Re: [PATCH] rxe: Fix dma.length computation in wr_set_sge_list

[Jason Gunthorpe <jgg@nvidia.com>]

On Sun, May 31, 2026 at 03:07:21PM +0300, Jared Holzman wrote:
> wr_set_sge_list() summed the SGE lengths with a loop that never
> advanced sg_list:
> 
> 	while (num_sge--)
> 		tot_length += sg_list->length;
> 
> so tot_length ended up as num_sge * sg_list[0].length instead of the
> true sum, and wqe->dma.length / wqe->dma.resid were written with that
> wrong value. The per-SGE entries themselves were unaffected because
> they are populated by the preceding memcpy().
> 
> The kernel rxe driver requires dma.length == sum(sge[i].length) and
> enforces it in rxe_mr.c:copy_data(), so a multi-SGE WR posted through
> the ibv_qp_ex builder API (ibv_wr_set_sge_list) on rxe completes with
> IB_WC_LOC_PROT_ERR once finish_packet()/copy_data() runs off the end
> of the SGE list.
> 
> The legacy ibv_post_send path (init_send_wqe) is unaffected; it sums
> the lengths with an indexed for loop.
> 
> Fix by computing the total with an indexed loop, matching the style
> already used in rxe_post_one_recv() and init_send_wqe() in this file.
> 
> Fixes: 1a894ca10105 ("Providers/rxe: Implement ibv_create_qp_ex verb")
> Signed-off-by: Jared Holzman <jholzman@nvidia.com>
> PR: https://github.com/linux-rdma/rdma-core/pull/1744

I don't know what this is, upstream doesn't have this code qp_ex
support or 1a894ca10105

The rdma-core thing looks OK though.

Jason