Some virtio PCI devices can change the device configuration state, as
reflected in the device-specific configuration region of the device. In
this case:
* If MSI-X capability is disabled:
1. Set the second lower bit of the ISR Status field for the device
2. Send the appropriate PCI interrupt for the device.
* If MSI-X capability is enabled:
1. If config_msix_vector is not NO_VECTOR, request the appropriate
MSI-X interrupt message for the device, config_msix_vector sets
the MSI-X Table entry number.
A single interrupt MAY indicate both that one or more virtqueue has been
used and that the configuration space has changed.
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Reviewed-by: Hao Li <hao.l.li@intel.com>
