linux-kernel - Re: [RFC PATCH v2 42/69] KVM: x86/mmu: Explicitly check for MMIO spte in fast page fault

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Message-ID: <534e7bb1-6e81-f1de-3d78-022449ac5a1e@redhat.com>
Date:   Tue, 6 Jul 2021 16:54:55 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [RFC PATCH v2 42/69] KVM: x86/mmu: Explicitly check for MMIO spte
 in fast page fault

On 03/07/21 00:04, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> Explicity check for an MMIO spte in the fast page fault flow.  TDX will
> use a not-present entry for MMIO sptes, which can be mistaken for an
> access-tracked spte since both have SPTE_SPECIAL_MASK set.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/kvm/mmu/mmu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 990ee645b8a2..631b92e6e9ba 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3060,7 +3060,7 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>   			break;
>   
>   		sp = sptep_to_sp(iterator.sptep);
> -		if (!is_last_spte(spte, sp->role.level))
> +		if (!is_last_spte(spte, sp->role.level) || is_mmio_spte(spte))
>   			break;
>   
>   		/*
> 

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>