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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Netanel Belgazal <netanel@amazon.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 119/168] net: ena: fix driver when PAGE_SIZE == 64kB
Date:   Mon,  8 Oct 2018 20:31:39 +0200
Message-Id: <20181008175624.571749146@linuxfoundation.org>
In-Reply-To: <20181008175620.043587728@linuxfoundation.org>
References: <20181008175620.043587728@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Netanel Belgazal <netanel@amazon.com>

[ Upstream commit ef5b0771d247379c90c8bf1332ff32f7f74bff7f ]

The buffer length field in the ena rx descriptor is 16 bit, and the
current driver passes a full page in each ena rx descriptor.
When PAGE_SIZE equals 64kB or more, the buffer length field becomes
zero.
To solve this issue, limit the ena Rx descriptor to use 16kB even
when allocating 64kB kernel pages. This change would not impact ena
device functionality, as 16kB is still larger than maximum MTU.

Signed-off-by: Netanel Belgazal <netanel@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c |   10 +++++-----
 drivers/net/ethernet/amazon/ena/ena_netdev.h |   11 +++++++++++
 2 files changed, 16 insertions(+), 5 deletions(-)

--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -461,7 +461,7 @@ static inline int ena_alloc_rx_page(stru
 		return -ENOMEM;
 	}
 
-	dma = dma_map_page(rx_ring->dev, page, 0, PAGE_SIZE,
+	dma = dma_map_page(rx_ring->dev, page, 0, ENA_PAGE_SIZE,
 			   DMA_FROM_DEVICE);
 	if (unlikely(dma_mapping_error(rx_ring->dev, dma))) {
 		u64_stats_update_begin(&rx_ring->syncp);
@@ -478,7 +478,7 @@ static inline int ena_alloc_rx_page(stru
 	rx_info->page_offset = 0;
 	ena_buf = &rx_info->ena_buf;
 	ena_buf->paddr = dma;
-	ena_buf->len = PAGE_SIZE;
+	ena_buf->len = ENA_PAGE_SIZE;
 
 	return 0;
 }
@@ -495,7 +495,7 @@ static void ena_free_rx_page(struct ena_
 		return;
 	}
 
-	dma_unmap_page(rx_ring->dev, ena_buf->paddr, PAGE_SIZE,
+	dma_unmap_page(rx_ring->dev, ena_buf->paddr, ENA_PAGE_SIZE,
 		       DMA_FROM_DEVICE);
 
 	__free_page(page);
@@ -916,10 +916,10 @@ static struct sk_buff *ena_rx_skb(struct
 	do {
 		dma_unmap_page(rx_ring->dev,
 			       dma_unmap_addr(&rx_info->ena_buf, paddr),
-			       PAGE_SIZE, DMA_FROM_DEVICE);
+			       ENA_PAGE_SIZE, DMA_FROM_DEVICE);
 
 		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, rx_info->page,
-				rx_info->page_offset, len, PAGE_SIZE);
+				rx_info->page_offset, len, ENA_PAGE_SIZE);
 
 		netif_dbg(rx_ring->adapter, rx_status, rx_ring->netdev,
 			  "rx skb updated. len %d. data_len %d\n",
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.h
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.h
@@ -355,4 +355,15 @@ void ena_dump_stats_to_buf(struct ena_ad
 
 int ena_get_sset_count(struct net_device *netdev, int sset);
 
+/* The ENA buffer length fields is 16 bit long. So when PAGE_SIZE == 64kB the
+ * driver passas 0.
+ * Since the max packet size the ENA handles is ~9kB limit the buffer length to
+ * 16kB.
+ */
+#if PAGE_SIZE > SZ_16K
+#define ENA_PAGE_SIZE SZ_16K
+#else
+#define ENA_PAGE_SIZE PAGE_SIZE
+#endif
+
 #endif /* !(ENA_H) */