linux-kernel - Re: [PATCH net] virtio-net: reject small vring sizes

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Message-ID: <AM0PR04MB4723B8489F8F9AE547393697D49C9@AM0PR04MB4723.eurprd04.prod.outlook.com>
Date:   Mon, 17 Apr 2023 06:38:43 +0000
From:   Alvaro Karsz <alvaro.karsz@...id-run.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] virtio-net: reject small vring sizes

> 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.
* Guest GSO/big MTU (without VIRTIO_NET_F_MRG_RXBUF?), we can't chain page size buffers anymore.

> 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.