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([2001:ee0:4f0e:fb30:fe1:cf75:ee2d:d934]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23506cd8cf0sm120472525ad.155.2025.06.05.07.33.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Jun 2025 07:33:31 -0700 (PDT) Message-ID: Date: Thu, 5 Jun 2025 21:33:26 +0700 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] virtio-net: drop the multi-buffer XDP packet in zerocopy To: Paolo Abeni , netdev@vger.kernel.org Cc: "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, stable@vger.kernel.org References: <20250603150613.83802-1-minhquangbui99@gmail.com> Content-Language: en-US From: Bui Quang Minh In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/5/25 18:03, Paolo Abeni wrote: > On 6/3/25 5:06 PM, Bui Quang Minh wrote: >> In virtio-net, we have not yet supported multi-buffer XDP packet in >> zerocopy mode when there is a binding XDP program. However, in that >> case, when receiving multi-buffer XDP packet, we skip the XDP program >> and return XDP_PASS. As a result, the packet is passed to normal network >> stack which is an incorrect behavior. > Why? AFAICS the multi-buffer mode depends on features negotiation, which > is not controlled by the VM user. > > Let's suppose the user wants to attach an XDP program to do some per > packet stats accounting. That suddenly would cause drop packets > depending on conditions not controlled by the (guest) user. It looks > wrong to me. But currently, if a multi-buffer packet arrives, it will not go through XDP program so it doesn't increase the stats but still goes to network stack. So I think it's not a correct behavior. > > XDP_ABORTED looks like a better choice. > > /P > Thanks, Quang Minh.