netdev - Re: [PATCH] igb: cope with large MAX_SKB

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Message-ID: <ZiearYVLLy22H2eG@nanopsycho>
Date: Tue, 23 Apr 2024 13:25:33 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Corinna Vinschen <vinschen@...hat.com>
Cc: netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH] igb: cope with large MAX_SKB_FRAGS.

Tue, Apr 23, 2024 at 12:24:46PM CEST, vinschen@...hat.com wrote:
>From: Paolo Abeni <pabeni@...hat.com>
>
>Sabrina reports that the igb driver does not cope well with large
>MAX_SKB_FRAG values: setting MAX_SKB_FRAG to 45 causes payload
>corruption on TX.
>
>The root cause of the issue is that the driver does not take into
>account properly the (possibly large) shared info size when selecting
>the ring layout, and will try to fit two packets inside the same 4K
>page even when the 1st fraglist will trump over the 2nd head.
>
>Address the issue forcing the driver to fit a single packet per page,
>leaving there enough room to store the (currently) largest possible
>skb_shared_info.
>
>Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAG")
>Reported-by: Jan Tluka <jtluka@...hat.com>
>Reported-by: Jirka Hladky <jhladky@...hat.com>
>Reported-by: Sabrina Dubroca <sd@...asysnail.net>
>Tested-by: Sabrina Dubroca <sd@...asysnail.net>
>Tested-by: Corinna Vinschen <vinschen@...hat.com>
>Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Reviewed-by: Jiri Pirko <jiri@...dia.com>

Next time, please indicate target tree (net) in [patch] brackets.


>---
> drivers/net/ethernet/intel/igb/igb_main.c | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
>index a3f100769e39..22fb2c322bca 100644
>--- a/drivers/net/ethernet/intel/igb/igb_main.c
>+++ b/drivers/net/ethernet/intel/igb/igb_main.c
>@@ -4833,6 +4833,7 @@ static void igb_set_rx_buffer_len(struct igb_adapter *adapter,
> 
> #if (PAGE_SIZE < 8192)
> 	if (adapter->max_frame_size > IGB_MAX_FRAME_BUILD_SKB ||
>+	    SKB_HEAD_ALIGN(adapter->max_frame_size) > (PAGE_SIZE / 2) ||
> 	    rd32(E1000_RCTL) & E1000_RCTL_SBP)
> 		set_ring_uses_large_buffer(rx_ring);
> #endif
>-- 
>2.44.0
>
>