redonkable/alistair23-linux
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sfc: Properly sync RX DMA buffer when it is not the last in the page

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We may currently allocate two RX DMA buffers to a page, and only unmap
the page when the second is completed.  We do not sync the first RX
buffer to be completed; this can result in packet loss or corruption
if the last RX buffer completed in a NAPI poll is the first in a page
and is not DMA-coherent.  (In the middle of a NAPI poll, we will
handle the following RX completion and unmap the page *before* looking
at the content of the first buffer.)

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
This commit is contained in:
Ben Hutchings 2012-12-20 18:48:20 +00:00
parent eb970ff07c
commit 3a68f19d7a
1 changed files with 10 additions and 5 deletions
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15
drivers/net/ethernet/sfc/rx.c
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@ -236,7 +236,8 @@ static int efx_init_rx_buffers_page(struct efx_rx_queue *rx_queue)
}
static void efx_unmap_rx_buffer(struct efx_nic *efx,
struct efx_rx_buffer *rx_buf)
struct efx_rx_buffer *rx_buf,
unsigned int used_len)
{
if ((rx_buf->flags & EFX_RX_BUF_PAGE) && rx_buf->u.page) {
struct efx_rx_page_state *state;
@ -247,6 +248,10 @@ static void efx_unmap_rx_buffer(struct efx_nic *efx,
state->dma_addr,
efx_rx_buf_size(efx),
DMA_FROM_DEVICE);
} else if (used_len) {
dma_sync_single_for_cpu(&efx->pci_dev->dev,
rx_buf->dma_addr, used_len,
DMA_FROM_DEVICE);
}
} else if (!(rx_buf->flags & EFX_RX_BUF_PAGE) && rx_buf->u.skb) {
dma_unmap_single(&efx->pci_dev->dev, rx_buf->dma_addr,
@ -269,7 +274,7 @@ static void efx_free_rx_buffer(struct efx_nic *efx,
static void efx_fini_rx_buffer(struct efx_rx_queue *rx_queue,
struct efx_rx_buffer *rx_buf)
{
efx_unmap_rx_buffer(rx_queue->efx, rx_buf);
efx_unmap_rx_buffer(rx_queue->efx, rx_buf, 0);
efx_free_rx_buffer(rx_queue->efx, rx_buf);
}
@ -535,10 +540,10 @@ void efx_rx_packet(struct efx_rx_queue *rx_queue, unsigned int index,
goto out;
}
/* Release card resources - assumes all RX buffers consumed in-order
* per RX queue
/* Release and/or sync DMA mapping - assumes all RX buffers
* consumed in-order per RX queue
*/
efx_unmap_rx_buffer(efx, rx_buf);
efx_unmap_rx_buffer(efx, rx_buf, len);
/* Prefetch nice and early so data will (hopefully) be in cache by
* the time we look at it.