Linux Virtualization - Oct 2013 - [PATCH net 1/2] virtio-net: don't respond to cpu hotplug notifier if we're not ready

We're trying to re-configure the affinity unconditionally in cpu hotplug
callback. This may lead the issue during resuming from s3/s4 since

- virt queues haven't been allocated at that time.
- it's unnecessary since thaw method will re-configure the affinity.

Fix this issue by checking the config_enable and do nothing is we're not
ready.

The bug were introduced by commit 8de4b2f3ae90c8fc0f17eeaab87d5a951b66ee17
(virtio-net: reset virtqueue affinity when doing cpu hotplug).

Cc: Rusty Russell <rusty at rustcorp.com.au>
Cc: Michael S. Tsirkin <mst at redhat.com>
Cc: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
The patch is need for 3.8 and above.
---
 drivers/net/virtio_net.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index defec2b..c4bc1cc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1116,6 +1116,11 @@ static int virtnet_cpu_callback(struct notifier_block
*nfb,
 {
 	struct virtnet_info *vi = container_of(nfb, struct virtnet_info, nb);
 
+	mutex_lock(&vi->config_lock);
+
+	if (!vi->config_enable)
+		goto done;
+
 	switch(action & ~CPU_TASKS_FROZEN) {
 	case CPU_ONLINE:
 	case CPU_DOWN_FAILED:
@@ -1128,6 +1133,9 @@ static int virtnet_cpu_callback(struct notifier_block
*nfb,
 	default:
 		break;
 	}
+
+done:
+	mutex_unlock(&vi->config_lock);
 	return NOTIFY_OK;
 }
 
-- 
1.8.1.2

We used to schedule the refill work unconditionally after changing the
number of queues. This may lead an issue if the device is not
up. Since we only try to cancel the work in ndo_stop(), this may cause
the refill work still work after removing the device. Fix this by only
schedule the work when device is up.

The bug were introduce by commit 9b9cd8024a2882e896c65222aa421d461354e3f2.
(virtio-net: fix the race between channels setting and refill)

Cc: Rusty Russell <rusty at rustcorp.com.au>
Cc: Michael S. Tsirkin <mst at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
The patch were need for 3.10 and above.
---
 drivers/net/virtio_net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c4bc1cc..92f0096 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -938,7 +938,9 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16
queue_pairs)
 		return -EINVAL;
 	} else {
 		vi->curr_queue_pairs = queue_pairs;
-		schedule_delayed_work(&vi->refill, 0);
+		/* virtnet_open() will refill when device is going to up. */
+		if (dev->flags & IFF_UP)
+			schedule_delayed_work(&vi->refill, 0);
 	}
 
 	return 0;
-- 
1.8.1.2

On Mon, Oct 14, 2013 at 05:56:34PM +0800, Jason Wang
wrote:
> We're trying to re-configure the affinity unconditionally in cpu
hotplug
> callback. This may lead the issue during resuming from s3/s4 since
> 
> - virt queues haven't been allocated at that time.
> - it's unnecessary since thaw method will re-configure the affinity.
> 
> Fix this issue by checking the config_enable and do nothing is we're
not ready.
> 
> The bug were introduced by commit 8de4b2f3ae90c8fc0f17eeaab87d5a951b66ee17
> (virtio-net: reset virtqueue affinity when doing cpu hotplug).
> 
> Cc: Rusty Russell <rusty at rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst at redhat.com>
> Cc: Wanlong Gao <gaowanlong at cn.fujitsu.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>
> ---
> The patch is need for 3.8 and above.
> ---
>  drivers/net/virtio_net.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index defec2b..c4bc1cc 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1116,6 +1116,11 @@ static int virtnet_cpu_callback(struct
notifier_block *nfb,
>  {
>  	struct virtnet_info *vi = container_of(nfb, struct virtnet_info, nb);
>  
> +	mutex_lock(&vi->config_lock);
> +
> +	if (!vi->config_enable)
> +		goto done;
> +
>  	switch(action & ~CPU_TASKS_FROZEN) {
>  	case CPU_ONLINE:
>  	case CPU_DOWN_FAILED:
> @@ -1128,6 +1133,9 @@ static int virtnet_cpu_callback(struct notifier_block
*nfb,
>  	default:
>  		break;
>  	}
> +
> +done:
> +	mutex_unlock(&vi->config_lock);
>  	return NOTIFY_OK;
>  }
>  
> -- 
> 1.8.1.2

On Mon, Oct 14, 2013 at 05:56:35PM +0800, Jason Wang
wrote:
> We used to schedule the refill work unconditionally after changing the
> number of queues. This may lead an issue if the device is not
> up. Since we only try to cancel the work in ndo_stop(), this may cause
> the refill work still work after removing the device. Fix this by only
> schedule the work when device is up.
> 
> The bug were introduce by commit 9b9cd8024a2882e896c65222aa421d461354e3f2.
> (virtio-net: fix the race between channels setting and refill)
> 
> Cc: Rusty Russell <rusty at rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst at redhat.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
It bothers me that we look at the flag without any
locks here.
I think we'll need to take the rtnl lock at least
on restore.
> ---
> The patch were need for 3.10 and above.
> ---
>  drivers/net/virtio_net.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c4bc1cc..92f0096 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -938,7 +938,9 @@ static int virtnet_set_queues(struct virtnet_info *vi,
u16 queue_pairs)
>  		return -EINVAL;
>  	} else {
>  		vi->curr_queue_pairs = queue_pairs;
> -		schedule_delayed_work(&vi->refill, 0);
> +		/* virtnet_open() will refill when device is going to up. */
> +		if (dev->flags & IFF_UP)
> +			schedule_delayed_work(&vi->refill, 0);
>  	}
>  
>  	return 0;
> -- 
> 1.8.1.2

On 10/14/2013 05:56 PM, Jason Wang wrote:
> We're trying to re-configure the affinity unconditionally in cpu
hotplug
> callback. This may lead the issue during resuming from s3/s4 since
> 
> - virt queues haven't been allocated at that time.
> - it's unnecessary since thaw method will re-configure the affinity.
> 
> Fix this issue by checking the config_enable and do nothing is we're
not ready.
> 
> The bug were introduced by commit 8de4b2f3ae90c8fc0f17eeaab87d5a951b66ee17
> (virtio-net: reset virtqueue affinity when doing cpu hotplug).
> 
> Cc: Rusty Russell <rusty at rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst at redhat.com>
> Cc: Wanlong Gao <gaowanlong at cn.fujitsu.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Thank you.

Reviewed-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>

> ---
> The patch is need for 3.8 and above.
> ---
>  drivers/net/virtio_net.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index defec2b..c4bc1cc 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1116,6 +1116,11 @@ static int virtnet_cpu_callback(struct
notifier_block *nfb,
>  {
>  	struct virtnet_info *vi = container_of(nfb, struct virtnet_info, nb);
>  
> +	mutex_lock(&vi->config_lock);
> +
> +	if (!vi->config_enable)
> +		goto done;
> +
>  	switch(action & ~CPU_TASKS_FROZEN) {
>  	case CPU_ONLINE:
>  	case CPU_DOWN_FAILED:
> @@ -1128,6 +1133,9 @@ static int virtnet_cpu_callback(struct notifier_block
*nfb,
>  	default:
>  		break;
>  	}
> +
> +done:
> +	mutex_unlock(&vi->config_lock);
>  	return NOTIFY_OK;
>  }
>  
>