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

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