igb: Revert support for build_skb in igb

This patch actually reverts:
igb: Support using build_skb in the case that jumbo frames are disabled

The reason for reverting this patch is that it can lead to data corruption.
The following flow was pointed out by Ben Hutchings:

1. skb is forwarded to another device
2. Packet headers are modified and it's put into a queue
3. Second packet is received into the other half of this page
4. Page cannot be reused, so is DMA-unmapped
5. The DMA mapping was non-coherent, so unmap copies or invalidates
cache

The headers added in step 2 get trashed in step 5.

Reported-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/igb/igb.h

@@ -284,18 +284,10 @@ struct igb_q_vector {
 enum e1000_ring_flags_t {
 	IGB_RING_FLAG_RX_SCTP_CSUM,
 	IGB_RING_FLAG_RX_LB_VLAN_BSWAP,
-	IGB_RING_FLAG_RX_BUILD_SKB_ENABLED,
 	IGB_RING_FLAG_TX_CTX_IDX,
 	IGB_RING_FLAG_TX_DETECT_HANG
 };
 
-#define ring_uses_build_skb(ring) \
-	test_bit(IGB_RING_FLAG_RX_BUILD_SKB_ENABLED, &(ring)->flags)
-#define set_ring_build_skb_enabled(ring) \
-	set_bit(IGB_RING_FLAG_RX_BUILD_SKB_ENABLED, &(ring)->flags)
-#define clear_ring_build_skb_enabled(ring) \
-	clear_bit(IGB_RING_FLAG_RX_BUILD_SKB_ENABLED, &(ring)->flags)
-
 #define IGB_TXD_DCMD (E1000_ADVTXD_DCMD_EOP | E1000_ADVTXD_DCMD_RS)
 
 #define IGB_RX_DESC(R, i)	    \

drivers/net/ethernet/intel/igb/igb_main.c

@@ -3350,20 +3350,6 @@ void igb_configure_rx_ring(struct igb_adapter *adapter,
 	wr32(E1000_RXDCTL(reg_idx), rxdctl);
 }
 
-static void igb_set_rx_buffer_len(struct igb_adapter *adapter,
-				  struct igb_ring *rx_ring)
-{
-#define IGB_MAX_BUILD_SKB_SIZE \
-	(SKB_WITH_OVERHEAD(IGB_RX_BUFSZ) - \
-	 (NET_SKB_PAD + NET_IP_ALIGN + IGB_TS_HDR_LEN))
-
-	/* set build_skb flag */
-	if (adapter->max_frame_size <= IGB_MAX_BUILD_SKB_SIZE)
-		set_ring_build_skb_enabled(rx_ring);
-	else
-		clear_ring_build_skb_enabled(rx_ring);
-}
-
 /**
  * igb_configure_rx - Configure receive Unit after Reset
  * @adapter: board private structure
@@ -3383,11 +3369,8 @@ static void igb_configure_rx(struct igb_adapter *adapter)
 
 	/* Setup the HW Rx Head and Tail Descriptor Pointers and
 	 * the Base and Length of the Rx Descriptor Ring */
-	for (i = 0; i < adapter->num_rx_queues; i++) {
-		struct igb_ring *rx_ring = adapter->rx_ring[i];
-		igb_set_rx_buffer_len(adapter, rx_ring);
-		igb_configure_rx_ring(adapter, rx_ring);
-	}
+	for (i = 0; i < adapter->num_rx_queues; i++)
+		igb_configure_rx_ring(adapter, adapter->rx_ring[i]);
 }
 
 /**
@@ -6203,78 +6186,6 @@ static bool igb_add_rx_frag(struct igb_ring *rx_ring,
 	return igb_can_reuse_rx_page(rx_buffer, page, truesize);
 }
 
-static struct sk_buff *igb_build_rx_buffer(struct igb_ring *rx_ring,
-					   union e1000_adv_rx_desc *rx_desc)
-{
-	struct igb_rx_buffer *rx_buffer;
-	struct sk_buff *skb;
-	struct page *page;
-	void *page_addr;
-	unsigned int size = le16_to_cpu(rx_desc->wb.upper.length);
-#if (PAGE_SIZE < 8192)
-	unsigned int truesize = IGB_RX_BUFSZ;
-#else
-	unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
-				SKB_DATA_ALIGN(NET_SKB_PAD +
-					       NET_IP_ALIGN +
-					       size);
-#endif
-
-	/* If we spanned a buffer we have a huge mess so test for it */
-	BUG_ON(unlikely(!igb_test_staterr(rx_desc, E1000_RXD_STAT_EOP)));
-
-	rx_buffer = &rx_ring->rx_buffer_info[rx_ring->next_to_clean];
-	page = rx_buffer->page;
-	prefetchw(page);
-
-	page_addr = page_address(page) + rx_buffer->page_offset;
-
-	/* prefetch first cache line of first page */
-	prefetch(page_addr + NET_SKB_PAD + NET_IP_ALIGN);
-#if L1_CACHE_BYTES < 128
-	prefetch(page_addr + L1_CACHE_BYTES + NET_SKB_PAD + NET_IP_ALIGN);
-#endif
-
-	/* build an skb to around the page buffer */
-	skb = build_skb(page_addr, truesize);
-	if (unlikely(!skb)) {
-		rx_ring->rx_stats.alloc_failed++;
-		return NULL;
-	}
-
-	/* we are reusing so sync this buffer for CPU use */
-	dma_sync_single_range_for_cpu(rx_ring->dev,
-				      rx_buffer->dma,
-				      rx_buffer->page_offset,
-				      IGB_RX_BUFSZ,
-				      DMA_FROM_DEVICE);
-
-	/* update pointers within the skb to store the data */
-	skb_reserve(skb, NET_IP_ALIGN + NET_SKB_PAD);
-	__skb_put(skb, size);
-
-	/* pull timestamp out of packet data */
-	if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) {
-		igb_ptp_rx_pktstamp(rx_ring->q_vector, skb->data, skb);
-		__skb_pull(skb, IGB_TS_HDR_LEN);
-	}
-
-	if (igb_can_reuse_rx_page(rx_buffer, page, truesize)) {
-		/* hand second half of page back to the ring */
-		igb_reuse_rx_page(rx_ring, rx_buffer);
-	} else {
-		/* we are not reusing the buffer so unmap it */
-		dma_unmap_page(rx_ring->dev, rx_buffer->dma,
-			       PAGE_SIZE, DMA_FROM_DEVICE);
-	}
-
-	/* clear contents of buffer_info */
-	rx_buffer->dma = 0;
-	rx_buffer->page = NULL;
-
-	return skb;
-}
-
 static struct sk_buff *igb_fetch_rx_buffer(struct igb_ring *rx_ring,
 					   union e1000_adv_rx_desc *rx_desc,
 					   struct sk_buff *skb)
@@ -6690,10 +6601,7 @@ static bool igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
 		rmb();
 
 		/* retrieve a buffer from the ring */
-		if (ring_uses_build_skb(rx_ring))
-			skb = igb_build_rx_buffer(rx_ring, rx_desc);
-		else
-			skb = igb_fetch_rx_buffer(rx_ring, rx_desc, skb);
+		skb = igb_fetch_rx_buffer(rx_ring, rx_desc, skb);
 
 		/* exit if we failed to retrieve a buffer */
 		if (!skb)
@@ -6780,14 +6688,6 @@ static bool igb_alloc_mapped_page(struct igb_ring *rx_ring,
 	return true;
 }
 
-static inline unsigned int igb_rx_offset(struct igb_ring *rx_ring)
-{
-	if (ring_uses_build_skb(rx_ring))
-		return NET_SKB_PAD + NET_IP_ALIGN;
-	else
-		return 0;
-}
-
 /**
  * igb_alloc_rx_buffers - Replace used receive buffers; packet split
  * @adapter: address of board private structure
@@ -6814,9 +6714,7 @@ void igb_alloc_rx_buffers(struct igb_ring *rx_ring, u16 cleaned_count)
 		 * Refresh the desc even if buffer_addrs didn't change
 		 * because each write-back erases this info.
 		 */
-		rx_desc->read.pkt_addr = cpu_to_le64(bi->dma +
-						     bi->page_offset +
-						     igb_rx_offset(rx_ring));
+		rx_desc->read.pkt_addr = cpu_to_le64(bi->dma + bi->page_offset);
 
 		rx_desc++;
 		bi++;