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

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Date:   Wed, 15 Dec 2021 18:10:41 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Lai Jiangshan <laijs@...ux.alibaba.com>
Cc:     Maxim Levitsky <mlevitsk@...hat.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        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 12/15/21 17:45, Sean Christopherson wrote:
> The better place for this is the path in vmx_set_cr0() that handles EPT + !URG.
> I believe nested_vmx_restore_host_state(), which is used to restore host state if
> hardware detects a VM-Fail that KVM misses on nested VM-Enter, is also missing a
> call to mark CR3 dirty.
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 2f6f465e575f..b0c3eb80f5d5 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -4426,7 +4426,7 @@ static void nested_vmx_restore_host_state(struct kvm_vcpu *vcpu)
> 
>          nested_ept_uninit_mmu_context(vcpu);
>          vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);
> -       kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
> +       kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3);
> 
>          /*
>           * Use ept_save_pdptrs(vcpu) to load the MMU's cached PDPTRs

Yes, I agree.  Jiangshan, please send all your fixes tomorrow, or tell 
me if you prefer that I push the reverts to kvm/next.

Paolo