linux-kernel - Re: [PATCH 12/17] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO

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Date: Mon, 13 May 2024 14:26:11 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH 12/17] KVM: x86/mmu: Explicitly disallow private accesses
 to emulated MMIO

On 5/7/2024 11:58 PM, Paolo Bonzini wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> Explicitly detect and disallow private accesses to emulated MMIO in
> kvm_handle_noslot_fault() instead of relying on kvm_faultin_pfn_private()
> to perform the check.  This will allow the page fault path to go straight
> to kvm_handle_noslot_fault() without bouncing through __kvm_faultin_pfn().
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Message-ID: <20240228024147.41573-12-seanjc@...gle.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>

> ---
>   arch/x86/kvm/mmu/mmu.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index a8e14c2b68a7..fdae6d19e72b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3262,6 +3262,11 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
>   {
>   	gva_t gva = fault->is_tdp ? 0 : fault->addr;
>   
> +	if (fault->is_private) {
> +		kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
> +		return -EFAULT;
> +	}
> +
>   	vcpu_cache_mmio_info(vcpu, gva, fault->gfn,
>   			     access & shadow_mmio_access_mask);
>