RE: [virtio-comment] Re: [PATCH v1 3/8] device-context: Define the device context fields for device migration

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Wednesday, October 25, 2023 3:50 PM
> 
> On Wed, Oct 25, 2023 at 09:50:02AM +0000, Parav Pandit wrote:
> > Hence, I believe device context as defined now is still reusable as common
> building block.
> > For non-passthrough, such hypervisor can simply ignore the fields which it is
> not interested in.
> 
> Interesting. So a hypervisor encounters a field it does not recognize. How does
> hypervisor know that a field is safe to ignore?

In v2 all the supported fields are published in a query command.
If hypervisor wants to know the precise fields of interest, when the device reports unknown field, it can make its decision to ignore or fail to work.