On Thu, Jul 11, 2024 at 03:09:28PM +0000, Wang, Wei W wrote: > On Thursday, July 11, 2024 10:14 PM, Daniel P. Berrangé wrote: > > On Thu, Jul 11, 2024 at 02:13:31PM +0000, Wang, Wei W wrote: > > > On Thursday, July 11, 2024 8:25 PM, Daniel P. Berrangé wrote: > > > > On Thu, Jul 11, 2024 at 12:10:34PM +0000, Wang, Wei W wrote: > > > > > On Thursday, July 11, 2024 7:48 PM, Daniel P. Berrangé wrote: > > > > > > On Wed, Jul 03, 2024 at 10:49:12PM +0800, Wei Wang wrote: > > > > > AFAIK, many users are not aware of this, and also we couldn't > > > > > assume everybody knows it. That's why we want to add the enforcement. > > > > > > > > Users who directly launch QEMU are expected to know about QEMU > > > > config details for migration. If they don't, then they ought to be > > > > using a higher level tool like libvirt, which ensures the configuration > > > > is > > migration compatible. > > > > > > Agree that libvirt has this advantage and is more user friendly. But > > > it doesn't seem to solve the issue mentioned by this patch - if users > > > don't > > explicitly set "enforce=true" > > > in libvirt configs for the guest, then migrating the guest across > > > hosts with different features could still be risky. Unless there is > > > similar enforcement in libvirt to require users to set "enforce=true" for > > > the > > guest to be migratable. > > > > Yes, libvirt takes steps to ensure CPU compatibility before migrating. > > Thanks for sharing, but curious about those steps. For example, with > "enforce=off" > (by default), features on the destination could be filtered by QEMU (kind of > silently, > just has warning logs). > How would the source side libvirt get informed about more features getting > filtered by > the destination side QEMU (as the destination host has less support for this > vcpu model)? > This causes inconsistencies.
Libvirt queries QEMU to ask it what features were actually active in the guest. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
