linux-kernel - Re: [PATCH 02/23] KVM: MMU: nested EPT cannot be used in SMM

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Date:   Fri, 4 Feb 2022 18:16:03 +0000
From:   David Matlack <dmatlack@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        seanjc@...gle.com, vkuznets@...hat.com
Subject: Re: [PATCH 02/23] KVM: MMU: nested EPT cannot be used in SMM

On Fri, Feb 04, 2022 at 06:56:57AM -0500, Paolo Bonzini wrote:
> The role.base.smm flag is always zero, do not bother copying it over
> from vcpu->arch.root_mmu.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Reviewed-by: David Matlack <dmatlack@...gle.com>

> ---
>  arch/x86/kvm/mmu/mmu.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 9424ae90f1ef..b0065ae3cea8 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4881,9 +4881,6 @@ kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
>  {
>  	union kvm_mmu_role role = {0};
>  
> -	/* SMM flag is inherited from root_mmu */
> -	role.base.smm = vcpu->arch.root_mmu.mmu_role.base.smm;

nit: Retaining a comment here and/or warning here would be useful.

	/* EPT is not allowed in SMM */
	WARN_ONCE_ONCE(vcpu->arch.root_mmu.mmu_role.base.smm);

(Although I imagine it would just get removed later in the series.)

> -
>  	role.base.level = level;
>  	role.base.has_4_byte_gpte = false;
>  	role.base.direct = false;
> -- 
> 2.31.1
> 
>