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    Subject[PATCH 4.19 106/346] RDMA/rxe: Compute PSN windows correctly
    Date
    From: Bob Pearson <rpearsonhpe@gmail.com>

    [ Upstream commit bb3ab2979fd69db23328691cb10067861df89037 ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 1c1eae0ef8c28..63db49144f62b 100644
    --- a/drivers/infiniband/sw/rxe/rxe_req.c
    +++ b/drivers/infiniband/sw/rxe/rxe_req.c
    @@ -664,7 +664,8 @@ 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;
    }
    --
    2.27.0


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