On Thu, Nov 13, 2025 at 11:09:32AM -0500, Michael S. Tsirkin wrote: > On Fri, Nov 07, 2025 at 10:01:49AM +0800, Jason Wang wrote: > > We used to clear features silently in virtio_net_get_features() even > > if it is required. This complicates the live migration compatibility > > as the management layer may think the feature is enabled but in fact > > not. > > > > Let's add a strict feature check to make sure if there's a mismatch > > between the required feature and peer, fail the get_features() > > immediately instead of waiting until the migration to fail. This > > offload the migration compatibility completely to the management > > layer. > > > > Signed-off-by: Jason Wang <[email protected]> > > This is not really useful - how do users know how to tweak their > command lines? > We discussed this many times. > To try and solve this you need a tool that will tell you how to start > VM on X to make it migrateable to Y or Z. > > > More importantly, > migration is a niche thing and breaking booting perfectly good VMs > just for that seems wrong.
IMHO Jason's proposal is useful in that it now provides a way to provide ABI stablility but allows auto-ON to exist. If we think migration is optional, we could add a migration blocker where strict check flag is set to OFF, as I mentioned in the email reply to Dan. As that implies the VM ABI is not guaranteed. Thanks, > > > If you want to keep this off by default, and have management > enable this if it knows what it's doing, then I don't really > care. -- Peter Xu
