Messages in this thread | | | Date | Tue, 27 Apr 2021 22:14:05 +0000 | From | Sean Christopherson <> | Subject | Re: [PATCH v2 2/2] KVM: x86: add MSR_KVM_MIGRATION_CONTROL |
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On Wed, Apr 21, 2021, Paolo Bonzini wrote: > Add a new MSR that can be used to communicate whether the page > encryption status bitmap is up to date and therefore whether live > migration of an encrypted guest is possible. > > The MSR should be processed by userspace if it is going to live > migrate the guest; the default implementation does nothing. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > ---
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> @@ -91,6 +93,8 @@ struct kvm_clock_pairing { > /* MSR_KVM_ASYNC_PF_INT */ > #define KVM_ASYNC_PF_VEC_MASK GENMASK(7, 0) > > +/* MSR_KVM_MIGRATION_CONTROL */ > +#define KVM_PAGE_ENC_STATUS_UPTODATE (1 << 0)
Why explicitly tie this to encryption status? AFAICT, doing so serves no real purpose and can only hurt us in the long run. E.g. if a new use case for "disabling" migration comes along and it has nothing to do with encryption, then it has the choice of either using a different bit or bastardizing the existing control.
I've no idea if such a use case is remotely likely to pop up, but allowing for such a possibility costs us nothing.
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