linux-kernel - Re: [PATCH] KVM: nVMX: Set X86_CR4_CET in cr4_fixed1

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Message-ID: <YD0m4cALoArLO4ek@google.com>
Date:   Mon, 1 Mar 2021 09:39:45 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     pbonzini@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: nVMX: Set X86_CR4_CET in cr4_fixed1_bits if CET IBT
 is enabled

On Thu, Feb 25, 2021, Yang Weijiang wrote:
> CET SHSTK and IBT are independently controlled by kernel, set X86_CR4_CET
> bit in cr4_fixed1_bits if either of them is enabled so that nested guest
> can enjoy the feature.
> 
> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 5856c5b81084..e92134ee081c 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7258,6 +7258,7 @@ static void nested_vmx_cr_fixed1_bits_update(struct kvm_vcpu *vcpu)
>  	cr4_fixed1_update(X86_CR4_UMIP,       ecx, feature_bit(UMIP));
>  	cr4_fixed1_update(X86_CR4_LA57,       ecx, feature_bit(LA57));
>  	cr4_fixed1_update(X86_CR4_CET,	      ecx, feature_bit(SHSTK));
> +	cr4_fixed1_update(X86_CR4_CET,	      edx, feature_bit(IBT));

Ugh, what sadist put SHSTK and IBT in separate output registers.

Reviewed-by: Sean Christopherson <seanjc@...gle.com>

>  
>  #undef cr4_fixed1_update
>  }
> -- 
> 2.26.2
>