linux-kernel - Re: [PATCH 05/54] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4

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Date:   Fri, 25 Jun 2021 12:25:46 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yu Zhang <yu.c.zhang@...ux.intel.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>
Subject: Re: [PATCH 05/54] Revert "KVM: x86/mmu: Drop
 kvm_mmu_extended_role.cr4_la57 hack"

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