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

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Date:   Mon, 17 Apr 2023 06:43:39 +0000
From:   Alvaro Karsz <alvaro.karsz@...id-run.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
CC:     "jasowang@...hat.com" <jasowang@...hat.com>,
        "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

> > +static int virtnet_validate_vqs(struct virtnet_info *vi)
> > +{
> > +     u32 i, min_size = roundup_pow_of_two(MAX_SKB_FRAGS + 2);
> 
> why power of two?

The ring size is always a power of 2, so checking against MAX_SKB_FRAGS + 2 or against roundup_pow_of_two will result in the same, and I think that printing the warning with the actual min value is more helpful.
I can check the condition against MAX_SKB_FRAGS + 2, and print the rounded value in case of an error.