linux-kernel - Re: [PATCH 09/17] KVM: x86/mmu: WARN and skip MMIO cache on private, reserved page faults

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Date: Mon, 13 May 2024 14:15:07 +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 09/17] KVM: x86/mmu: WARN and skip MMIO cache on private,
 reserved page faults

On 5/7/2024 11:58 PM, Paolo Bonzini wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> WARN and skip the emulated MMIO fastpath if a private, reserved page fault
> is encountered, as private+reserved should be an impossible combination
> (KVM should never create an MMIO SPTE for a private access).
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Message-ID: <20240228024147.41573-9-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 | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index d52794663290..0d884d0b0f35 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5819,6 +5819,9 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
>   
>   	r = RET_PF_INVALID;
>   	if (unlikely(error_code & PFERR_RSVD_MASK)) {
> +		if (WARN_ON_ONCE(error_code & PFERR_PRIVATE_ACCESS))
> +			return -EFAULT;
> +
>   		r = handle_mmio_page_fault(vcpu, cr2_or_gpa, direct);
>   		if (r == RET_PF_EMULATE)
>   			goto emulate;