On Wed, Oct 04, 2023 at 07:51:17AM -0700, Sean Christopherson wrote: > KVM's ABI has no formal notion of guest boot=>shutdown or live migration. The > myriad KVM_GET_* APIs allow taking a snapshot of guest state, and the KVM_SET_* > APIs allow loading a snapshot of guest state. Live migration is probably the most > common use of those APIs, but there are other use cases. I think the lightbulb just clicked, it is really this: > No, the VM will not have less features, because KVM_SET_XSAVE loads *data*, not > features [...] I think I'm conflating the data vs. features aspect here and will have to revisit my understanding of the code... > > Ultimately, this problem is not really fixable if said features cannot be > > removed. > It's not about removing features. The change you're asking for is to have KVM > *silently* drop data. Aside from the fact that such a change would break KVM's > ABI, silently ignoring data that userspace has explicitly requested be loaded for > a vCPU is incredibly dangerous. Sorry if it came off that way - I fully understand and am resigned to the "you break it, you keep both halves" nature of what I had initially proposed and that it is not a generally tractable solution. That being said, I genuinely appreciate your jump to action on this problem! Thanks, Tyler
