Messages in this thread | | | From | Steve Rutherford <> | Date | Wed, 24 Feb 2021 19:55:51 -0800 | Subject | Re: [RFC] KVM: x86: Support KVM VMs sharing SEV context |
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On Wed, Feb 24, 2021 at 9:37 AM Sean Christopherson <seanjc@google.com> wrote: > > + unsigned int asid; > > + int ret; > > + > > + if (!sev_guest(kvm)) > > + return -ENOTTY; > > + > > + mutex_lock(&kvm->lock); > > + > > + /* Mirrors of mirrors should work, but let's not get silly */ > > Do we really care? Yes, unless you reparent mirrors of mirrors to the original ASID owner. If you don't do that, I think userspace could pump a chain of mirrors to blow the kernel stack when it closes the leaf vm, since you could build up a chain of sev_vm_destroys. Refcounting the ASIDs directly would also fix this.
Nate's early implementation did the reparenting, but I pushed for the simplification since it made the locking a bit hairy. > > > + if (is_mirroring_enc_context(kvm)) { > > + ret = -ENOTTY; > > + goto failed; > > + } > > +
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