linux-kernel - Re: [PATCH 2/2] KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM

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Date:   Tue, 11 Jan 2022 09:00:22 +0100
From:   Igor Mammedov <imammedo@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN

On Fri, 7 Jan 2022 19:15:43 +0100
Paolo Bonzini <pbonzini@...hat.com> wrote:

> On 1/7/22 10:02, Vitaly Kuznetsov wrote:
> > 
> > I'm again leaning towards an allowlist and currently I see only two
> > candidates:
> > 
> > CPUID.01H.EBX bits 31:24 (initial LAPIC id)
> > CPUID.0BH.EDX (x2APIC id)
> > 
> > Anything else I'm missing?  
> 
> I would also ignore completely CPUID leaves 03H, 04H, 0BH, 80000005h, 
> 80000006h, 8000001Dh, 8000001Eh (cache and processor topology), just to 
> err on the safe side.

on top of that,

1Fh

> We could change kvm_find_cpuid_entry to WARN if any of those leaves are 
> passed.
> 
> Paolo
>