Re: [PATCH v3 03/37] KVM: nVMX: Invalidate all EPTP contexts when emulating INVEPT for L1

[Jim Mattson]

On Fri, Mar 20, 2020 at 2:29 PM Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
>
> Free all L2 (guest_mmu) roots when emulating INVEPT for L1.  Outstanding
> changes to the EPT tables managed by L1 need to be recognized, and
> relying on KVM to always flush L2's EPTP context on nested VM-Enter is
> dangerous.
>
> Similar to handle_invpcid(), rely on kvm_mmu_free_roots() to do a remote
> TLB flush if necessary, e.g. if L1 has never entered L2 then there is
> nothing to be done.
>
> Nuking all L2 roots is overkill for the single-context variant, but it's
> the safe and easy bet.  A more precise zap mechanism will be added in
> the future.  Add a TODO to call out that KVM only needs to invalidate
> affected contexts.
>
> Fixes: b119019847fbc ("kvm: nVMX: Remove unnecessary sync_roots from handle_invept")

The bug existed well before the commit indicated in the "Fixes" line.