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

[Christian König]

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.

Thanks, going to take a look.
Christian.