On Fri, Sep 10, 2021 at 4:03 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > On Fri, Sep 10, 2021, Peter Gonda wrote: > > > Do we really want to bury this under KVM_CAP? Even KVM_CAP_VM_COPY_ENC_CONTEXT_FROM > > > is a bit of a stretch, but at least that's a one-way "enabling", whereas this > > > migration routine should be able to handle multiple migrations, e.g. migrate A->B > > > and B->A. Peeking at your selftest, it should be fairly easy to add in this edge > > > case. > > > > > > This is probably a Paolo question, I've no idea if there's a desire to expand > > > KVM_CAP versus adding a new ioctl(). > > > > Thanks for the review Sean. I put this under KVM_CAP as you suggested > > following the idea of svm_vm_copy_asid_from. Paolo or anyone else have > > thoughts here? It doesn't really matter to me. > > Ah, sorry :-/ I obviously don't have a strong preference either. I am going to suggest leaving it under KVM_CAP for this reason. I don't see a great use case for A->B then B->A migrations. And if we are going to move to dst must be not SEV or SEV-ES enabled, which I think makes sense. Then your VM can only ever have migrated from 1 other VM since once it has it will be SEV/SEV-ES enabled. Does that seem reasonable? > > > > > +Architectures: x86 SEV enabled > > > > +Type: vm > > > > +Parameters: args[0] is the fd of the source vm > > > > +Returns: 0 on success > > > > > > It'd be helpful to provide a brief description of the error cases. Looks like > > > -EINVAL is the only possible error? > > > > > > > +This capability enables userspace to migrate the encryption context > > > > > > I would prefer to scope this beyond "encryption context". Even for SEV, it > > > copies more than just the "context", which was an abstraction of SEV's ASID, > > > e.g. this also hands off the set of encrypted memory regions. Looking toward > > > the future, if TDX wants to support this it's going to need to hand over a ton > > > of stuff, e.g. S-EPT tables. > > > > > > Not sure on a name, maybe MIGRATE_PROTECTED_VM_FROM? > > > > Protected VM sounds reasonable. I was using 'context' here to mean all > > metadata related to a CoCo VM as with the > > KVM_CAP_VM_COPY_ENC_CONTEXT_FROM. Is it worth diverging naming here? > > Yes, as they are two similar but slightly different things, IMO we want to diverge > so that it's obvious they operate on different data. Sounds good I'll rename.
