Re: [PATCH for-next 2/2] RDMA/efa: Add CQ with external memory support

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Jul 01, 2025 at 11:15:45PM +0000, Michael Margolin wrote:
> +	if (umem) {
> +		umem_sgl = ibcq->umem->sgt_append.sgt.sgl;
> +		if (sg_dma_len(umem_sgl) < ib_umem_offset(umem) + cq->size) {
> +			ibdev_dbg(&dev->ibdev, "Non contiguous CQ unsupported\n");
> +			err = -EINVAL;
> +			goto err_free_mem;
> +		}

I'd rather see this call ib_umem_find_best_pgsz()

Maybe like:
  len = ib_umem_offset(umem) + cq->size
  pgsz = roundup_pow_of_two(len);
  ib_umem_find_best_pgoff(umem, pgsz, U64_MAX);
  rdma_umem_for_each_dma_block(umem, biter, pgsz) {
       dma = rdma_block_iter_dma_address(&biter) +  ib_umem_dma_offset(umem, pgsz);
       break;
  }

It turns out the scatterlists can be irregular in some cases so this
will handle that properly while the little test above cannot.

And maybe the above thing could be a little helper:

bool ib_umem_get_contiguous_dma(umem, &dma_addr)

Also I am trying hard to keep scatterlist APIS out of the drivers.

Jason