From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Paolo Bonzini <pbonzini@redhat.com>,
        Igor Mammedov <imammedo@redhat.com>
Cc:     kvm@vger.kernel.org, Sean Christopherson <seanjc@google.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN
In-Reply-To: <ceb63787-b057-13db-4624-b430c51625f1@redhat.com>
References: <20211122175818.608220-1-vkuznets@redhat.com>
 <20211122175818.608220-3-vkuznets@redhat.com>
 <16368a89-99ea-e52c-47b6-bd006933ec1f@redhat.com>
 <20211227183253.45a03ca2@redhat.com>
 <61325b2b-dc93-5db2-2d0a-dd0900d947f2@redhat.com>
 <87mtkdqm7m.fsf@redhat.com> <20220103104057.4dcf7948@redhat.com>
 <875yr1q8oa.fsf@redhat.com>
 <ceb63787-b057-13db-4624-b430c51625f1@redhat.com>
Date:   Wed, 05 Jan 2022 11:09:58 +0100
Message-ID: <87o84qpk7d.fsf@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 1/3/22 13:56, Vitaly Kuznetsov wrote:
>>   'allowlist' of things which can change (and put
>> *APICids there) and only fail KVM_SET_CPUID{,2} when we see something
>> else changing.
>
> We could also go the other way and only deny changes that result in 
> changed CPU caps.  That should be easier to implement since we have 
> already a mapping from CPU capability words to CPUID leaves and registers.
>

Good idea, I'll look into it (if noone beats me to it).

-- 
Vitaly