linux-kernel - Re: [PATCH net-next V2] virtio-net: synchronize operstate with admin state on up/down

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Date: Thu, 30 May 2024 20:12:15 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: xuanzhuo@...ux.alibaba.com, eperezma@...hat.com, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>, 
	Gia-Khanh Nguyen <gia-khanh.nguyen@...cle.com>
Subject: Re: [PATCH net-next V2] virtio-net: synchronize operstate with admin
 state on up/down

On Thu, May 30, 2024 at 6:29 PM Jason Wang <jasowang@...hat.com> wrote:
>
> On Thu, May 30, 2024 at 2:10 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > On Thu, May 30, 2024 at 11:20:55AM +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
> > >
> > > Cc: Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>
> > > Cc: Gia-Khanh Nguyen <gia-khanh.nguyen@...cle.com>
> > > Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > > Acked-by: Michael S. Tsirkin <mst@...hat.com>
> > > Signed-off-by: Jason Wang <jasowang@...hat.com>
> > > ---
> > > Changes since V1:
> > > - rebase
> > > - add ack/review tags
> >
> >
> >
> >
> >
> > > ---
> > >  drivers/net/virtio_net.c | 94 +++++++++++++++++++++++++++-------------
> > >  1 file changed, 63 insertions(+), 31 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 4a802c0ea2cb..69e4ae353c51 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -433,6 +433,12 @@ struct virtnet_info {
> > >       /* The lock to synchronize the access to refill_enabled */
> > >       spinlock_t refill_lock;
> > >
> > > +     /* Is config change enabled? */
> > > +     bool config_change_enabled;
> > > +
> > > +     /* The lock to synchronize the access to config_change_enabled */
> > > +     spinlock_t config_change_lock;
> > > +
> > >       /* Work struct for config space updates */
> > >       struct work_struct config_work;
> > >
> >
> >
> > But we already have dev->config_lock and dev->config_enabled.
> >
> > And it actually works better - instead of discarding config
> > change events it defers them until enabled.
> >
>
> Yes but then both virtio-net driver and virtio core can ask to enable
> and disable and then we need some kind of synchronization which is
> non-trivial.
>
> And device enabling on the core is different from bringing the device
> up in the networking subsystem. Here we just delay to deal with the
> config change interrupt on ndo_open(). (E.g try to ack announce is
> meaningless when the device is down).

Or maybe you meant to make config_enabled a nest counter?

Thanks

>
> Thanks