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Message-ID: <CACGkMEvDiQHfLaBRoaFtpYJHKTqicqbrpeZWzat43YveTa9Wyg@mail.gmail.com>
Date: Wed, 17 Jul 2024 09:19:02 +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 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
>
> >
> >
> > > Cc: Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>
> > > Cc: Gia-Khanh Nguyen <gia-khanh.nguyen@...cle.com>
> > > Signed-off-by: Jason Wang <jasowang@...hat.com>
> >
> > Yes but this just forces lots of re-reads of config on each
> > open/close for no good reason.
>
> Does it really harm? Technically the link status could be changed
> several times when the admin state is down as well.
>
> > Config interrupt is handled in core, you can read once
> > on probe and then handle config changes.
>
> Per RFC2863, the code tries to avoid dealing with any operstate change
> via config space read when the admin state is down.
>
> >
> >
> >
> >
> >
> > > ---
> > > drivers/net/virtio_net.c | 64 ++++++++++++++++++++++++----------------
> > > 1 file changed, 38 insertions(+), 26 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 0b4747e81464..e6626ba25b29 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -2476,6 +2476,25 @@ static void virtnet_cancel_dim(struct virtnet_info *vi, struct dim *dim)
> > > net_dim_work_cancel(dim);
> > > }
> > >
> > > +static void virtnet_update_settings(struct virtnet_info *vi)
> > > +{
> > > + u32 speed;
> > > + u8 duplex;
> > > +
> > > + if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_SPEED_DUPLEX))
> > > + return;
> > > +
> > > + virtio_cread_le(vi->vdev, struct virtio_net_config, speed, &speed);
> > > +
> > > + if (ethtool_validate_speed(speed))
> > > + vi->speed = speed;
> > > +
> > > + virtio_cread_le(vi->vdev, struct virtio_net_config, duplex, &duplex);
> > > +
> > > + if (ethtool_validate_duplex(duplex))
> > > + vi->duplex = duplex;
> > > +}
> > > +
> > > static int virtnet_open(struct net_device *dev)
> > > {
> > > struct virtnet_info *vi = netdev_priv(dev);
> > > @@ -2494,6 +2513,18 @@ static int virtnet_open(struct net_device *dev)
> > > goto err_enable_qp;
> > > }
> > >
> > > + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
> > > + virtio_config_driver_enable(vi->vdev);
> > > + /* Do not schedule the config change work as the
> > > + * config change notification might have been disabled
> > > + * by the virtio core. */
> >
> > I don't get why you need this.
> > If the notification was disabled it will just trigger later.
> > This is exactly why using core is a good idea.
>
> So we need a read here (this seems to be not rare for most modern
> hardware NICs) because we don't know if the link status is changed or
> not and it is not guaranteed by virtio_config_driver_enable() since it
> only works when there's a pending config change. Another thing is that
> the device is being freezed, so the virtio core may prevent the device
> from accessing the device.
>
> So using virtio_config_changed() will guaranteed that:
>
> 1) if the device is not being freezed, it will read the config space soon
> 2) if the device is being freezed, the read of the config space will
> be delayed to resume
>
> >
> >
> > > + virtio_config_changed(vi->vdev);
> > > + } else {
> > > + vi->status = VIRTIO_NET_S_LINK_UP;
> > > + virtnet_update_settings(vi);
> >
> >
> > And why do we need this here I don't get at all.
>
> See above, because doing this on a probe is racy and buggy: The
> opersate is up even if the adminstate is not, this is conflict with
> RFC2863:
>
> "
> If ifAdminStatus is down(2) then ifOperStatus
> should be down(2)
> "
>
> >
> > > + netif_carrier_on(dev);
> > > + }
> >
> >
> >
> > > +
> > > return 0;
> > >
> > > err_enable_qp:
> > > @@ -2936,12 +2967,19 @@ static int virtnet_close(struct net_device *dev)
> > > disable_delayed_refill(vi);
> > > /* Make sure refill_work doesn't re-enable napi! */
> > > cancel_delayed_work_sync(&vi->refill);
> > > + /* Make sure config notification doesn't schedule config work */
> > > + virtio_config_driver_disable(vi->vdev);
> > > + /* Make sure status updating is cancelled */
> > > + cancel_work_sync(&vi->config_work);
> > >
> > > for (i = 0; i < vi->max_queue_pairs; i++) {
> > > virtnet_disable_queue_pair(vi, i);
> > > virtnet_cancel_dim(vi, &vi->rq[i].dim);
> > > }
> > >
> > > + vi->status &= ~VIRTIO_NET_S_LINK_UP;
> > > + netif_carrier_off(dev);
> > > +
> > > return 0;
> > > }
> > >
> > > @@ -4640,25 +4678,6 @@ static void virtnet_init_settings(struct net_device *dev)
> > > vi->duplex = DUPLEX_UNKNOWN;
> > > }
> > >
> > > -static void virtnet_update_settings(struct virtnet_info *vi)
> > > -{
> > > - u32 speed;
> > > - u8 duplex;
> > > -
> > > - if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_SPEED_DUPLEX))
> > > - return;
> > > -
> > > - virtio_cread_le(vi->vdev, struct virtio_net_config, speed, &speed);
> > > -
> > > - if (ethtool_validate_speed(speed))
> > > - vi->speed = speed;
> > > -
> > > - virtio_cread_le(vi->vdev, struct virtio_net_config, duplex, &duplex);
> > > -
> > > - if (ethtool_validate_duplex(duplex))
> > > - vi->duplex = duplex;
> > > -}
> > > -
> > > static u32 virtnet_get_rxfh_key_size(struct net_device *dev)
> > > {
> > > return ((struct virtnet_info *)netdev_priv(dev))->rss_key_size;
> > > @@ -6000,13 +6019,6 @@ static int virtnet_probe(struct virtio_device *vdev)
> > > /* Assume link up if device can't report link status,
> > > otherwise get link status from config. */
> > > netif_carrier_off(dev);
> > > - if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
> > > - schedule_work(&vi->config_work);
> > > - } else {
> > > - vi->status = VIRTIO_NET_S_LINK_UP;
> > > - virtnet_update_settings(vi);
> > > - netif_carrier_on(dev);
> > > - }
> >
> >
> > Here it all made sense - we were reading config for the 1st time.
>
> See above.
>
> Thanks
>
> >
> >
> > > for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
> > > if (virtio_has_feature(vi->vdev, guest_offloads[i]))
> > > --
> > > 2.31.1
> >
> >
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