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[80.230.79.166]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b45e5c233sm6464487f8f.33.2026.03.16.05.04.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2026 05:04:45 -0700 (PDT) Date: Mon, 16 Mar 2026 08:04:41 -0400 From: "Michael S. Tsirkin" To: Vishwanath Seshagiri Cc: Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Lunn , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Wei , Matteo Croce , Ilias Apalodimas , netdev@vger.kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH net-next v11] virtio_net: add page_pool support for buffer allocation Message-ID: <20260316080419-mutt-send-email-mst@kernel.org> References: <20260310183107.2822016-1-vishs@meta.com> <20260316054232-mutt-send-email-mst@kernel.org> <20260316064256-mutt-send-email-mst@kernel.org> <6d43dbbb-7d04-4442-8743-3963b61195cd@meta.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <6d43dbbb-7d04-4442-8743-3963b61195cd@meta.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: _nzQm_P7y2sRCThVRJo0tAdUpH9LK2AMJaNfXxyOuxM_1773662687 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Mar 16, 2026 at 05:27:57PM +0530, Vishwanath Seshagiri wrote: > On 3/16/26 4:13 PM, Michael S. Tsirkin wrote: > > On Mon, Mar 16, 2026 at 05:56:20AM -0400, Michael S. Tsirkin wrote: > > > On Tue, Mar 10, 2026 at 11:31:04AM -0700, Vishwanath Seshagiri wrote: > > > > @@ -5857,7 +5863,7 @@ static int virtnet_xsk_pool_enable(struct net_device *dev, > > > > /* In big_packets mode, xdp cannot work, so there is no need to > > > > * initialize xsk of rq. > > > > */ > > > > - if (vi->big_packets && !vi->mergeable_rx_bufs) > > > > + if (!vi->rq[qid].page_pool) > > > > return -ENOENT; > > > > if (qid >= vi->curr_queue_pairs) > > > > > > > > > > > > It seems that a qid that exceeds curr_queue_pairs would previously get > > > -EINVAL and now gets -ENOENT. > > > > Or maybe this if (qid >= vi->curr_queue_pairs) is dead code? > > I looked at it some more and I can't find a path where this > > triggers. > > > > > Maybe reorder the checks: > > > > > > if (qid >= vi->curr_queue_pairs) > > > return -EINVAL; > > > > > > /* In big_packets mode, xdp cannot work, so there is no need to > > > * initialize xsk of rq. > > > */ > > > if (!vi->rq[qid].page_pool) > > > return -ENOENT; > > > > > > > > > Alternatively I think we can completely drop this chunk: we already seem > > > to init page_pull at all times except for big packets mode, so the > > > current code is fine I think. > > Yes, I agree qid >= curr_queue_pairs appears to be dead code. > xsk_reg_pool_at_qid() in the XSK core already validates > queue_id < max(real_num_rx_queues, real_num_tx_queues) before > ndo_bpf is called, and real_num_rx_queues == curr_queue_pairs is an > invariant in virtio_net. Both paths hold rtnl_lock so no race is > possible. That said, I'll adopt your suggested reorder for v12 to ensure > vi->rq[qid] isn't accessed before a bounds check, even if the check > is currently redundant. I think we can just take this as-is, and do more cleanups on top. Acked-by: Michael S. Tsirkin > > > > > > > > > -- > > > MST > >