linux-kernel - Re: [PATCH v2 3/7] KVM: nVMX: Ignore 'hv_clean_fields' data when eVMCS data is copied in vmx_get_nested

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Date:   Mon, 24 May 2021 15:56:35 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/7] KVM: nVMX: Ignore 'hv_clean_fields' data when
 eVMCS data is copied in vmx_get_nested_state()

On 17/05/21 15:50, Vitaly Kuznetsov wrote:
> 'Clean fields' data from enlightened VMCS is only valid upon vmentry: L1
> hypervisor is not obliged to keep it up-to-date while it is mangling L2's
> state, KVM_GET_NESTED_STATE request may come at a wrong moment when actual
> eVMCS changes are unsynchronized with 'hv_clean_fields'. As upon migration
> VMCS12 is used as a source of ultimate truth, we must make sure we pick all
> the changes to eVMCS and thus 'clean fields' data must be ignored.

While you're at it, would you mind making copy_vmcs12_to_enlightened and 
copy_enlightened_to_vmcs12 void?

Paolo