Re: [PATCH v4 2/2] habanalabs: add support for dma-buf exporter

Jason Gunthorpe
2021-07-06T15:13:00Z

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