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

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Date:   Tue, 3 Aug 2021 16:52:52 +0800
From:   Chenyi Qiang <chenyi.qiang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.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>,
        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 7/30/2021 1:45 AM, Paolo Bonzini wrote:
> 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.
> 

Will split out the pke and pks.

Thanks
Chenyi

> Paolo
>