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Message-ID: <73990f49-bb72-5f73-06e4-667d92a94408@linux.alibaba.com>
Date:   Thu, 16 Dec 2021 00:43:05 +0800
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Subject: Re: [PATCH 11/15] KVM: VMX: Update vmcs.GUEST_CR3 only when the guest
 CR3 is dirty
Content-Language: en-US
From:   Lai Jiangshan <laijs@linux.alibaba.com>
To:     Maxim Levitsky <mlevitsk@redhat.com>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.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>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
References: <20211108124407.12187-1-jiangshanlai@gmail.com>
 <20211108124407.12187-12-jiangshanlai@gmail.com>
 <0271da9d3a7494d9e7439d4b8d6d9c857c83a45e.camel@redhat.com>
 <604709fa-e8bd-4eb6-6b79-8bf031a785ce@linux.alibaba.com>
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On 2021/12/16 00:31, Lai Jiangshan wrote:

> 
> What I missed is the case of "if (!enable_unrestricted_guest && !is_paging(vcpu))"
> in vmx_load_mmu_pgd() which doesn't load GUEST_CR3 but clears dirty of VCPU_EXREG_CR3
> (when after next run).

Oops.

What I missed is the case of "if (!enable_unrestricted_guest && !is_paging(vcpu))"
in vmx_load_mmu_pgd() which doesn't load GUEST_CR3 with the guest cr3 and
VCPU_EXREG_CR3 dirty bit is cleared after VMEXIT.  When !PG -> PG, GUEST_CR3 is
still the ept_identity_map_addr, and VCPU_EXREG_CR3 dirty bit is not set, so
vmx_load_mmu_pgd() doesn't update GUEST_CR3.


> So when CR0 !PG -> PG, VCPU_EXREG_CR3 dirty bit should be set.
>