[ 26/72] sfc: Properly sync RX DMA buffer when it is not the last in the page

Greg Kroah-Hartman
2013-03-26T23:20:08Z

From: Ben Hutchings <bhutchings@solarflare.com>

[ Upstream commit 3a68f19d7afb80f548d016effbc6ed52643a8085 ]

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>
[bwh: Backported to 3.4: adjust context]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/sfc/rx.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

--- a/drivers/net/ethernet/sfc/rx.c
+++ b/drivers/net/ethernet/sfc/rx.c
@@ -245,7 +245,8 @@ static int efx_init_rx_buffers_page(stru
}

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;
@@ -256,6 +257,10 @@ static void efx_unmap_rx_buffer(struct e
state->dma_addr,
efx_rx_buf_size(efx),
PCI_DMA_FROMDEVICE);
+ } 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) {
pci_unmap_single(efx->pci_dev, rx_buf->dma_addr,
@@ -278,7 +283,7 @@ static void efx_free_rx_buffer(struct ef
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);
}

@@ -544,10 +549,10 @@ void efx_rx_packet(struct efx_rx_queue *
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.