netdev - Re: [virtio-dev] [RFC PATCH net-next v2 1/2] virtio_net: Introduce VIRTIO_NET_F

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Message-ID: <20180123020332-mutt-send-email-mst@kernel.org>
Date:   Tue, 23 Jan 2018 02:05:48 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        Jakub Kicinski <kubakici@...pl>,
        achiad shochat <achiad.mellanox@...il.com>,
        Achiad Shochat <achiad@...lanox.com>
Subject: Re: [virtio-dev] [RFC PATCH net-next v2 1/2] virtio_net: Introduce
 VIRTIO_NET_F_BACKUP feature bit

On Mon, Jan 22, 2018 at 03:27:40PM -0800, Samudrala, Sridhar wrote:
> > > You could probably
> > > even handle the Tx queue selection via a simple eBPF program and map
> > > since the input for whatever is used to select Tx should be pretty
> > > simple, destination MAC, source NUMA node, etc, and the data-set
> > > shouldn't be too large.
> > That sounds interesting. A separate device might make this kind of setup
> > a bit easier.  Sridhar, did you look into creating a separate device for
> > the virtual bond device at all?  It does not have to be in a separate
> > module, that kind of refactoring can come later, but once we commit to
> > using the same single device as virtio, we can't change that.
> 
> No. I haven't looked into creating a separate device. If we are going to
> create a new
> device, i guess it has to be of a new device type with its own driver.

Well not necessarily - just a separate netdev ops.
Kind of like e.g. vlans share a driver with the main driver.

> As we are using virtio_net to control and manage the VF data path, it is not
> clear to me
> what is the advantage of creating a new device rather than extending
> virtio_net to manage
> the VF datapath via transparent bond mechanism.
> 
> Thanks
> Sridhar

So that XDP redirect actions can differentiate between virtio, PT
device and the bond. Without it there's no way to redirect
to virtio specifically.

-- 
MST