netdev - Re: [PATCH 1/1] virtio/vsock: Make vsock virtio packet buff size configurable

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Date:   Mon, 12 Dec 2022 14:10:08 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Carlos Llamas <cmllamas@...gle.com>
Cc:     Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org,
        Ram Muthiah <rammuthiah@...gle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        netdev@...r.kernel.org, jiang.wang@...edance.com
Subject: Re: [PATCH 1/1] virtio/vsock: Make vsock virtio packet buff size
 configurable

On Fri, Dec 09, 2022 at 07:48:02PM +0000, Carlos Llamas wrote:
>On Thu, Jul 22, 2021 at 02:55:19PM +0200, Stefano Garzarella wrote:
>> >
>> > +uint virtio_transport_max_vsock_pkt_buf_size = 1024 * 64;
>> > +module_param(virtio_transport_max_vsock_pkt_buf_size, uint, 0444);
>> > +EXPORT_SYMBOL_GPL(virtio_transport_max_vsock_pkt_buf_size);
>> > +
>
>I'm interested on this functionality, so I could take this on.

Great!
We are changing the packet handling using sk_buff [1], so I think it's 
better to rebase on that work that should be merged in net-next after 
the current merge window will close.

>
>>
>> Maybe better to add an entry under sysfs similar to what Jiang proposed
>> here:
>> https://lists.linuxfoundation.org/pipermail/virtualization/2021-June/054769.html
>
>Having a look at Jiang's RFC patch it seems the proposed sysfs node
>hangs off from the main kernel object e.g. /sys/kernel. So I wonder if
>there is a more appropriate parent for this knob?

Agree, what about /sys/devices ?
I would take a closer look at what is recommend in this case.

>
>Also, I noticed that Ram's patch here is using read-only permissions for
>the module parameter and switching to sysfs would mean opening this knob
>up to be dynamically configured? I'd need to be careful here.
>

True, but even if it's changed while we're running, I don't think it's a 
big problem.

Maybe the problem here would be the allocation of RX buffers made during 
the probe. Could this be a good reason to use a module parameter?

Thanks,
Stefano

[1] 
https://lore.kernel.org/lkml/20221202173520.10428-1-bobby.eshleman@bytedance.com/