Re: [PATCH for-next] RDMA/efa: Add CQ with external memory support

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Jun 09, 2025 at 06:03:32PM +0300, Margolin, Michael wrote:
> 
> On 5/26/2025 7:17 PM, Margolin, Michael wrote:
> > 
> > On 5/26/2025 7:08 PM, Jason Gunthorpe wrote:
> > > On Mon, May 26, 2025 at 06:45:59PM +0300, Margolin, Michael wrote:
> > > 
> > > > Are you suggesting turning mlx5dv_devx_umem_reg into a common
> > > > verb including
> > > > the kernel part or some kind of rdma-core level abstraction for passing
> > > > dmabuf+offset+length / address+length to a create CQ/QP function?
> > > I think Leon was, but I'm not sure that is so worthwhile.
> > > 
> > > I was thinking more of having the ioctls for things like QP/CQ/MR
> > > accept a more standard common set of attributes to describe the buffer
> > > memory and then making it simpler for the driver to get a umem from
> > > those common attributes.
> > > 
> > > But EFA is alread sort of different because it normally uses a kernel
> > > allocated buffer, right?
> > > 
> > > Jason
> > 
> > Yes, EFA is an example for a driver that doesn't need this on the
> > "standard" flow.
> > 
> > Michael
> > 
> How can we move forward with this patch? It's possible to add additional
> attributes to the common create CQ ioctl and use it for EFA direct verbs but
> it won't be easy to move existing drivers to use it.

Then it becomes hard to make the other drivers reject those new common
attributes :\

Maybe what you have here is the best, but it really does seem
unsatisfying from a kernel POV..

Jason