amdgpu_ttm_tt_get_user_pages
r = amdgpu_ttm_tt_get_user_pages(ttm, e->user_pages);
r = amdgpu_ttm_tt_get_user_pages(bo->tbo.ttm,
int amdgpu_ttm_tt_get_user_pages(struct ttm_tt *ttm, struct page **pages);