linux-kernel - Re: [PATCH 11/15] KVM: VMX: Update vmcs.GUEST

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Date:   Thu, 16 Dec 2021 00:43:05 +0800
From:   Lai Jiangshan <laijs@...ux.alibaba.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.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>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 11/15] KVM: VMX: Update vmcs.GUEST_CR3 only when the guest
 CR3 is dirty



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.
>