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

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Date: Thu, 30 May 2024 18:29:51 +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 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).

Thanks