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

    --

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