netdev - [PATCH net 2/3] bnxt_en: reserve space inside receive page for skb_shared

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Date:   Fri,  1 Apr 2022 20:21:11 -0400
From:   Michael Chan <michael.chan@...adcom.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, kuba@...nel.org, gospo@...adcom.com,
        bpf@...r.kernel.org
Subject: [PATCH net 2/3] bnxt_en: reserve space inside receive page for skb_shared_info

From: Andy Gospodarek <gospo@...adcom.com>

Insufficient space was being reserved in the page used for packet
reception, so the interface MTU could be set too large to still have
room for the contents of the packet when doing XDP redirect.  This
resulted in the following message when redirecting a packet between
3520 and 3822 bytes with an MTU of 3822:

[311815.561880] XDP_WARN: xdp_update_frame_from_buff(line:200): Driver BUG: missing reserved tailroom

Fixes: f18c2b77b2e4 ("bnxt_en: optimized XDP_REDIRECT support")
Reviewed-by: Somnath Kotur <somnath.kotur@...adcom.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@...adcom.com>
Signed-off-by: Andy Gospodarek <gospo@...adcom.com>
Signed-off-by: Michael Chan <michael.chan@...adcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index b4d3d051463b..98453a78cbd0 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -593,7 +593,8 @@ struct nqe_cn {
 #define BNXT_MAX_MTU		9500
 #define BNXT_MAX_PAGE_MODE_MTU	\
 	((unsigned int)PAGE_SIZE - VLAN_ETH_HLEN - NET_IP_ALIGN -	\
-	 XDP_PACKET_HEADROOM)
+	 XDP_PACKET_HEADROOM - \
+	 SKB_DATA_ALIGN((unsigned int)sizeof(struct skb_shared_info)))
 
 #define BNXT_MIN_PKT_SIZE	52
 
-- 
2.18.1


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