On Thu, Apr 15, 2021 at 08:14:30PM +0100, Dr. David Alan Gilbert wrote: > * Paolo Bonzini (pbonz...@redhat.com) wrote: > > On 06/04/21 13:42, Vitaly Kuznetsov wrote: > > > older machine types are still available (I disable it for <= 5.1 but we > > > can consider disabling it for 5.2 too). The feature is upstream since > > > Linux 5.8, I know that QEMU supports much older kernels but this doesn't > > > probably mean that we can't enable new KVM PV features unless all > > > supported kernels have it, we'd have to wait many years otherwise. > > > > Yes, this is a known problem in fact. :( In 6.0 we even support RHEL 7, > > though that will go away in 6.1. > > > > We should take the occasion of dropping RHEL7 to be clearer about which > > kernels are supported. > > It would be nice to be able to define sets of KVM functonality that we > can either start given machine types with, or provide a separate switch > to limit kvm functionality back to some defined point. We do trip over > the same things pretty regularly when accidentally turning on new > features.
The same idea can apply to the hyperv=on stuff Vitaly is working on. Maybe we should consider making a generic version of the s390x FeatGroup code, use it to define convenient sets of KVM and hyperv features. -- Eduardo
