linux-kernel - Re: [PATCH net-next v3 3/3] virtio-net: synchronize operstate with admin state on up/down

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Message-ID: <CACGkMEtntsAyddgrtxrbQe407dZkitac4ogC7cASF=iYgsum_A@mail.gmail.com>
Date: Wed, 17 Jul 2024 14:53:00 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: xuanzhuo@...ux.alibaba.com, eperezma@...hat.com, 
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	netdev@...r.kernel.org, Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>, 
	Gia-Khanh Nguyen <gia-khanh.nguyen@...cle.com>
Subject: Re: [PATCH net-next v3 3/3] virtio-net: synchronize operstate with
 admin state on up/down

On Wed, Jul 17, 2024 at 2:00 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Wed, Jul 17, 2024 at 09:19:02AM +0800, Jason Wang wrote:
> > On Wed, Jul 10, 2024 at 11:03 AM Jason Wang <jasowang@...hat.com> wrote:
> > >
> > > On Tue, Jul 9, 2024 at 9:28 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> > > >
> > > > On Tue, Jul 09, 2024 at 04:02:14PM +0800, Jason Wang wrote:
> > > > > This patch synchronize operstate with admin state per RFC2863.
> > > > >
> > > > > This is done by trying to toggle the carrier upon open/close and
> > > > > synchronize with the config change work. This allows propagate status
> > > > > correctly to stacked devices like:
> > > > >
> > > > > ip link add link enp0s3 macvlan0 type macvlan
> > > > > ip link set link enp0s3 down
> > > > > ip link show
> > > > >
> > > > > Before this patch:
> > > > >
> > > > > 3: enp0s3: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 1000
> > > > >     link/ether 00:00:05:00:00:09 brd ff:ff:ff:ff:ff:ff
> > > > > ......
> > > > > 5: macvlan0@...0s3: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
> > > > >     link/ether b2:a9:c5:04:da:53 brd ff:ff:ff:ff:ff:ff
> > > > >
> > > > > After this patch:
> > > > >
> > > > > 3: enp0s3: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 1000
> > > > >     link/ether 00:00:05:00:00:09 brd ff:ff:ff:ff:ff:ff
> > > > > ...
> > > > > 5: macvlan0@...0s3: <NO-CARRIER,BROADCAST,MULTICAST,UP,M-DOWN> mtu 1500 qdisc noqueue state LOWERLAYERDOWN mode DEFAULT group default qlen 1000
> > > > >     link/ether b2:a9:c5:04:da:53 brd ff:ff:ff:ff:ff:ff
> > > >
> > > > I think that the commit log is confusing. It seems to say that
> > > > the issue fixed is synchronizing state with hardware
> > > > config change.
> > > > But your example does not show any
> > > > hardware change. Isn't this example really just
> > > > a side effect of setting carrier off on close?
> > >
> > > The main goal for this patch is to make virtio-net follow RFC2863. The
> > > main thing that is missed is to synchronize the operstate with admin
> > > state, if we do this, we get several good results, one of the obvious
> > > one is to allow virtio-net to propagate status to the upper layer, for
> > > example if the admin state of the lower virtio-net is down it should
> > > be propagated to the macvlan on top, so I give the example of using a
> > > stacked device. I'm not we had others but the commit log is probably
> > > too small to say all of it.
> >
> > Michael, any more comments on this?
> >
> > Thans
>
>
> Still don't get it, sorry.
> > > > > This is done by trying to toggle the carrier upon open/close and
> > > > > synchronize with the config change work.
> What does this sentence mean? What is not synchronized with config
> change that needs to be?

I meant,

1) maclvan depends on the linkwatch to transfer operstate from the
lower device to itself.
2) ndo_open()/close() will not trigger the linkwatch so we need to do
it by ourselves in virtio-net to make sure macvlan get the correct
opersate
3) consider config change work can change the state so ndo_close()
needs to synchronize with it

Thanks