[2/2] drm/ttm: make TT creation purely optional v3

[Christian König]

Am 06.08.20 um 10:01 schrieb Michel Dänzer:
> On 2020-08-06 9:13 a.m., Christian König wrote:
>> Am 05.08.20 um 18:16 schrieb Michel Dänzer:
>>> On 2020-06-29 5:19 p.m., Christian König wrote:
>>>> We only need the page array when the BO is about to be accessed.
>>>>
>>>> So not only populate, but also create it on demand.
>>>>
>>>> v2: move NULL check into ttm_tt_create()
>>>> v3: fix the occurrence in ttm_bo_kmap_ttm as well
>>> This broke amdgpu userptr functionality for me, in particular all
>>> GL_AMD_pinned_memory piglit tests, e.g.
>>>
>>> .../piglit/bin/amd_pinned_memory decrement-offset -auto -fbo
>>> Offset is decremented, no wait.
>>> Mesa: User error: GL_INVALID_OPERATION in glBufferData
>>> [...]
>>> Unexpected GL error: GL_INVALID_OPERATION 0x502
>>> (Error at tests/spec/amd_pinned_memory/test.c:214)
>>> PIGLIT: {"result": "fail" }
>> But no crashes? I would have expected a NULL pointer deref if we have
>> missed call path.
> No crashes. Since a GL error is raised, my guess would be that an ioctl
> which was previously succeeding is now returning an error.

Mhm, I can reproduce the problem that userptrs doesn't work any more. 
But even with the mentioned patch reverted that still doesn't work on 
the tip of drm-misc-next.

Are you sure your bisecting is right? Going to keep testing.

Christian.