linux-kernel - Re: [PATCH] KVM: x86/mmu: Do not create SPTEs for GFNs that exceed host.MAXPHYADDR

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Message-ID: <8e2213fa-981a-11cd-5bcc-3338d3b2c5de@redhat.com>
Date:   Mon, 2 May 2022 13:52:10 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Kai Huang <kai.huang@...el.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>,
        Ben Gardon <bgardon@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH] KVM: x86/mmu: Do not create SPTEs for GFNs that exceed
 host.MAXPHYADDR

On 5/2/22 13:12, Kai Huang wrote:
>> -		if (unlikely(!enable_mmio_caching)) {
>> +		if (unlikely(!enable_mmio_caching) ||
>> +		    unlikely(fault->gfn > kvm_mmu_max_gfn_host())) {
> Shouldn't we check fault->gfn against cpuid_maxphyaddr(vcpu) instead of
> kvm_mmu_max_gfn_host() here?

No, the point of this check is to handle the case where 
kvm_mmu_max_gfn_host() is smaller than cpuid_maxphyaddr().

Paolo