netdev - [PATCH net] net: ethernet: mvneta: fix MVNETA_SKB

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Date:   Fri,  5 Jun 2020 15:53:24 +0300
From:   Alexander Lobakin <bloodyreaper@...dex.ru>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Sven Auhagen <sven.auhagen@...eatech.de>,
        Alexander Lobakin <bloodyreaper@...dex.ru>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH net] net: ethernet: mvneta: fix MVNETA_SKB_HEADROOM alignment

Commit ca23cb0bc50f ("mvneta: MVNETA_SKB_HEADROOM set last 3 bits to zero")
added headroom alignment check against 8.
Hovewer (if we imagine that NET_SKB_PAD or XDP_PACKET_HEADROOM is not
aligned to cacheline size), it actually aligns headroom down, while
skb/xdp_buff headroom should be *at least* equal to one of the values
(depending on XDP prog presence).
So, fix the check to align the value up. This satisfies both
hardware/driver and network stack requirements.

Fixes: ca23cb0bc50f ("mvneta: MVNETA_SKB_HEADROOM set last 3 bits to zero")
Signed-off-by: Alexander Lobakin <bloodyreaper@...dex.ru>
---
 drivers/net/ethernet/marvell/mvneta.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 011cd26953d9..4cc9abd61c43 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -325,7 +325,7 @@
 	      cache_line_size())
 
 /* Driver assumes that the last 3 bits are 0 */
-#define MVNETA_SKB_HEADROOM	(max(XDP_PACKET_HEADROOM, NET_SKB_PAD) & ~0x7)
+#define MVNETA_SKB_HEADROOM	ALIGN(max(NET_SKB_PAD, XDP_PACKET_HEADROOM), 8)
 #define MVNETA_SKB_PAD	(SKB_DATA_ALIGN(sizeof(struct skb_shared_info) + \
 			 MVNETA_SKB_HEADROOM))
 #define MVNETA_SKB_SIZE(len)	(SKB_DATA_ALIGN(len) + MVNETA_SKB_PAD)
-- 
2.27.0