[Intel-gfx] [PATCH 03/19] drm/i915: Micro-optimise gen8_ppgtt_insert_entries()

[Tvrtko Ursulin]

On 02/02/2017 16:10, Chris Wilson wrote:
> On Thu, Feb 02, 2017 at 03:57:43PM +0000, Tvrtko Ursulin wrote:
>>
>> On 02/02/2017 15:32, Chris Wilson wrote:
>>> On Thu, Feb 02, 2017 at 03:02:32PM +0000, Chris Wilson wrote:
>>>> Improve the sg iteration and in hte process eliminate a bug in
>>>> miscomputing the pml4 length as orig_nents<<PAGE_SHIFT is no longer the
>>>> full length of the sg table.
>>>>
>>>
>>> which fixes a corner case of 0c40ce130e38
>>> Fixes: 0c40ce130e38 ("drm/i915: Trim the object sg table")
>>
>> What do you mean? oring_nents is definitely the full length of the
>> sg table, especially after i915_sg_trim. Before it orig_nents was
>> often larger than the real length of the sg table.
>
> The code is using orig_nents as obj->base.size/vma->size (a page count,
> not the sg count), if I read it correctly as it is computing the address
> range.

Oh right, I was misled by the commit message ("is not longer the full 
length of the sg table"). Nasty. That means it was broken for userptr 
objects as well.

Regards,

Tvrtko