vmxnet3: use DMA memory barriers where required

[ Upstream commit f3002c1374fb2367c9d8dbb28852791ef90d2bac ]

The gen bits must be read first from (resp. written last to) DMA memory.
The proper way to enforce this on Linux is to call dma_rmb() (resp.
dma_wmb()).

Signed-off-by: Regis Duchesne <hpreg@vmware.com>
Acked-by: Ronak Doshi <doshir@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
index 23cd3a3c4ab34536369af57d1b66ff5bc9e340a4..3628fd7e606fd001ac51b2b2762423ad23d7f725 100644 (file)
--- a/drivers/net/vmxnet3/vmxnet3_drv.c
+++ b/drivers/net/vmxnet3/vmxnet3_drv.c
@@ -369,6 +369,11 @@ vmxnet3_tq_tx_complete(struct vmxnet3_tx_queue *tq,
 
        gdesc = tq->comp_ring.base + tq->comp_ring.next2proc;
        while (VMXNET3_TCD_GET_GEN(&gdesc->tcd) == tq->comp_ring.gen) {
+               /* Prevent any &gdesc->tcd field from being (speculatively)
+                * read before (&gdesc->tcd)->gen is read.
+                */
+               dma_rmb();
+
                completed += vmxnet3_unmap_pkt(VMXNET3_TCD_GET_TXIDX(
                                               &gdesc->tcd), tq, adapter->pdev,
                                               adapter);
@@ -1099,6 +1104,11 @@ vmxnet3_tq_xmit(struct sk_buff *skb, struct vmxnet3_tx_queue *tq,
                gdesc->txd.tci = skb_vlan_tag_get(skb);
        }
 
+       /* Ensure that the write to (&gdesc->txd)->gen will be observed after
+        * all other writes to &gdesc->txd.
+        */
+       dma_wmb();
+
        /* finally flips the GEN bit of the SOP desc. */
        gdesc->dword[2] = cpu_to_le32(le32_to_cpu(gdesc->dword[2]) ^
                                                  VMXNET3_TXD_GEN);
@@ -1286,6 +1296,12 @@ vmxnet3_rq_rx_complete(struct vmxnet3_rx_queue *rq,
                         */
                        break;
                }
+
+               /* Prevent any rcd field from being (speculatively) read before
+                * rcd->gen is read.
+                */
+               dma_rmb();
+
                BUG_ON(rcd->rqID != rq->qid && rcd->rqID != rq->qid2 &&
                       rcd->rqID != rq->dataRingQid);
                idx = rcd->rxdIdx;
@@ -1515,6 +1531,12 @@ rcd_done:
                ring->next2comp = idx;
                num_to_alloc = vmxnet3_cmd_ring_desc_avail(ring);
                ring = rq->rx_ring + ring_idx;
+
+               /* Ensure that the writes to rxd->gen bits will be observed
+                * after all other writes to rxd objects.
+                */
+               dma_wmb();
+
                while (num_to_alloc) {
                        vmxnet3_getRxDesc(rxd, &ring->base[ring->next2fill].rxd,
                                          &rxCmdDesc);