NAME

       mlx5dv_qp_cancel_posted_send_wrs  -  Cancel  all pending send work requests with supplied WRID in a QP in
       SQD state

SYNOPSIS

              #include <infiniband/mlx5dv.h>

              int mlx5dv_qp_cancel_posted_send_wrs(struct mlx5dv_qp_ex *mqp, uint64_t wr_id);

DESCRIPTION

       The canceled work requests are replaced with NOPs (no operation), and will generate good completions  ac‐
       cording  to the signaling originally requested in the send flags, or “flushed” completions in case the QP
       goes to error.  A work request can only be canceled when the QP is in SQD state.

       The cancel function is a part of the signature pipelining feature.  The feature allows posting  a  signa‐
       ture  related  transfer operation together with a SEND with a good response to the client.  Normally, the
       application must wait for the transfer to end, check the MKEY for errors, and only then send  a  good  or
       bad response.  However this increases the latency of the good flow of a transaction.

       To  enable  this  feature,  a  QP must be created with the MLX5DV_QP_CREATE_SIG_PIPELINING creation flag.
       Such  QP  will  stop  after  a  transfer  operation  that  failed  signature  validation  in  SQD  state.
       IBV_EVENT_SQ_DRAINED is generated to inform about the new state.

       The  SEND operation that might need to be canceled due to a bad signature of a previous operation must be
       posted with the IBV_SEND_FENCE option in ibv_qp_ex->wr_flags field.

       When QP stopped at SQD, it means that at least one WR caused signature error.  It may not be the last WR.
       It may be that more than one WRs cause signature errors by the time the QP finally stopped.  It is  guar‐
       anteed that the QP has stopped somewhere between the WQE that generated the signature error, and the next
       WQE that has IBV_SEND_FENCE on it.

       Software must handle the SQD event as described below:

       1. Poll  everything  (polling  until 0 once) on the respective CQ, allowing the discovery of all possible
          signature errors.

       2. Look through all “open” transactions, check related signature MKEYs using  mlx5dv_mkey_check(3),  find
          the one with the signature error, get a WRID from the operation software context and handle the failed
          operation.

       3. Cancel the SEND WR by the WRID using mlx5dv_qp_cancel_posted_send_wrs().

       4. Modify the QP back to RTS state.

ARGUMENTS

       mqp    The QP to investigate, which must be in SQD state.

       wr_id  The WRID to cancel.

RETURN VALUE

       Number of work requests that were canceled, or -errno on error.

NOTES

       A DEVX context should be opened by using mlx5dv_open_device(3).

       Must be called with a QP in SQD state.

       QP  should  be created with MLX5DV_QP_CREATE_SIG_PIPELINING creation flag.  Application must listen on QP
       events, and expect a SQD event.

SEE ALSO

       mlx5dv_mkey_check(3),    mlx5dv_wr_mkey_configure(3),    mlx5dv_wr_set_mkey_sig_block(3),     mlx5dv_cre‐
       ate_mkey(3), mlx5dv_destroy_mkey(3)

AUTHORS

       Oren Duer <oren@nvidia.com>

       Sergey Gorenko <sergeygo@nvidia.com>

                                                                             mlx5dv_qp_cancel_posted_send_wrs(3)