Re: [PATCH 2/2] drm/i915: Reject an attempt to create a GGTT vma larger than the GTT

From: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 2/2] drm/i915: Reject an attempt to create a GGTT vma larger than the GTT
Date: Thu, 19 Jan 2017 15:18:03 +0200	[thread overview]
Message-ID: <1484831883.3275.7.camel@linux.intel.com> (raw)
In-Reply-To: <20170119125847.28917-2-chris@chris-wilson.co.uk>

On to, 2017-01-19 at 12:58 +0000, Chris Wilson wrote:
> For accessing large objects through the global GTT we enforce the use of
> partial views, and sanity check that the vma->size doesn't overflow and
> fits within the address space. To prevent 4GiB triggering the assert,
> catch the attempt to create the full sized vma early.
> 
> Testcase: igt/gem_exec_reloc/gtt-32
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

<SNIP>

> @@ -3679,6 +3679,12 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
>  
>  	lockdep_assert_held(&obj->base.dev->struct_mutex);
>  
> +	/* Disallow a single VMA to occupy the entire GGTT, and catch any
> +	 * attempt to create a normal VMA larger than the GGTT.
> +	 */
> +	if (!view && obj->base.size >= vm->total)
> +		return ERR_PTR(-ENOSPC);

Too sloppy. How many bytes less than the full size are OK?

Change the test to be > vm->total and then it's better.

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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