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Subject: Re: [PATCH 05/54] Revert "KVM: x86/mmu: Drop
 kvm_mmu_extended_role.cr4_la57 hack"
To:     Yu Zhang <yu.c.zhang@linux.intel.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Maxim Levitsky <mlevitsk@redhat.com>
References: <20210622175739.3610207-1-seanjc@google.com>
 <20210622175739.3610207-6-seanjc@google.com>
 <20210625084644.ort4oojvd27oy4ca@linux.intel.com>
 <09a49caf-6ff5-295b-d1ab-023549f6a23b@redhat.com>
 <20210625092902.o4kqx67zvvbudggh@linux.intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <885018ab-206b-35c7-a75a-e4fccb663fc3@redhat.com>
Date:   Fri, 25 Jun 2021 12:25:46 +0200
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On 25/06/21 11:29, Yu Zhang wrote:
> Thanks, Paolo.
> 
> Do you mean the L1 can modify its paging mode by setting HOST_CR3 as root of
> a PML5 table in VMCS12 and HOST_CR4 with LA57 flipped in VMCS12, causing the
> GUEST_CR3/4 being changed in VMCS01, and eventually updating the CR3/4 when
> L0 is injecting a VM Exit from L2?

Yes, you can even do that without a "full" vmentry by setting invalid 
guest state in vmcs12. :)

Paolo