:20AM +0000, Chris Wilson wrote:
> > On Thu, Mar 16, 2017 at 10:55:06AM +0000, Chris Wilson wrote:
> > > guc_addon_create() makes the assumption that it need only kmap the
> > > initial page in order to write all of the configuration data used by the
> > > guc. Confusingly it also allocates many scratch pages in the same vma
> > > and passes that to the guc. Reassure the reader that all is well with a
> > > BUILD_BUG_ON() that we do not access outside of the kmapped page.
> > > 
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> > > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > > Cc: Oscar Mateo <oscar.mateo at intel.com>
> > > Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_guc_submission.c | 5 +++++
> > >  drivers/gpu/drm/i915/i915_utils.h          | 1 +
> > >  2 files changed, 6 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> > > index 97726fcb1230..91d7ab0df0cd 100644
> > > --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> > > +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> > > @@ -888,13 +888,16 @@ static void guc_addon_create(struct intel_guc *guc)
> > >  		guc->ads_vma = vma;
> > >  	}
> > >  
> > > +	/* First members are assumed to be in a single page */
> > 
> > s/First/Written/
> 
> Btw, maybe it would be better to move all these BUILD_BUGs here?

I was thinking next to the write so that if they were changed, copied,
it would be more obvious to update; as well as the check being clearly
associated with the write.
-Chris


-- 
Chris Wilson, Intel Open Source Technology Centre