Linux Virtualization - Mar 2019 - [PATCH] virtio_console: free unused buffers with virtio port

The commit a7a69ec0d8e4 ("virtio_console: free buffers after reset")
  deffered detaching of unused buffer to virtio device unplug time. 

  This causes unplug/replug of single port in virtio device with an 
  error "Error allocating inbufs\n". As we don't free the unused
buffers
  attached with the port. Re-plug the same port tries to allocate new
  buffers in virtqueue and results in this error if queue is full. 

  This patch removes the unused buffers in vq's when we unplug the port.
  This is the best we can do as we cannot call device_reset because virtio 
  device is still active. This was the working behaviour before the change 
  introduced in commit b3258ff1d6.

  Reported-by: Xiaohui Li <xiaohli at redhat.com>
  Fixes: b3258ff1d6 ("virtio_console: free buffers after reset")
  Signed-off-by: Pankaj Gupta <pagupta at redhat.com>
---
 drivers/char/virtio_console.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index fbeb71953526..5fbf2ac73111 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
 	kfree(port);
 }
 
+static void remove_unused_bufs(struct virtqueue *vq)
+{
+	struct port_buffer *buf;
+
+	while ((buf = virtqueue_detach_unused_buf(vq)))
+		free_buf(buf, true);
+}
+
 static void remove_port_data(struct port *port)
 {
 	spin_lock_irq(&port->inbuf_lock);
 	/* Remove unused data this port might have received. */
 	discard_port_data(port);
+	remove_unused_bufs(port->in_vq);
 	spin_unlock_irq(&port->inbuf_lock);
 
 	spin_lock_irq(&port->outvq_lock);
 	reclaim_consumed_buffers(port);
+	remove_unused_bufs(port->out_vq);
 	spin_unlock_irq(&port->outvq_lock);
 }
 
@@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device *portdev)
 	struct virtqueue *vq;
 
 	virtio_device_for_each_vq(portdev->vdev, vq) {
-		struct port_buffer *buf;
 
 		flush_bufs(vq, true);
-		while ((buf = virtqueue_detach_unused_buf(vq)))
-			free_buf(buf, true);
+		remove_unused_bufs(vq);
 	}
 	portdev->vdev->config->del_vqs(portdev->vdev);
 	kfree(portdev->in_vqs);
-- 
2.20.1

Adding Gal in CC [Forgot to add]
> 
> The commit a7a69ec0d8e4 ("virtio_console: free buffers after
reset")
>   deffered detaching of unused buffer to virtio device unplug time.
> 
>   This causes unplug/replug of single port in virtio device with an
>   error "Error allocating inbufs\n". As we don't free the
unused buffers
>   attached with the port. Re-plug the same port tries to allocate new
>   buffers in virtqueue and results in this error if queue is full.
> 
>   This patch removes the unused buffers in vq's when we unplug the
port.
>   This is the best we can do as we cannot call device_reset because virtio
>   device is still active. This was the working behaviour before the change
>   introduced in commit b3258ff1d6.
> 
>   Reported-by: Xiaohui Li <xiaohli at redhat.com>
>   Fixes: b3258ff1d6 ("virtio_console: free buffers after reset")
>   Signed-off-by: Pankaj Gupta <pagupta at redhat.com>
> ---
>  drivers/char/virtio_console.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index fbeb71953526..5fbf2ac73111 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
>          kfree(port);
>  }
>  
> +static void remove_unused_bufs(struct virtqueue *vq)
> +{
> +        struct port_buffer *buf;
> +
> +        while ((buf = virtqueue_detach_unused_buf(vq)))
> +                free_buf(buf, true);
> +}
> +
>  static void remove_port_data(struct port *port)
>  {
>          spin_lock_irq(&port->inbuf_lock);
>          /* Remove unused data this port might have received. */
>          discard_port_data(port);
> +        remove_unused_bufs(port->in_vq);
>          spin_unlock_irq(&port->inbuf_lock);
>  
>          spin_lock_irq(&port->outvq_lock);
>          reclaim_consumed_buffers(port);
> +        remove_unused_bufs(port->out_vq);
>          spin_unlock_irq(&port->outvq_lock);
>  }
>  
> @@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device *portdev)
>          struct virtqueue *vq;
>  
>          virtio_device_for_each_vq(portdev->vdev, vq) {
> -                struct port_buffer *buf;
>  
>                  flush_bufs(vq, true);
> -                while ((buf = virtqueue_detach_unused_buf(vq)))
> -                        free_buf(buf, true);
> +                remove_unused_bufs(vq);
>          }
>          portdev->vdev->config->del_vqs(portdev->vdev);
>          kfree(portdev->in_vqs);
> --
> 2.20.1
> 
>

On Mon, Mar 04, 2019 at 06:35:11PM +0530, Pankaj Gupta
wrote:
>   The commit a7a69ec0d8e4 ("virtio_console: free buffers after
reset")
>   deffered detaching of unused buffer to virtio device unplug time. 
> 
>   This causes unplug/replug of single port in virtio device with an 
>   error "Error allocating inbufs\n". As we don't free the
unused buffers
>   attached with the port. Re-plug the same port tries to allocate new
>   buffers in virtqueue and results in this error if queue is full. 
> 
>   This patch removes the unused buffers in vq's when we unplug the
port.
>   This is the best we can do as we cannot call device_reset because virtio 
>   device is still active. This was the working behaviour before the change 
>   introduced in commit b3258ff1d6.
> 
>   Reported-by: Xiaohui Li <xiaohli at redhat.com>
>   Fixes: b3258ff1d6 ("virtio_console: free buffers after reset")
>   Signed-off-by: Pankaj Gupta <pagupta at redhat.com>
I think if you do this you need to add support
in the packed ring.
> ---
>  drivers/char/virtio_console.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index fbeb71953526..5fbf2ac73111 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
>  	kfree(port);
>  }
>  
> +static void remove_unused_bufs(struct virtqueue *vq)
> +{
> +	struct port_buffer *buf;
> +
> +	while ((buf = virtqueue_detach_unused_buf(vq)))
> +		free_buf(buf, true);
> +}
> +
>  static void remove_port_data(struct port *port)
>  {
>  	spin_lock_irq(&port->inbuf_lock);
>  	/* Remove unused data this port might have received. */
>  	discard_port_data(port);
> +	remove_unused_bufs(port->in_vq);
>  	spin_unlock_irq(&port->inbuf_lock);
>  
>  	spin_lock_irq(&port->outvq_lock);
>  	reclaim_consumed_buffers(port);
> +	remove_unused_bufs(port->out_vq);
>  	spin_unlock_irq(&port->outvq_lock);
>  }
>  
> @@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device *portdev)
>  	struct virtqueue *vq;
>  
>  	virtio_device_for_each_vq(portdev->vdev, vq) {
> -		struct port_buffer *buf;
>  
>  		flush_bufs(vq, true);
> -		while ((buf = virtqueue_detach_unused_buf(vq)))
> -			free_buf(buf, true);
> +		remove_unused_bufs(vq);
>  	}
>  	portdev->vdev->config->del_vqs(portdev->vdev);
>  	kfree(portdev->in_vqs);
> -- 
> 2.20.1

Hello Michael,

Thanks for your reply.
> 
> On Mon, Mar 04, 2019 at 06:35:11PM +0530, Pankaj Gupta wrote:
> >   The commit a7a69ec0d8e4 ("virtio_console: free buffers after
reset")
> >   deffered detaching of unused buffer to virtio device unplug time.
> > 
> >   This causes unplug/replug of single port in virtio device with an
> >   error "Error allocating inbufs\n". As we don't free
the unused buffers
> >   attached with the port. Re-plug the same port tries to allocate new
> >   buffers in virtqueue and results in this error if queue is full.
> > 
> >   This patch removes the unused buffers in vq's when we unplug the
port.
> >   This is the best we can do as we cannot call device_reset because
virtio
> >   device is still active. This was the working behaviour before the
change
> >   introduced in commit b3258ff1d6.
> > 
> >   Reported-by: Xiaohui Li <xiaohli at redhat.com>
> >   Fixes: b3258ff1d6 ("virtio_console: free buffers after
reset")
> >   Signed-off-by: Pankaj Gupta <pagupta at redhat.com>
> 
> I think if you do this you need to add support
> in the packed ring.
o.k. I will look at the implementation details for "support
of packed ring" for virtio_console. This will take some time.

Meanwhile "virtio_console" port hotplug/unplug is broken in upstream.
Can we accept this patch as it fixes the upstream and together
with parent patch(b3258ff1d6) does nice cleanups as well.

Thanks,
Pankaj  
> 
> > ---
> >  drivers/char/virtio_console.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/char/virtio_console.c
b/drivers/char/virtio_console.c
> > index fbeb71953526..5fbf2ac73111 100644
> > --- a/drivers/char/virtio_console.c
> > +++ b/drivers/char/virtio_console.c
> > @@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
> >          kfree(port);
> >  }
> >  
> > +static void remove_unused_bufs(struct virtqueue *vq)
> > +{
> > +        struct port_buffer *buf;
> > +
> > +        while ((buf = virtqueue_detach_unused_buf(vq)))
> > +                free_buf(buf, true);
> > +}
> > +
> >  static void remove_port_data(struct port *port)
> >  {
> >          spin_lock_irq(&port->inbuf_lock);
> >          /* Remove unused data this port might have received. */
> >          discard_port_data(port);
> > +        remove_unused_bufs(port->in_vq);
> >          spin_unlock_irq(&port->inbuf_lock);
> >  
> >          spin_lock_irq(&port->outvq_lock);
> >          reclaim_consumed_buffers(port);
> > +        remove_unused_bufs(port->out_vq);
> >          spin_unlock_irq(&port->outvq_lock);
> >  }
> >  
> > @@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device
*portdev)
> >          struct virtqueue *vq;
> >  
> >          virtio_device_for_each_vq(portdev->vdev, vq) {
> > -                struct port_buffer *buf;
> >  
> >                  flush_bufs(vq, true);
> > -                while ((buf = virtqueue_detach_unused_buf(vq)))
> > -                        free_buf(buf, true);
> > +                remove_unused_bufs(vq);
> >          }
> >          portdev->vdev->config->del_vqs(portdev->vdev);
> >          kfree(portdev->in_vqs);
> > --
> > 2.20.1
>

> 
> The commit a7a69ec0d8e4 ("virtio_console: free buffers after
reset")
>   deffered detaching of unused buffer to virtio device unplug time.
> 
>   This causes unplug/replug of single port in virtio device with an
>   error "Error allocating inbufs\n". As we don't free the
unused buffers
>   attached with the port. Re-plug the same port tries to allocate new
>   buffers in virtqueue and results in this error if queue is full.
> 
>   This patch removes the unused buffers in vq's when we unplug the
port.
>   This is the best we can do as we cannot call device_reset because virtio
>   device is still active. This was the working behaviour before the change
>   introduced in commit b3258ff1d6.
ping.

This patch fixes a regression in upstream kernel, virtio_console driver.
Can we please have this merged.

Thanks,
Pankaj
> 
>   Reported-by: Xiaohui Li <xiaohli at redhat.com>
>   Fixes: b3258ff1d6 ("virtio_console: free buffers after reset")
>   Signed-off-by: Pankaj Gupta <pagupta at redhat.com>
> ---
>  drivers/char/virtio_console.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index fbeb71953526..5fbf2ac73111 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
>  	kfree(port);
>  }
>  
> +static void remove_unused_bufs(struct virtqueue *vq)
> +{
> +	struct port_buffer *buf;
> +
> +	while ((buf = virtqueue_detach_unused_buf(vq)))
> +		free_buf(buf, true);
> +}
> +
>  static void remove_port_data(struct port *port)
>  {
>  	spin_lock_irq(&port->inbuf_lock);
>  	/* Remove unused data this port might have received. */
>  	discard_port_data(port);
> +	remove_unused_bufs(port->in_vq);
>  	spin_unlock_irq(&port->inbuf_lock);
>  
>  	spin_lock_irq(&port->outvq_lock);
>  	reclaim_consumed_buffers(port);
> +	remove_unused_bufs(port->out_vq);
>  	spin_unlock_irq(&port->outvq_lock);
>  }
>  
> @@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device *portdev)
>  	struct virtqueue *vq;
>  
>  	virtio_device_for_each_vq(portdev->vdev, vq) {
> -		struct port_buffer *buf;
>  
>  		flush_bufs(vq, true);
> -		while ((buf = virtqueue_detach_unused_buf(vq)))
> -			free_buf(buf, true);
> +		remove_unused_bufs(vq);
>  	}
>  	portdev->vdev->config->del_vqs(portdev->vdev);
>  	kfree(portdev->in_vqs);
> --
> 2.20.1
> 
>

On Mon, Mar 11, 2019 at 01:58:11AM -0400, Pankaj Gupta
wrote:
> 
> > 
> > The commit a7a69ec0d8e4 ("virtio_console: free buffers after
reset")
> >   deffered detaching of unused buffer to virtio device unplug time.
> > 
> >   This causes unplug/replug of single port in virtio device with an
> >   error "Error allocating inbufs\n". As we don't free
the unused buffers
> >   attached with the port. Re-plug the same port tries to allocate new
> >   buffers in virtqueue and results in this error if queue is full.
> > 
> >   This patch removes the unused buffers in vq's when we unplug the
port.
> >   This is the best we can do as we cannot call device_reset because
virtio
> >   device is still active. This was the working behaviour before the
change
> >   introduced in commit b3258ff1d6.
> 
> ping.
> 
> This patch fixes a regression in upstream kernel, virtio_console driver.
> Can we please have this merged.
> 
> Thanks,
> Pankaj
Sorry, no, I don't think that's a full fix.
> > 
> >   Reported-by: Xiaohui Li <xiaohli at redhat.com>
> >   Fixes: b3258ff1d6 ("virtio_console: free buffers after
reset")
> >   Signed-off-by: Pankaj Gupta <pagupta at redhat.com>
> > ---
> >  drivers/char/virtio_console.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/char/virtio_console.c
b/drivers/char/virtio_console.c
> > index fbeb71953526..5fbf2ac73111 100644
> > --- a/drivers/char/virtio_console.c
> > +++ b/drivers/char/virtio_console.c
> > @@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
> >  	kfree(port);
> >  }
> >  
> > +static void remove_unused_bufs(struct virtqueue *vq)
> > +{
> > +	struct port_buffer *buf;
> > +
> > +	while ((buf = virtqueue_detach_unused_buf(vq)))
> > +		free_buf(buf, true);
> > +}
> > +
> >  static void remove_port_data(struct port *port)
> >  {
> >  	spin_lock_irq(&port->inbuf_lock);
> >  	/* Remove unused data this port might have received. */
> >  	discard_port_data(port);
> > +	remove_unused_bufs(port->in_vq);
> >  	spin_unlock_irq(&port->inbuf_lock);
> >  
> >  	spin_lock_irq(&port->outvq_lock);
> >  	reclaim_consumed_buffers(port);
> > +	remove_unused_bufs(port->out_vq);
> >  	spin_unlock_irq(&port->outvq_lock);
> >  }
> >  
> > @@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device
*portdev)
> >  	struct virtqueue *vq;
> >  
> >  	virtio_device_for_each_vq(portdev->vdev, vq) {
> > -		struct port_buffer *buf;
> >  
> >  		flush_bufs(vq, true);
> > -		while ((buf = virtqueue_detach_unused_buf(vq)))
> > -			free_buf(buf, true);
> > +		remove_unused_bufs(vq);
> >  	}
> >  	portdev->vdev->config->del_vqs(portdev->vdev);
> >  	kfree(portdev->in_vqs);
> > --
> > 2.20.1
> > 
> >