IB/rxe: Add support for zero-byte operations

The last_psn algorithm fails in the zero-byte case: it calculates
first_psn = N, last_psn = N-1. This makes the operation unretryable since
the res structure will fail the (first_psn <= psn <= last_psn) test in
find_resource().

While here, use BTH_PSN_MASK to mask the calculated last_psn.

Signed-off-by: Andrew Boyer <andrew.boyer@dell.com>
Reviewed-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

2 files changed, 18 insertions, 3 deletions

diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
index 1869152f1d23..d0faca294006 100644
--- a/drivers/infiniband/sw/rxe/rxe_mr.c
+++ b/drivers/infiniband/sw/rxe/rxe_mr.c
@@ -355,6 +355,9 @@ int rxe_mem_copy(struct rxe_mem *mem, u64 iova, void *addr, int length,
         size_t                  offset;
         u32                     crc = crcp ? (*crcp) : 0;
 
+        if (length == 0)
+                return 0;
+
         if (mem->type == RXE_MEM_TYPE_DMA) {
                 u8 *src, *dest;
 
diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
index cb3fd4cb0daa..a5e9ce34171b 100644
--- a/drivers/infiniband/sw/rxe/rxe_resp.c
+++ b/drivers/infiniband/sw/rxe/rxe_resp.c
@@ -444,6 +444,13 @@ static enum resp_states check_rkey(struct rxe_qp *qp,
                 return RESPST_EXECUTE;
         }
 
+        /* A zero-byte op is not required to set an addr or rkey. */
+        if ((pkt->mask & (RXE_READ_MASK | RXE_WRITE_OR_SEND)) &&
+            (pkt->mask & RXE_RETH_MASK) &&
+            reth_len(pkt) == 0) {
+                return RESPST_EXECUTE;
+        }
+
         va      = qp->resp.va;
         rkey    = qp->resp.rkey;
         resid   = qp->resp.resid;
@@ -680,9 +687,14 @@ static enum resp_states read_reply(struct rxe_qp *qp,
                 res->read.va_org        = qp->resp.va;
 
                 res->first_psn          = req_pkt->psn;
-                res->last_psn           = req_pkt->psn +
-                                          (reth_len(req_pkt) + mtu - 1) /
-                                          mtu - 1;
+
+                if (reth_len(req_pkt)) {
+                        res->last_psn   = (req_pkt->psn +
+                                           (reth_len(req_pkt) + mtu - 1) /
+                                           mtu - 1) & BTH_PSN_MASK;
+                } else {
+                        res->last_psn   = res->first_psn;
+                }
                 res->cur_psn            = req_pkt->psn;
 
                 res->read.resid         = qp->resp.resid;