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Message-ID: <11d1bf49-c417-b3cd-38e3-0f7d14dd8b12@intel.com>
Date:   Thu, 13 Apr 2023 09:54:59 -0700
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Subject: Re: [PATCH net 1/1] igc: read before write to SRRCTL register
Content-Language: en-US
To:     Song Yoong Siang <yoong.siang.song@intel.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Tony Nguyen <anthony.l.nguyen@intel.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "Alexei Starovoitov" <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        "Jesper Dangaard Brouer" <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Vedang Patel <vedang.patel@intel.com>,
        Jithu Joseph <jithu.joseph@intel.com>,
        Andre Guedes <andre.guedes@intel.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Stanislav Fomichev <sdf@google.com>
CC:     <intel-wired-lan@lists.osuosl.org>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>,
        <xdp-hints@xdp-project.net>, <stable@vger.kernel.org>
References: <20230413151222.1864307-1-yoong.siang.song@intel.com>
From:   Jacob Keller <jacob.e.keller@intel.com>
In-Reply-To: <20230413151222.1864307-1-yoong.siang.song@intel.com>
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On 4/13/2023 8:12 AM, Song Yoong Siang wrote:
> igc_configure_rx_ring() function will be called as part of XDP program
> setup. If Rx hardware timestamp is enabled prio to XDP program setup,
> this timestamp enablement will be overwritten when buffer size is
> written into SRRCTL register.
> 
> Thus, this commit read the register value before write to SRRCTL
> register. This commit is tested by using xdp_hw_metadata bpf selftest
> tool. The tool enables Rx hardware timestamp and then attach XDP program
> to igc driver. It will display hardware timestamp of UDP packet with
> port number 9092. Below are detail of test steps and results.
> 
> Command on DUT:
>   sudo ./xdp_hw_metadata <interface name>
> 
> Command on Link Partner:
>   echo -n skb | nc -u -q1 <destination IPv4 addr> 9092
> 
> Result before this patch:
>   skb hwtstamp is not found!
> 
> Result after this patch:
>   found skb hwtstamp = 1677762212.590696226
> 
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
> Cc: <stable@vger.kernel.org> # 5.14+
> Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>