[Devel] [PATCH vz7] ixgbe: Fix packet corruption due to missing DMA sync

[Alexander Atanasov]

	When receiving a packet with multiple fragments, hardware may still
	touch the first fragment until the entire packet has been received. The
	driver therefore keeps the first fragment mapped for DMA until end of
	packet has been asserted, and delays its dma_sync call until then.

	The driver tries to fit multiple receive buffers on one page. When using
	3K receive buffers (e.g. using Jumbo frames and legacy-rx is turned
	off/build_skb is being used) on an architecture with 4K pages, the
	driver allocates an order 1 compound page and uses one page per receive
	buffer. To determine the correct offset for a delayed DMA sync of the
	first fragment of a multi-fragment packet, the driver then cannot just
	use PAGE_MASK on the DMA address but has to construct a mask based on
	the actual size of the backing page.

	Using PAGE_MASK in the 3K RX buffer/4K page architecture configuration
	will always sync the first page of a compound page. With the SWIOTLB
	enabled this can lead to corrupted packets (zeroed out first fragment,
	re-used garbage from another packet) and various consequences, such as
	slow/stalling data transfers and connection resets. For example, testing
	on a link with MTU exceeding 3058 bytes on a host with SWIOTLB enabled
	(e.g. "iommu=soft swiotlb=262144,force") TCP transfers quickly fizzle
	out without this patch.

	Cc: stable at vger.kernel.org
	Fixes: 0c5661ecc5dd7 ("ixgbe: fix crash in build_skb Rx code path")
	Signed-off-by: Markus Boehme <markubo at amazon.com>
	Tested-by: Tony Brelinski <tonyx.brelinski at intel.com>
	Signed-off-by: Tony Nguyen <anthony.l.nguyen at intel.com>
	Signed-off-by: David S. Miller <davem at davemloft.net>

(mainstream commit 09cfae9f13d51700b0fecf591dcd658fc5375428)
https://jira.sw.ru/browse/PSBM-142789
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index b39a1b477b24..725ddb36b846 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -1886,7 +1886,8 @@ static void ixgbe_dma_sync_frag(struct ixgbe_ring *rx_ring,
 				     DMA_FROM_DEVICE,
 				     &attrs);
 	} else if (ring_uses_build_skb(rx_ring)) {
-		unsigned long offset = (unsigned long)(skb->data) & ~PAGE_MASK;
+		unsigned long mask = (unsigned long)ixgbe_rx_pg_size(rx_ring) - 1;
+		unsigned long offset = (unsigned long)(skb->data) & mask;
 
 		dma_sync_single_range_for_cpu(rx_ring->dev,
 					      IXGBE_CB(skb)->dma,
-- 
2.31.1