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

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Date:   Tue, 6 Aug 2019 09:29:51 +0000
From:   Firo Yang <firo.yang@...e.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "jeffrey.t.kirsher@...el.com" <jeffrey.t.kirsher@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Firo Yang <firo.yang@...e.com>
Subject: [PATCH 1/1] ixgbe: sync the first fragment unconditionally

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 will internally allocate another page for doing DMA
operations. It requires syncing between those two pages. Otherwise,
we may get an incomplete skb. To fix this problem, sync the first
fragment no matter the first fargment is makred as "page_released"
or not.

Signed-off-by: Firo Yang <firo.yang@...e.com>
---
 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