linux-kernel - Re: [PATCH v16 32/51] KVM: nVMX: Add consistency checks for CR0.WP and CR4.CET

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Message-ID: <f06fe1c9-7042-4373-93b1-6a51acc4316b@linux.intel.com>
Date: Mon, 22 Sep 2025 16:47:21 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, Tom Lendacky <thomas.lendacky@....com>,
 Mathias Krause <minipli@...ecurity.net>, John Allen <john.allen@....com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>, Chao Gao <chao.gao@...el.com>,
 Xiaoyao Li <xiaoyao.li@...el.com>, Maxim Levitsky <mlevitsk@...hat.com>,
 Zhang Yi Z <yi.z.zhang@...ux.intel.com>, Xin Li <xin@...or.com>
Subject: Re: [PATCH v16 32/51] KVM: nVMX: Add consistency checks for CR0.WP
 and CR4.CET



On 9/20/2025 6:32 AM, Sean Christopherson wrote:
> From: Chao Gao <chao.gao@...el.com>
>
> Add consistency checks for CR4.CET and CR0.WP in guest-state or host-state
> area in the VMCS12. This ensures that configurations with CR4.CET set and
> CR0.WP not set result in VM-entry failure, aligning with architectural
> behavior.
>
> Tested-by: Mathias Krause <minipli@...ecurity.net>
> Tested-by: John Allen <john.allen@....com>
> Tested-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> Signed-off-by: Chao Gao <chao.gao@...el.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>

> ---
>   arch/x86/kvm/vmx/nested.c | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 11e5d3569933..51c50ce9e011 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -3110,6 +3110,9 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
>   	    CC(!kvm_vcpu_is_legal_cr3(vcpu, vmcs12->host_cr3)))
>   		return -EINVAL;
>   
> +	if (CC(vmcs12->host_cr4 & X86_CR4_CET && !(vmcs12->host_cr0 & X86_CR0_WP)))
> +		return -EINVAL;
> +
>   	if (CC(is_noncanonical_msr_address(vmcs12->host_ia32_sysenter_esp, vcpu)) ||
>   	    CC(is_noncanonical_msr_address(vmcs12->host_ia32_sysenter_eip, vcpu)))
>   		return -EINVAL;
> @@ -3224,6 +3227,9 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
>   	    CC(!nested_guest_cr4_valid(vcpu, vmcs12->guest_cr4)))
>   		return -EINVAL;
>   
> +	if (CC(vmcs12->guest_cr4 & X86_CR4_CET && !(vmcs12->guest_cr0 & X86_CR0_WP)))
> +		return -EINVAL;
> +
>   	if ((vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS) &&
>   	    (CC(!kvm_dr7_valid(vmcs12->guest_dr7)) ||
>   	     CC(!vmx_is_valid_debugctl(vcpu, vmcs12->guest_ia32_debugctl, false))))