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

--

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