Re: [PATCH 05/54] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack"

Subject: Re: [PATCH 05/54] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack"
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date: Fri, 25 Jun 2021 10:57:51 +0200
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Wanpeng Li <wanpengli@xxxxxxxxxxx>, Jim Mattson <jmattson@xxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, kvm@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Maxim Levitsky <mlevitsk@xxxxxxxxxx>
In-reply-to: <20210625084644.ort4oojvd27oy4ca@linux.intel.com>
References: <20210622175739.3610207-1-seanjc@google.com> <20210622175739.3610207-6-seanjc@google.com> <20210625084644.ort4oojvd27oy4ca@linux.intel.com>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1

On 25/06/21 10:47, Yu Zhang wrote:

But if L1 is crafty, it can load a new CR4 on VM-Exit and toggle LA57
without having to bounce through an unpaged section.  L1 can also load a


May I ask how this is done by the guest? Thanks!

It can set HOST_CR3 and HOST_CR4 to a value that is different from theone on vmentry.


Paolo

Follow-Ups:
- Re: [PATCH 05/54] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack"
  - From: Yu Zhang

References:
- [PATCH 00/54] KVM: x86/mmu: Bug fixes and summer cleaning
  - From: Sean Christopherson
- [PATCH 05/54] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack"
  - From: Sean Christopherson
- Re: [PATCH 05/54] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack"
  - From: Yu Zhang