Re: [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

[Jason Gunthorpe]

On Mon, Jun 21, 2021 at 03:02:10PM +0200, Greg KH wrote:
> On Mon, Jun 21, 2021 at 02:28:48PM +0200, Daniel Vetter wrote:

> > Also I'm wondering which is the other driver that we share buffers
> > with. The gaudi stuff doesn't have real struct pages as backing
> > storage, it only fills out the dma_addr_t. That tends to blow up with
> > other drivers, and the only place where this is guaranteed to work is
> > if you have a dynamic importer which sets the allow_peer2peer flag.
> > Adding maintainers from other subsystems who might want to chime in
> > here. So even aside of the big question as-is this is broken.
> 
> From what I can tell this driver is sending the buffers to other
> instances of the same hardware,

A dmabuf is consumed by something else in the kernel calling
dma_buf_map_attachment() on the FD.

What is the other side of this? I don't see any
dma_buf_map_attachment() calls in drivers/misc, or added in this patch
set.

AFAIK the only viable in-tree other side is in mlx5 (look in
umem_dmabuf.c)

Though as we already talked habana has their own networking (out of
tree, presumably) so I suspect this is really to support some out of
tree stuff??

Jason