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From:   "Eelco Chaudron" <echaudro@redhat.com>
To:     "Ilya Maximets" <i.maximets@samsung.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
        "=?utf-8?b?QmrDtnJuIFTDtnBlbA==?=" <bjorn.topel@intel.com>,
        "Magnus Karlsson" <magnus.karlsson@intel.com>,
        "Jakub Kicinski" <jakub.kicinski@netronome.com>,
        "Alexei Starovoitov" <ast@kernel.org>,
        "Daniel Borkmann" <daniel@iogearbox.net>,
        "Jeff Kirsher" <jeffrey.t.kirsher@intel.com>,
        intel-wired-lan@lists.osuosl.org, "William Tu" <u9012063@gmail.com>
Subject: Re: [PATCH net] ixgbe: fix double clean of tx descriptors with xdp
Date:   Wed, 21 Aug 2019 12:09:06 +0200
Message-ID: <9EFD9B47-2CD0-4D7A-BA22-D87018894E91@redhat.com>
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 <20190820151611.10727-1-i.maximets@samsung.com>
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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@samsung.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@redhat.com>

<SNIP>