Merge branch 'ibmvnic-Bug-fixes-for-queue-descriptor-processing'

Thomas Falcon says:

====================
ibmvnic: Bug fixes for queue descriptor processing

This series resolves a few issues in the ibmvnic driver's
RX buffer and TX completion processing. The first patch
includes memory barriers to synchronize queue descriptor
reads. The second patch fixes a memory leak that could
occur if the device returns a TX completion with an error
code in the descriptor, in which case the respective socket
buffer and other relevant data structures may not be freed
or updated properly.

v3: Correct length of Fixes tags, requested by Jakub Kicinski

v2: Provide more detailed comments explaining specifically what
    reads are being ordered, suggested by Michael Ellerman
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -2404,6 +2404,12 @@ restart_poll:
 
 		if (!pending_scrq(adapter, adapter->rx_scrq[scrq_num]))
 			break;
+		/* The queue entry at the current index is peeked at above
+		 * to determine that there is a valid descriptor awaiting
+		 * processing. We want to be sure that the current slot
+		 * holds a valid descriptor before reading its contents.
+		 */
+		dma_rmb();
 		next = ibmvnic_next_scrq(adapter, adapter->rx_scrq[scrq_num]);
 		rx_buff =
 		    (struct ibmvnic_rx_buff *)be64_to_cpu(next->
@@ -3113,13 +3119,18 @@ restart_loop:
 		unsigned int pool = scrq->pool_index;
 		int num_entries = 0;
 
+		/* The queue entry at the current index is peeked at above
+		 * to determine that there is a valid descriptor awaiting
+		 * processing. We want to be sure that the current slot
+		 * holds a valid descriptor before reading its contents.
+		 */
+		dma_rmb();
+
 		next = ibmvnic_next_scrq(adapter, scrq);
 		for (i = 0; i < next->tx_comp.num_comps; i++) {
-			if (next->tx_comp.rcs[i]) {
+			if (next->tx_comp.rcs[i])
 				dev_err(dev, "tx error %x\n",
 					next->tx_comp.rcs[i]);
-				continue;
-			}
 			index = be32_to_cpu(next->tx_comp.correlators[i]);
 			if (index & IBMVNIC_TSO_POOL_MASK) {
 				tx_pool = &adapter->tso_pool[pool];
@@ -3513,6 +3524,11 @@ static union sub_crq *ibmvnic_next_scrq(struct ibmvnic_adapter *adapter,
 	}
 	spin_unlock_irqrestore(&scrq->lock, flags);
 
+	/* Ensure that the entire buffer descriptor has been
+	 * loaded before reading its contents
+	 */
+	dma_rmb();
+
 	return entry;
 }