On Mon, Apr 17, 2023 at 06:38:43AM +0000, Alvaro Karsz wrote:> > Actually, I think that all you need to do is disable NETIF_F_SG, > > and things will work, no? > > I think that this is not so simple, if I understand correctly, by disabling NETIF_F_SG we will never receive a chained skbs to transmit, but we still have more functionality to address, for example: > * The TX timeouts.I don't get it. With a linear skb we can transmit it as long as there's space for 2 entries in the vq: header and data. What's the source of the timeouts?> * Guest GSO/big MTU (without VIRTIO_NET_F_MRG_RXBUF?), we can't chain page size buffers anymore.I think we can. mergeable_min_buf_len will just be large.> > Alvaro, can you try? > > It won't matter at the moment, we'll get TX timeout after the first tx packet, we need to address this part as well.
> > > Actually, I think that all you need to do is disable NETIF_F_SG, > > > and things will work, no? > > > > I think that this is not so simple, if I understand correctly, by disabling NETIF_F_SG we will never receive a chained skbs to transmit, but we still have more functionality to address, for example: > > * The TX timeouts. > > I don't get it. With a linear skb we can transmit it as long as there's > space for 2 entries in the vq: header and data. What's the source of the > timeouts? >I'm not saying that this is not possible, I meant that we need more changes to virtio-net. The source of the timeouts is from the current implementation of virtnet_poll_tx. if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) netif_tx_wake_queue(txq);> > * Guest GSO/big MTU (without VIRTIO_NET_F_MRG_RXBUF?), we can't chain page size buffers anymore. > > I think we can. mergeable_min_buf_len will just be large. >I meant that we can't just by clearing NETIF_F_SG, we'll need to change virtio-net a little bit more, for example, the virtnet_set_big_packets function.