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Tsirkin" To: Eli Cohen Subject: Re: VIRTIO_NET_F_MTU not negotiated Message-ID: <20220719093841-mutt-send-email-mst@kernel.org> References: MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Eugenio Perez Martin , "virtualization@lists.linux-foundation.org" X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Tue, Jul 19, 2022 at 01:25:42PM +0000, Eli Cohen wrote: > Hi, > > > > mlx5_vdpa is offering VIRTIO_NET_F_MTU. However the driver (is it qemu > responsibility?) does not accept and it ends up not negotiated. qemu is responsible for passing features to driver. > > > I don't see how can the driver refuse to negotiate this. What if the hardware > has a limitation with respect to mtu? Then it can fail FEATURES_OK > > > I noticed this when I created the device with mtu of 1000. I expected the > netdev at the vm to have mtu of 1000 and any attempt to go beyond should fail > but that's not the case. > > > > Comments? Any chance mtu is too small? if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) { int mtu = virtio_cread16(vdev, offsetof(struct virtio_net_config, mtu)); if (mtu < MIN_MTU) __virtio_clear_bit(vdev, VIRTIO_NET_F_MTU); } any chance it's on power or another BE system? -- MST _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization