netdev - Re: [PATCH net] net: cpsw: avoid alignment faults by taking NET_IP

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Message-ID: <CAMj1kXFCWZ7sx-5_bRNv32OxLBsTSVGdqqzYSJXQtFAipQWmig@mail.gmail.com>
Date:   Tue, 18 Jan 2022 22:32:27 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "open list:BPF JIT for MIPS (32-BIT AND 64-BIT)" 
        <netdev@...r.kernel.org>, linux-omap <linux-omap@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "David S. Miller" <davem@...emloft.net>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>
Subject: Re: [PATCH net] net: cpsw: avoid alignment faults by taking
 NET_IP_ALIGN into account

On Tue, 18 Jan 2022 at 22:03, Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 18 Jan 2022 11:22:04 +0100 Ard Biesheuvel wrote:
> > Both versions of the CPSW driver declare a CPSW_HEADROOM_NA macro that
> > takes NET_IP_ALIGN into account, but fail to use it appropriately when
> > storing incoming packets in memory. This results in the IPv4 source and
> > destination addresses to appear misaligned in memory, which causes
> > aligment faults that need to be fixed up in software.
> >
> > So let's switch from CPSW_HEADROOM to CPSW_HEADROOM_NA where needed.
> > This gets rid of any alignment faults on the RX path on a Beaglebone
> > White.
> >
> > Cc: Grygorii Strashko <grygorii.strashko@...com>
> > Cc: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> > Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
>
> Fixes: 9ed4050c0d75 ("net: ethernet: ti: cpsw: add XDP support")
>

I suspect so, as that patch removes a call to
__netdev_alloc_skb_ip_align(), and replaces it with
page_pool_dev_alloc_pages() et al