Message ID | 20190806092919.13211-1-firo.yang@suse.com |
---|---|
State | Awaiting Upstream |
Delegated to: | David Miller |
Headers | show |
Series | [1/1] ixgbe: sync the first fragment unconditionally | expand |
From: Firo Yang <firo.yang@suse.com> Date: Tue, 6 Aug 2019 09:29:51 +0000 > 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@suse.com> I don't understand, an unmap operation implies a sync operation.
On Tue, Aug 6, 2019 at 11:36 AM David Miller <davem@davemloft.net> wrote: > > From: Firo Yang <firo.yang@suse.com> > Date: Tue, 6 Aug 2019 09:29:51 +0000 > > > 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@suse.com> > > I don't understand, an unmap operation implies a sync operation. Actually it doesn't because ixgbe is mapping and unmapping with DMA_ATTR_SKIP_CPU_SYNC. The patch description isn't very good. The issue is that the sync in this case is being skipped in ixgbe_get_rx_buffer for a frame where the buffer spans more then a single page. As such we need to do both the sync and the unmap call on the last frame when we encounter the End Of Packet.
On Tue, Aug 6, 2019 at 2:38 AM Firo Yang <firo.yang@suse.com> wrote: > > 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@suse.com> From what I can tell the code below is fine. However the patch description isn't very clear about the issue. Specifically since we are mapping the frame with DMA_ATTR_SKIP_CPU_SYNC we have to unmap with that as well. As a result a sync is not performed on an unmap and must be done manually as we skipped it for the first frag. As such we need to always sync before possibly performing a page unmap operation. Also you can probably add the following to your patch description" Fixes: f3213d932173 ("ixgbe: Update driver to make use of DMA attributes in Rx path") Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.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 >
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); + } } /**
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@suse.com> --- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)