RE: [virtio-comment] [PATCH v1 1/8] admin: Add theory of operation for device migration

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Thursday, November 16, 2023 11:53 AM
> 
> On Thu, Nov 16, 2023 at 05:28:19AM +0000, Parav Pandit wrote:
> > You continue to want to overload admin commands for dual purpose, does
> not make sense to me.
> 
> dual -> as a transport and for migration? why can't they be used for this? I was
> really hoping to cover these two cases when I proposed them.
For following reasons.

1. migration needs incremental reads of only changed context between two reads

2. migration writes covers large part of the configurations not just virtio common config and device config.
Such as configuration occurred through the CVQ. All of these is not needed when done from guest directly via member's own CVQ.

For backward compatible SIOV transport, one may need them to transport without above two properties.

3. None of this transport is needed for PFs, VFs and non-backward compatible SIOVs.
Each device to have its own transport that is not intercepted by the hypervisor and follow the equivalency principle uniformly for all 3 device types.