On Tue, Jul 06, 2021 at 12:44:49PM +0300, Oded Gabbay wrote:

...

...

• /* In case we got a large memory area to export, we need to divide it
  

•  * to smaller areas because each entry in the dmabuf sgt can only
  

•  * describe unsigned int.
  

•  */
  

Huh? This is forming a SGL, it should follow the SGL rules which means you have to fragment based on the dma_get_max_seg_size() of the importer device.

hmm I don't see anyone in drm checking this value (and using it) when creating the SGL when exporting dmabuf. (e.g. amdgpu_vram_mgr_alloc_sgt)

For dmabuf the only importer is RDMA and it doesn't care, but you certainly should not introduce a hardwired constant instead of using the correct function.

Jason