vdpa-dev: Fix the issue of device status not updating when configuration interruption...

vdpa-dev: Fix the issue of device status not updating when configuration interruption is triggered

The set_config callback function vhost_vdpa_device_get_config in
vdpa-dev does not fetch the current device status from the hardware
device, causing the guest os to not receive the latest device status
information.

The hardware updates the config status of the vdpa device and then
notifies the os. The guest os receives an interrupt notification,
triggering a get_config access in the kernel, which then enters qemu
internally. Ultimately, the vhost_vdpa_device_get_config function of
vdpa-dev is called

One scenario encountered is when the device needs to bring down the
vdpa net device. After modifying the status field of virtio_net_config
in the hardware, it sends an interrupt notification. However, the guest
os always receives the STATUS field as VIRTIO_NET_S_LINK_UP.

Signed-off-by: Yuxue Liu <yuxue.liu@jaguarmicro.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20240408020003.1979-1-yuxue.liu@jaguarmicro.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 6ae72f609a21cfc56bf655cd4bcded5d07691ce7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>