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Date: Fri, 5 May 2023 11:46:06 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Michael S. Tsirkin" <mst@...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
在 2023/4/17 11:40, Jason Wang 写道:
> On Fri, Apr 14, 2023 at 3:21 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>> 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?
> It doesn't look easy since we are drivers for virtio bus. Underlayer
> details were hidden from virtio-net.
>
> Or do you have any ideas on this?
Michael, any thought on this?
Thanks
>
> Thanks
>
>>>>
>>>>> ---
>>>>> 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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