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Message-ID: <20230414031947-mutt-send-email-mst@kernel.org>
Date: Fri, 14 Apr 2023 03:21:38 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, maxime.coquelin@...hat.com,
alvaro.karsz@...id-run.com, eperezma@...hat.com,
xuanzhuo@...ux.alibaba.com, david.marchand@...hat.com,
netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next V2 1/2] virtio-net: convert rx mode setting to
use workqueue
On Fri, Apr 14, 2023 at 01:04:15PM +0800, Jason Wang wrote:
> Forget to cc netdev, adding.
>
> On Fri, Apr 14, 2023 at 12:25 AM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > On Thu, Apr 13, 2023 at 02:40:26PM +0800, Jason Wang wrote:
> > > This patch convert rx mode setting to be done in a workqueue, this is
> > > a must for allow to sleep when waiting for the cvq command to
> > > response since current code is executed under addr spin lock.
> > >
> > > Signed-off-by: Jason Wang <jasowang@...hat.com>
> >
> > I don't like this frankly. This means that setting RX mode which would
> > previously be reliable, now becomes unreliable.
>
> It is "unreliable" by design:
>
> void (*ndo_set_rx_mode)(struct net_device *dev);
>
> > - first of all configuration is no longer immediate
>
> Is immediate a hard requirement? I can see a workqueue is used at least:
>
> mlx5e, ipoib, efx, ...
>
> > and there is no way for driver to find out when
> > it actually took effect
>
> But we know rx mode is best effort e.g it doesn't support vhost and we
> survive from this for years.
>
> > - second, if device fails command, this is also not
> > propagated to driver, again no way for driver to find out
> >
> > VDUSE needs to be fixed to do tricks to fix this
> > without breaking normal drivers.
>
> It's not specific to VDUSE. For example, when using virtio-net in the
> UP environment with any software cvq (like mlx5 via vDPA or cma
> transport).
>
> Thanks
Hmm. Can we differentiate between these use-cases?
> >
> >
> > > ---
> > > Changes since V1:
> > > - use RTNL to synchronize rx mode worker
> > > ---
> > > drivers/net/virtio_net.c | 55 +++++++++++++++++++++++++++++++++++++---
> > > 1 file changed, 52 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index e2560b6f7980..2e56bbf86894 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -265,6 +265,12 @@ struct virtnet_info {
> > > /* Work struct for config space updates */
> > > struct work_struct config_work;
> > >
> > > + /* Work struct for config rx mode */
> > > + struct work_struct rx_mode_work;
> > > +
> > > + /* Is rx mode work enabled? */
> > > + bool rx_mode_work_enabled;
> > > +
> > > /* Does the affinity hint is set for virtqueues? */
> > > bool affinity_hint_set;
> > >
> > > @@ -388,6 +394,20 @@ static void disable_delayed_refill(struct virtnet_info *vi)
> > > spin_unlock_bh(&vi->refill_lock);
> > > }
> > >
> > > +static void enable_rx_mode_work(struct virtnet_info *vi)
> > > +{
> > > + rtnl_lock();
> > > + vi->rx_mode_work_enabled = true;
> > > + rtnl_unlock();
> > > +}
> > > +
> > > +static void disable_rx_mode_work(struct virtnet_info *vi)
> > > +{
> > > + rtnl_lock();
> > > + vi->rx_mode_work_enabled = false;
> > > + rtnl_unlock();
> > > +}
> > > +
> > > static void virtqueue_napi_schedule(struct napi_struct *napi,
> > > struct virtqueue *vq)
> > > {
> > > @@ -2310,9 +2330,11 @@ static int virtnet_close(struct net_device *dev)
> > > return 0;
> > > }
> > >
> > > -static void virtnet_set_rx_mode(struct net_device *dev)
> > > +static void virtnet_rx_mode_work(struct work_struct *work)
> > > {
> > > - struct virtnet_info *vi = netdev_priv(dev);
> > > + struct virtnet_info *vi =
> > > + container_of(work, struct virtnet_info, rx_mode_work);
> > > + struct net_device *dev = vi->dev;
> > > struct scatterlist sg[2];
> > > struct virtio_net_ctrl_mac *mac_data;
> > > struct netdev_hw_addr *ha;
> > > @@ -2325,6 +2347,8 @@ static void virtnet_set_rx_mode(struct net_device *dev)
> > > if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
> > > return;
> > >
> > > + rtnl_lock();
> > > +
> > > vi->ctrl->promisc = ((dev->flags & IFF_PROMISC) != 0);
> > > vi->ctrl->allmulti = ((dev->flags & IFF_ALLMULTI) != 0);
> > >
> > > @@ -2342,14 +2366,19 @@ static void virtnet_set_rx_mode(struct net_device *dev)
> > > dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
> > > vi->ctrl->allmulti ? "en" : "dis");
> > >
> > > + netif_addr_lock_bh(dev);
> > > +
> > > uc_count = netdev_uc_count(dev);
> > > mc_count = netdev_mc_count(dev);
> > > /* MAC filter - use one buffer for both lists */
> > > buf = kzalloc(((uc_count + mc_count) * ETH_ALEN) +
> > > (2 * sizeof(mac_data->entries)), GFP_ATOMIC);
> > > mac_data = buf;
> > > - if (!buf)
> > > + if (!buf) {
> > > + netif_addr_unlock_bh(dev);
> > > + rtnl_unlock();
> > > return;
> > > + }
> > >
> > > sg_init_table(sg, 2);
> > >
> > > @@ -2370,6 +2399,8 @@ static void virtnet_set_rx_mode(struct net_device *dev)
> > > netdev_for_each_mc_addr(ha, dev)
> > > memcpy(&mac_data->macs[i++][0], ha->addr, ETH_ALEN);
> > >
> > > + netif_addr_unlock_bh(dev);
> > > +
> > > sg_set_buf(&sg[1], mac_data,
> > > sizeof(mac_data->entries) + (mc_count * ETH_ALEN));
> > >
> > > @@ -2377,9 +2408,19 @@ static void virtnet_set_rx_mode(struct net_device *dev)
> > > VIRTIO_NET_CTRL_MAC_TABLE_SET, sg))
> > > dev_warn(&dev->dev, "Failed to set MAC filter table.\n");
> > >
> > > + rtnl_unlock();
> > > +
> > > kfree(buf);
> > > }
> > >
> > > +static void virtnet_set_rx_mode(struct net_device *dev)
> > > +{
> > > + struct virtnet_info *vi = netdev_priv(dev);
> > > +
> > > + if (vi->rx_mode_work_enabled)
> > > + schedule_work(&vi->rx_mode_work);
> > > +}
> > > +
> > > static int virtnet_vlan_rx_add_vid(struct net_device *dev,
> > > __be16 proto, u16 vid)
> > > {
> > > @@ -3150,6 +3191,8 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
> > >
> > > /* Make sure no work handler is accessing the device */
> > > flush_work(&vi->config_work);
> > > + disable_rx_mode_work(vi);
> > > + flush_work(&vi->rx_mode_work);
> > >
> > > netif_tx_lock_bh(vi->dev);
> > > netif_device_detach(vi->dev);
> >
> > So now configuration is not propagated to device.
> > Won't device later wake up in wrong state?
> >
> >
> > > @@ -3172,6 +3215,7 @@ static int virtnet_restore_up(struct virtio_device *vdev)
> > > virtio_device_ready(vdev);
> > >
> > > enable_delayed_refill(vi);
> > > + enable_rx_mode_work(vi);
> > >
> > > if (netif_running(vi->dev)) {
> > > err = virtnet_open(vi->dev);
> > > @@ -3969,6 +4013,7 @@ static int virtnet_probe(struct virtio_device *vdev)
> > > vdev->priv = vi;
> > >
> > > INIT_WORK(&vi->config_work, virtnet_config_changed_work);
> > > + INIT_WORK(&vi->rx_mode_work, virtnet_rx_mode_work);
> > > spin_lock_init(&vi->refill_lock);
> > >
> > > if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
> > > @@ -4077,6 +4122,8 @@ static int virtnet_probe(struct virtio_device *vdev)
> > > if (vi->has_rss || vi->has_rss_hash_report)
> > > virtnet_init_default_rss(vi);
> > >
> > > + enable_rx_mode_work(vi);
> > > +
> > > /* serialize netdev register + virtio_device_ready() with ndo_open() */
> > > rtnl_lock();
> > >
> > > @@ -4174,6 +4221,8 @@ static void virtnet_remove(struct virtio_device *vdev)
> > >
> > > /* Make sure no work handler is accessing the device. */
> > > flush_work(&vi->config_work);
> > > + disable_rx_mode_work(vi);
> > > + flush_work(&vi->rx_mode_work);
> > >
> > > unregister_netdev(vi->dev);
> > >
> > > --
> > > 2.25.1
> >
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