sfc: Fix efx_rx_buf_offset() in the presence of swiotlb

We assume that the mapping between DMA and virtual addresses is done
on whole pages, so we can find the page offset of an RX buffer using
the lower bits of the DMA address.  However, swiotlb maps in units of
2K, breaking this assumption.

Add an explicit page_offset field to struct efx_rx_buffer.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/net/ethernet/sfc/rx.c b/drivers/net/ethernet/sfc/rx.c
index a5754916478e..879ff5849bbd 100644
--- a/drivers/net/ethernet/sfc/rx.c
+++ b/drivers/net/ethernet/sfc/rx.c
@@ -90,11 +90,7 @@ static unsigned int rx_refill_threshold;
 static inline unsigned int efx_rx_buf_offset(struct efx_nic *efx,
                                              struct efx_rx_buffer *buf)
 {
-        /* Offset is always within one page, so we don't need to consider
-         * the page order.
-         */
-        return ((unsigned int) buf->dma_addr & (PAGE_SIZE - 1)) +
-                efx->type->rx_buffer_hash_size;
+        return buf->page_offset + efx->type->rx_buffer_hash_size;
 }
 static inline unsigned int efx_rx_buf_size(struct efx_nic *efx)
 {
@@ -187,6 +183,7 @@ static int efx_init_rx_buffers_page(struct efx_rx_queue *rx_queue)
         struct efx_nic *efx = rx_queue->efx;
         struct efx_rx_buffer *rx_buf;
         struct page *page;
+        unsigned int page_offset;
         struct efx_rx_page_state *state;
         dma_addr_t dma_addr;
         unsigned index, count;
@@ -211,12 +208,14 @@ static int efx_init_rx_buffers_page(struct efx_rx_queue *rx_queue)
                 state->dma_addr = dma_addr;
 
                 dma_addr += sizeof(struct efx_rx_page_state);
+                page_offset = sizeof(struct efx_rx_page_state);
 
         split:
                 index = rx_queue->added_count & rx_queue->ptr_mask;
                 rx_buf = efx_rx_buffer(rx_queue, index);
                 rx_buf->dma_addr = dma_addr + EFX_PAGE_IP_ALIGN;
                 rx_buf->u.page = page;
+                rx_buf->page_offset = page_offset;
                 rx_buf->len = efx->rx_buffer_len - EFX_PAGE_IP_ALIGN;
                 rx_buf->flags = EFX_RX_BUF_PAGE;
                 ++rx_queue->added_count;
@@ -227,6 +226,7 @@ static int efx_init_rx_buffers_page(struct efx_rx_queue *rx_queue)
                         /* Use the second half of the page */
                         get_page(page);
                         dma_addr += (PAGE_SIZE >> 1);
+                        page_offset += (PAGE_SIZE >> 1);
                         ++count;
                         goto split;
                 }