linux-kernel - Re: [PATCH v4 4/5] KVM: MMU: Add support for PKS emulation

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Message-ID: <fd1b39b1-ce99-3626-b502-eb1324001163@redhat.com>
Date:   Thu, 29 Jul 2021 19:45:27 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Chenyi Qiang <chenyi.qiang@...el.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Xiaoyao Li <xiaoyao.li@...el.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/5] KVM: MMU: Add support for PKS emulation

On 29/07/21 19:25, Sean Christopherson wrote:
>> -		unsigned int cr4_pke:1;
>> +		unsigned int cr4_pkr:1;
> Smushing these together will not work, as this code (from below)
> 
>> -     ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
>> +     ext.cr4_pkr = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE) ||
>> +                   !!kvm_read_cr4_bits(vcpu, X86_CR4_PKS);
> will generate the same mmu_role for CR4.PKE=0,PKS=1 and CR4.PKE=1,PKS=1 (and
> other combinations).  I.e. KVM will fail to reconfigure the MMU and thus skip
> update_pkr_bitmask() if the guest toggles PKE or PKS while the other PK* bit is set.
> 

I'm also not sure why there would be issues in just using cr4_pks.

Paolo