netdev - Re: [PATCH net] ixgbe: fix double clean of tx descriptors with xdp

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Date:   Wed, 21 Aug 2019 12:09:06 +0200
From:   "Eelco Chaudron" <echaudro@...hat.com>
To:     "Ilya Maximets" <i.maximets@...sung.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        "Björn Töpel" <bjorn.topel@...el.com>,
        "Magnus Karlsson" <magnus.karlsson@...el.com>,
        "Jakub Kicinski" <jakub.kicinski@...ronome.com>,
        "Alexei Starovoitov" <ast@...nel.org>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        "Jeff Kirsher" <jeffrey.t.kirsher@...el.com>,
        intel-wired-lan@...ts.osuosl.org, "William Tu" <u9012063@...il.com>
Subject: Re: [PATCH net] ixgbe: fix double clean of tx descriptors with xdp



On 20 Aug 2019, at 17:16, Ilya Maximets wrote:

> Tx code doesn't clear the descriptor status after cleaning.
> So, if the budget is larger than number of used elems in a ring, some
> descriptors will be accounted twice and xsk_umem_complete_tx will move
> prod_tail far beyond the prod_head breaking the comletion queue ring.
>
> Fix that by limiting the number of descriptors to clean by the number
> of used descriptors in the tx ring.
>
> Fixes: 8221c5eba8c1 ("ixgbe: add AF_XDP zero-copy Tx support")
> Signed-off-by: Ilya Maximets <i.maximets@...sung.com>
> ---
>
> Not tested yet because of lack of available hardware.
> So, testing is very welcome.
>
Hi Ilya, this patch fixes the issue I reported earlier on the Open 
vSwitch mailing list regarding complete queue overrun.

Tested-by: Eelco Chaudron <echaudro@...hat.com>

<SNIP>