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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Netanel Belgazal <netanel@amazon.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.18 41/65] net: ena: fix driver when PAGE_SIZE ==
 64kB
Thread-Topic: [PATCH AUTOSEL 4.18 41/65] net: ena: fix driver when PAGE_SIZE
 == 64kB
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Date:   Mon, 1 Oct 2018 00:38:28 +0000
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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>
---
 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(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/eth=
ernet/amazon/ena/ena_netdev.c
index 26686a21234e..e6537d35408c 100644
--- 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(struct ena_ring *rx=
_ring,
 		return -ENOMEM;
 	}
=20
-	dma =3D dma_map_page(rx_ring->dev, page, 0, PAGE_SIZE,
+	dma =3D 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(struct ena_ring *rx=
_ring,
 	rx_info->page_offset =3D 0;
 	ena_buf =3D &rx_info->ena_buf;
 	ena_buf->paddr =3D dma;
-	ena_buf->len =3D PAGE_SIZE;
+	ena_buf->len =3D ENA_PAGE_SIZE;
=20
 	return 0;
 }
@@ -495,7 +495,7 @@ static void ena_free_rx_page(struct ena_ring *rx_ring,
 		return;
 	}
=20
-	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);
=20
 	__free_page(page);
@@ -916,10 +916,10 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx=
_ring,
 	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);
=20
 		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);
=20
 		netif_dbg(rx_ring->adapter, rx_status, rx_ring->netdev,
 			  "rx skb updated. len %d. data_len %d\n",
diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.h b/drivers/net/eth=
ernet/amazon/ena/ena_netdev.h
index f1972b5ab650..7c7ae56c52cf 100644
--- 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_adapter *adapter=
, u8 *buf);
=20
 int ena_get_sset_count(struct net_device *netdev, int sset);
=20
+/* The ENA buffer length fields is 16 bit long. So when PAGE_SIZE =3D=3D 6=
4kB the
+ * driver passas 0.
+ * Since the max packet size the ENA handles is ~9kB limit the buffer leng=
th to
+ * 16kB.
+ */
+#if PAGE_SIZE > SZ_16K
+#define ENA_PAGE_SIZE SZ_16K
+#else
+#define ENA_PAGE_SIZE PAGE_SIZE
+#endif
+
 #endif /* !(ENA_H) */
--=20
2.17.1