linux-kernel - Re: [PATCH 03/15] KVM: SVM: Inject #UD on RDTSCP when it should be disabled in the guest

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Message-ID: <1b50b090-2d6d-e13d-9532-e7195ebffe14@redhat.com>
Date:   Tue, 4 May 2021 23:57:27 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Reiji Watanabe <reijiw@...gle.com>
Subject: Re: [PATCH 03/15] KVM: SVM: Inject #UD on RDTSCP when it should be
 disabled in the guest

On 04/05/21 23:53, Sean Christopherson wrote:
>> Does the right thing happen here if the vCPU is in guest mode when
>> userspace decides to toggle the CPUID.80000001H:EDX.RDTSCP bit on or
>> off?
> I hate our terminology.  By "guest mode", do you mean running the vCPU, or do
> you specifically mean running in L2?
> 

Guest mode should mean L2.

(I wonder if we should have a capability that says "KVM_SET_CPUID2 can 
only be called prior to KVM_RUN").

Paolo