linux-kernel - Re: [PATCH v2 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT

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Date:   Wed, 29 May 2019 09:38:13 +0800
From:   Tao Xu <tao3.xu@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, rkrcmar@...hat.com,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        hpa@...or.com, sean.j.christopherson@...el.com
Cc:     x86@...nel.org, kvm@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, jingqi.liu@...el.com
Subject: Re: [PATCH v2 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL

On 29/05/2019 09:29, Paolo Bonzini wrote:
> On 24/05/19 09:56, Tao Xu wrote:
>> +
>> +	if (rdmsrl_safe(MSR_IA32_UMWAIT_CONTROL, &host_umwait_control))
>> +		return;
>> +
> 
> Does the host value ever change?  If not, this can perhaps be read once
> when kvm_intel is loaded.  And if it changes often, it should be
> shadowed into a percpu variable.
> 
> Paolo
> 

Yes, the host value may change, we contact the host patch author Fenghua 
to add the shadow in host when the host msr value change. And we will 
improve this in the next version of patch.