[RFC PATCH] virtio: do not reset stateful devices on resume

[RFC PATCH] virtio: do not reset stateful devices on resume

[Mikhail Golubev]

From: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>

We assume that stateful devices can maintain their state while
suspended. And for this reason they don't have a freeze callback. If
such a device is reset during resume, the device state/context will be
lost on the device side. And the virtual device will stop working.

Signed-off-by: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
Signed-off-by: Mikhail Golubev <mikhail.golubev@opensynergy.com>
---
 drivers/virtio/virtio.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 236081afe9a2..defa15b56eb8 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -472,6 +472,13 @@ int virtio_device_restore(struct virtio_device *dev)
 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
 	int ret;
 
+	/* Short path for stateful devices. Here we assume that if the device
+	 * does not have a freeze callback, its state was not changed when
+	 * suspended.
+	 */
+	if (drv && !drv->freeze)
+		goto on_config_enable;
+
 	/* We always start by resetting the device, in case a previous
 	 * driver messed it up. */
 	dev->config->reset(dev);
@@ -503,6 +510,7 @@ int virtio_device_restore(struct virtio_device *dev)
 	/* Finally, tell the device we're all set */
 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
 
+on_config_enable:
 	virtio_config_enable(dev);
 
 	return 0;
-- 
2.34.1


-- 

Re: [RFC PATCH] virtio: do not reset stateful devices on resume

[Michael S. Tsirkin]

On Tue, Dec 14, 2021 at 05:33:05PM +0100, Mikhail Golubev wrote:
> From: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
> 
> We assume that stateful devices can maintain their state while
> suspended. And for this reason they don't have a freeze callback. If
> such a device is reset during resume, the device state/context will be
> lost on the device side. And the virtual device will stop working.
> 
> Signed-off-by: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
> Signed-off-by: Mikhail Golubev <mikhail.golubev@opensynergy.com>

A bit more specific? Which configs does this patch fix?

> ---
>  drivers/virtio/virtio.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 236081afe9a2..defa15b56eb8 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -472,6 +472,13 @@ int virtio_device_restore(struct virtio_device *dev)
>  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
>  	int ret;
>  
> +	/* Short path for stateful devices. Here we assume that if the device
> +	 * does not have a freeze callback, its state was not changed when
> +	 * suspended.
> +	 */
> +	if (drv && !drv->freeze)
> +		goto on_config_enable;
> +
>  	/* We always start by resetting the device, in case a previous
>  	 * driver messed it up. */
>  	dev->config->reset(dev);
> @@ -503,6 +510,7 @@ int virtio_device_restore(struct virtio_device *dev)
>  	/* Finally, tell the device we're all set */
>  	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
>  
> +on_config_enable:
>  	virtio_config_enable(dev);
>  
>  	return 0;
> -- 
> 2.34.1
> 
> 
> -- 

Re: [RFC PATCH] virtio: do not reset stateful devices on resume

[Mikhail Golubev]

The 12/14/2021 18:26, Michael S. Tsirkin wrote:
> On Tue, Dec 14, 2021 at 05:33:05PM +0100, Mikhail Golubev wrote:
> > From: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
> > 
> > We assume that stateful devices can maintain their state while
> > suspended. And for this reason they don't have a freeze callback. If
> > such a device is reset during resume, the device state/context will be
> > lost on the device side. And the virtual device will stop working.
> > 
> > Signed-off-by: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
> > Signed-off-by: Mikhail Golubev <mikhail.golubev@opensynergy.com>
> 
> A bit more specific? Which configs does this patch fix?

We had encountered an issue related to 'stateful' GPU 3d (virglrenderer) and
video (gstreamer) devices.

BR,
Mikhail

> 
> > ---
> >  drivers/virtio/virtio.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> > index 236081afe9a2..defa15b56eb8 100644
> > --- a/drivers/virtio/virtio.c
> > +++ b/drivers/virtio/virtio.c
> > @@ -472,6 +472,13 @@ int virtio_device_restore(struct virtio_device *dev)
> >  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
> >  	int ret;
> >  
> > +	/* Short path for stateful devices. Here we assume that if the device
> > +	 * does not have a freeze callback, its state was not changed when
> > +	 * suspended.
> > +	 */
> > +	if (drv && !drv->freeze)
> > +		goto on_config_enable;
> > +
> >  	/* We always start by resetting the device, in case a previous
> >  	 * driver messed it up. */
> >  	dev->config->reset(dev);
> > @@ -503,6 +510,7 @@ int virtio_device_restore(struct virtio_device *dev)
> >  	/* Finally, tell the device we're all set */
> >  	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
> >  
> > +on_config_enable:
> >  	virtio_config_enable(dev);
> >  
> >  	return 0;
> > -- 
> > 2.34.1
> > 
> > 
> > -- 
> 

-- 

Re: [RFC PATCH] virtio: do not reset stateful devices on resume

[Jason Wang]

On Thu, Dec 16, 2021 at 1:27 AM Mikhail Golubev <mgo@opensynergy.com> wrote:
>
> The 12/14/2021 18:26, Michael S. Tsirkin wrote:
> > On Tue, Dec 14, 2021 at 05:33:05PM +0100, Mikhail Golubev wrote:
> > > From: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
> > >
> > > We assume that stateful devices can maintain their state while
> > > suspended. And for this reason they don't have a freeze callback. If
> > > such a device is reset during resume, the device state/context will be
> > > lost on the device side. And the virtual device will stop working.
> > >
> > > Signed-off-by: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
> > > Signed-off-by: Mikhail Golubev <mikhail.golubev@opensynergy.com>
> >
> > A bit more specific? Which configs does this patch fix?
>
> We had encountered an issue related to 'stateful' GPU 3d (virglrenderer) and
> video (gstreamer) devices.

Adding Gerd and Stefan.

I wonder if we suffer from a similar issue with virtio-fs.

Thanks

>
> BR,
> Mikhail
>
> >
> > > ---
> > >  drivers/virtio/virtio.c | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > >
> > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> > > index 236081afe9a2..defa15b56eb8 100644
> > > --- a/drivers/virtio/virtio.c
> > > +++ b/drivers/virtio/virtio.c
> > > @@ -472,6 +472,13 @@ int virtio_device_restore(struct virtio_device *dev)
> > >     struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
> > >     int ret;
> > >
> > > +   /* Short path for stateful devices. Here we assume that if the device
> > > +    * does not have a freeze callback, its state was not changed when
> > > +    * suspended.
> > > +    */
> > > +   if (drv && !drv->freeze)
> > > +           goto on_config_enable;
> > > +
> > >     /* We always start by resetting the device, in case a previous
> > >      * driver messed it up. */
> > >     dev->config->reset(dev);
> > > @@ -503,6 +510,7 @@ int virtio_device_restore(struct virtio_device *dev)
> > >     /* Finally, tell the device we're all set */
> > >     virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
> > >
> > > +on_config_enable:
> > >     virtio_config_enable(dev);
> > >
> > >     return 0;
> > > --
> > > 2.34.1
> > >
> > >
> > > --
> >
>
> --
>