netdev - [PATCH] be2net: Bugfix for packet drop with kernel param swiotlb=force

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Date:	Thu, 20 Feb 2014 09:56:23 +0800
From:	jiang.biao2@....com.cn
To:	netdev@...r.kernel.org
Cc:	sathya.perla@...lex.com, subbu.seetharaman@...lex.com,
	ajit.khaparde@...lex.com, wang.liang82@....com.cn,
	cai.qu@....com.cn, li.fengmao@....com.cn, long.chun@....com.cn,
	David Miller <davem@...emloft.net>
Subject: [PATCH] be2net: Bugfix for packet drop with kernel param swiotlb=force


From: Li Fengmao <li.fengmao@....com.cn>

There will be packet drop with kernel param "swiotlb = force" on
Emulex 10Gb NIC using be2net driver. The problem is caused by
receiving skb without calling pci_unmap_page() in get_rx_page_info().
rx_page_info->last_page_user is initialized to false in
be_post_rx_frags() when current frag are mapped in the first half of
the same page with another frag. But in that case with
"swiotlb = force" param, data can not be copied into the page of
rx_page_info without calling pci_unmap_page, so the data frag mapped
in the first half of the page will be dropped.

It can be solved by creating only a mapping relation between frag
and page, and deleting rx_page_info->last_page_user to ensure
calling pci_unmap_page when handling each receiving frag.

Steps to reproduce the bug:
1. Prepare a Emulex Corporation OneConnect 10Gb NIC.
2. Add the kernel param like "swiotlb = force" in /boot/grub/grub.conf .
3. Reboot the system. (e.g exec reboot command)
4. Activate the interface. (e.g ifconfig eth0 192.168.1.2 up)
5. There will be packet drop when ping 192.168.1.2 from another host.

Signed-off-by: Li Fengmao <li.fengmao@....com.cn>
Signed-off-by: Long Chun <long.chun@....com.cn>
Reviewed-by: Wang Liang <wang.liang82@....com.cn>
Reviewed-by: Cai Qu <cai.qu@....com.cn>
Reviewed-by: Jiang Biao <jiang.biao2@....com.cn>

--- old/drivers/net/ethernet/emulex/benet/be_main.c	2014-02-20 08:49:49.322503588 +0800
+++ new/drivers/net/ethernet/emulex/benet/be_main.c	2014-02-20 08:56:38.796503104 +0800
@@ -1018,12 +1018,9 @@ get_rx_page_info(struct be_adapter *adap
 	rx_page_info = &rxo->page_info_tbl[frag_idx];
 	BUG_ON(!rx_page_info->page);

-	if (rx_page_info->last_page_user) {
-		dma_unmap_page(&adapter->pdev->dev,
-		               dma_unmap_addr(rx_page_info, bus),
-		               adapter->big_page_size, DMA_FROM_DEVICE);
-		rx_page_info->last_page_user = false;
-	}
+	dma_unmap_page(&adapter->pdev->dev,
+	               dma_unmap_addr(rx_page_info, bus),
+	               rx_frag_size, DMA_FROM_DEVICE);

 	atomic_dec(&rxq->used);
 	return rx_page_info;
@@ -1344,20 +1341,15 @@ static void be_post_rx_frags(struct be_r

 	page_info = &rxo->page_info_tbl[rxq->head];
 	for (posted = 0; posted < MAX_RX_POST && !page_info->page; posted++) {
-		if (!pagep) {
-			pagep = be_alloc_pages(adapter->big_page_size, gfp);
-			if (unlikely(!pagep)) {
-				rx_stats(rxo)->rx_post_fail++;
-				break;
-			}
-			page_dmaaddr = dma_map_page(&adapter->pdev->dev, pagep,
-			                            0, adapter->big_page_size,
-			                            DMA_FROM_DEVICE);
-			page_info->page_offset = 0;
-		} else {
-			get_page(pagep);
-			page_info->page_offset = page_offset + rx_frag_size;
+		pagep = be_alloc_pages(rx_frag_size, gfp);
+		if (unlikely(!pagep)) {
+			rx_stats(rxo)->rx_post_fail++;
+			break;
 		}
+		page_dmaaddr = dma_map_page(&adapter->pdev->dev, pagep,
+		                            0, rx_frag_size,
+		                            DMA_FROM_DEVICE);
+		page_info->page_offset = 0;
 		page_offset = page_info->page_offset;
 		page_info->page = pagep;
 		dma_unmap_addr_set(page_info, bus, page_dmaaddr);
@@ -1367,12 +1359,7 @@ static void be_post_rx_frags(struct be_r
 		rxd->fragpa_lo = cpu_to_le32(frag_dmaaddr & 0xFFFFFFFF);
 		rxd->fragpa_hi = cpu_to_le32(upper_32_bits(frag_dmaaddr));

-		/* Any space left in the current big page for another frag? */
-		if ((page_offset + rx_frag_size + rx_frag_size) >
-					adapter->big_page_size) {
-			pagep = NULL;
-			page_info->last_page_user = true;
-		}
+		pagep = NULL;

 		prev_page_info = page_info;
 		queue_head_inc(rxq);

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