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

On Thu, Dec 16, 2021 at 1:27 AM Mikhail Golubev [off-list ref] wrote:

The 12/14/2021 18:26, Michael S. Tsirkin wrote:

quoted

On Tue, Dec 14, 2021 at 05:33:05PM +0100, Mikhail Golubev wrote:

quoted

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 <redacted>

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

quoted

quoted

---
 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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