Re: [PATCH for-next] RDMA/rxe fixed bug in rxe_requester

[Leon Romanovsky <leon@kernel.org>]

On Tue, Oct 13, 2020 at 12:07:42PM -0500, Bob Pearson wrote:
> The code which limited the number of unacknowledged PSNs was incorrect.
> The PSNs are limited to 24 bits and wrap back to zero from 0x00ffffff.
> The test was computing a 32 bit value which wraps at 32 bits so that
> qp->req.psn can appear smaller than the limit when it is actually larger.
>
> Replace '>' test with psn_compare which is used for other PSN comparisons
> and correctly handles the 24 bit size.
>
> Fixes: 8700e3e7c485 ("Soft RoCE (RXE) - The software RoCE driver")
> Signed-off-by: Bob Pearson <rpearson@hpe.com>
> ---
>  drivers/infiniband/sw/rxe/rxe_req.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_req.c b/drivers/infiniband/sw/rxe/rxe_req.c
> index af3923bf0a36..d4917646641a 100644
> --- a/drivers/infiniband/sw/rxe/rxe_req.c
> +++ b/drivers/infiniband/sw/rxe/rxe_req.c
> @@ -634,7 +634,8 @@ int rxe_requester(void *arg)
>  	}
>
>  	if (unlikely(qp_type(qp) == IB_QPT_RC &&
> -		     qp->req.psn > (qp->comp.psn + RXE_MAX_UNACKED_PSNS))) {
> +		psn_compare(qp->req.psn, (qp->comp.psn +
> +				RXE_MAX_UNACKED_PSNS)) > 0)) {

qp->comp.psn is u32, so you are checking that
qp->comp.psn + RXE_MAX_UNACKED_PSNS != 0, am I right?

>  		qp->req.wait_psn = 1;
>  		goto exit;
>  	}
> --
> 2.25.1
>