Re: [PATCH 3/3] drm/i915: Ignore duplicate VMA stored within the per-object handle LUT

Chris Wilson
2017-08-23T10:22:31Z

Quoting Joonas Lahtinen (2017-08-23 11:05:18)
> On Tue, 2017-08-22 at 12:05 +0100, Chris Wilson wrote:
> > By using drm_gem_flink/drm_gem_open on an object using the same fd, it
> > is possible for a client to create multiple handles pointing to the same
> > object (tied to the same contexts and VMA), as exemplified by
> > igt::gem_handle_to_libdrm_bo(). Since this duplication has been possible
> > since forever, we cannot assume that the handle:(fpriv, object) is
> > unique and so must handle the multiple users of a single VMA.
> >
> > Testcase: igt/gem_close
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102355
> > Fixes: d1b48c1e7184 ("drm/i915: Replace execbuf vma ht with an idr")
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
>
> <SNIP>
>
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -720,6 +720,7 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
> > goto err_obj;
> > }
> >
> > + vma->open_count++;
> > list_add(&lut->obj_link, &obj->lut_list);
>
> This code maybe should be in i915_gem.c as "i915_gem_object_add_lut" or
> something.

I disagree. It's very much tied to being an execbuf only interaction,
that obj/ctx/handle.
-Chris