[PATCH v2 1/1] ixgbe: sync the first fragment unconditionally

[Firo Yang]

In Xen environment, if Xen-swiotlb is enabled, ixgbe driver
could possibly allocate a page, DMA memory buffer, for the first
fragment which is not suitable for Xen-swiotlb to do DMA operations.
Xen-swiotlb have to internally allocate another page for doing DMA
operations. It requires syncing between those two pages. However,
since commit f3213d932173 ("ixgbe: Update driver to make use of DMA
attributes in Rx path"), the unmap operation is performed with
DMA_ATTR_SKIP_CPU_SYNC. As a result, the sync is not performed.

To fix this problem, always sync before possibly performing a page
unmap operation.

Fixes: f3213d932173 ("ixgbe: Update driver to make use of DMA
attributes in Rx path")
Reviewed-by: Alexander Duyck <alexander.h.du...@linux.intel.com>
Signed-off-by: Firo Yang <firo.y...@suse.com>
---

Changes from v1:
 * Imporved the patch description.
 * Added Reviewed-by: and Fixes: as suggested by Alexander Duyck

 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c 
b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index cbaf712d6529..200de9838096 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -1825,13 +1825,7 @@ static void ixgbe_pull_tail(struct ixgbe_ring *rx_ring,
 static void ixgbe_dma_sync_frag(struct ixgbe_ring *rx_ring,
                                struct sk_buff *skb)
 {
-       /* if the page was released unmap it, else just sync our portion */
-       if (unlikely(IXGBE_CB(skb)->page_released)) {
-               dma_unmap_page_attrs(rx_ring->dev, IXGBE_CB(skb)->dma,
-                                    ixgbe_rx_pg_size(rx_ring),
-                                    DMA_FROM_DEVICE,
-                                    IXGBE_RX_DMA_ATTR);
-       } else if (ring_uses_build_skb(rx_ring)) {
+       if (ring_uses_build_skb(rx_ring)) {
                unsigned long offset = (unsigned long)(skb->data) & ~PAGE_MASK;
 
                dma_sync_single_range_for_cpu(rx_ring->dev,
@@ -1848,6 +1842,14 @@ static void ixgbe_dma_sync_frag(struct ixgbe_ring 
*rx_ring,
                                              skb_frag_size(frag),
                                              DMA_FROM_DEVICE);
        }
+
+       /* If the page was released, just unmap it. */
+       if (unlikely(IXGBE_CB(skb)->page_released)) {
+               dma_unmap_page_attrs(rx_ring->dev, IXGBE_CB(skb)->dma,
+                                    ixgbe_rx_pg_size(rx_ring),
+                                    DMA_FROM_DEVICE,
+                                    IXGBE_RX_DMA_ATTR);
+       }
 }
 
 /**
-- 
2.16.4