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

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Message-ID: <AM0PR04MB4723EB7A5E42A090F63EEC11D49C9@AM0PR04MB4723.eurprd04.prod.outlook.com>
Date:   Mon, 17 Apr 2023 07:07:59 +0000
From:   Alvaro Karsz <alvaro.karsz@...id-run.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.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>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH net] virtio-net: reject small vring sizes

> Why tx timeout without frags?

Please see my response to Michael.

> > * Guest GSO/big MTU (without VIRTIO_NET_F_MRG_RXBUF?), we can't chain page size buffers anymore.
> 
> 
> Or, we disable the GUEST_GSO, HOST_GSO......
> 
And disable VIRTIO_NET_F_MTU, quoting the spec:
"A driver SHOULD negotiate VIRTIO_NET_F_MTU if the device offers it."

We can find a way around using buffers bigger than a page size like Michael implied.