RDMA/rxe: Compute PSN windows correctly

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 driver")
Link: https://lore.kernel.org/r/20201013170741.3590-1-rpearson@hpe.com
Signed-off-by: Bob Pearson <rpearson@hpe.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/infiniband/sw/rxe/rxe_req.c b/drivers/infiniband/sw/rxe/rxe_req.c
index af3923bf0a36bf32bbcb3d4efedcc2b6d0ffc1f1..d4917646641aad4e036defd8ed20ff9afe94e590 100644 (file)
--- a/drivers/infiniband/sw/rxe/rxe_req.c
+++ b/drivers/infiniband/sw/rxe/rxe_req.c
@@ -634,7 +634,8 @@ next_wqe:
        }
 
        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->req.wait_psn = 1;
                goto exit;
        }