linux-kernel - Re: [RESEND RFC 0/2] Paravirtualized Control Register pinning

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Message-ID: <15b57d6b-0f46-01f5-1f75-b9b55db0611a@redhat.com>
Date:   Mon, 23 Dec 2019 18:09:30 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Liran Alon <liran.alon@...cle.com>,
        John Andersen <john.s.andersen@...el.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, sean.j.christopherson@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [RESEND RFC 0/2] Paravirtualized Control Register pinning

On 23/12/19 15:48, Liran Alon wrote:
>> Should userspace expose the CR pining CPUID feature bit, it must zero CR
>> pinned MSRs on reboot. If it does not, it runs the risk of having the
>> guest enable pinning and subsequently cause general protection faults on
>> next boot due to early boot code setting control registers to values
>> which do not contain the pinned bits.
> 
> Why reset CR pinned MSRs by userspace instead of KVM INIT handling?

Most MSRs are not reset by INIT, are they?

Paolo