netdev - Re: [PATCH net-next 1/5] net: tso: double TSO_HEADER

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Message-ID: <20200617170229.04454d36@kicinski-fedora-PC1C0HJN>
Date:   Wed, 17 Jun 2020 17:02:29 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Antoine Tenart <antoine.tenart@...tlin.com>
Subject: Re: [PATCH net-next 1/5] net: tso: double TSO_HEADER_SIZE value

On Wed, 17 Jun 2020 11:48:15 -0700 Eric Dumazet wrote:
> Transport header size could be 60 bytes, and network header
> size can also be 60 bytes. Add the Ethernet header and we
> are above 128 bytes.
> 
> Since drivers using net/core/tso.c usually allocates
> one DMA coherent piece of memory per TX queue, this patch
> might cause issues if a driver was using too many slots.
> 
> For 1024 slots, we would need 256 KB of physically
> contiguous memory instead of 128 KB.
> 
> Alternative fix would be to add checks in the fast path,
> but this involves more work in all drivers using net/core/tso.c.
> 
> Fixes: f9cbe9a556af ("net: define the TSO header size in net/tso.h")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Antoine Tenart <antoine.tenart@...tlin.com>

Some warnings popping up in this series with W=1 C=1:

drivers/net/ethernet/marvell/octeontx2/af/common.h:65:26: warning: cast truncates bits from constant value (100 becomes 0)