linux-kernel - Re: [PATCH 1/1] KVM: x86: fix MSR_IA32

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Message-ID: <6310fbe66e89b9f82ac88f7f080ea2eff2dad74e.camel@redhat.com>
Date:   Mon, 21 Sep 2020 12:26:52 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH 1/1] KVM: x86: fix MSR_IA32_TSC read for nested migration

On Thu, 2020-09-17 at 09:14 -0700, Sean Christopherson wrote:
> On Thu, Sep 17, 2020 at 02:07:23PM +0300, Maxim Levitsky wrote:
> > +		 * Intel PRM states that MSR_IA32_TSC read adds the TSC offset
> 
> One more nit, "Intel SDM" would be preferred as that's most commonly used in
> KVM changelogs, and there are multiple PRM acronyms in Intel's dictionary
> these days.
Fixed.

Best regards,
	Maxim Levitsky

> 
> > +		 * even when not intercepted. AMD manual doesn't define this
> > +		 * but appears to behave the same
> > +		 *
> > +		 * However when userspace wants to read this MSR, return its
> > +		 * real L1 value so that its restore will be correct
> > +		 *
> > +		 */
> > +		if (msr_info->host_initiated)
> > +			msr_info->data = kvm_read_l1_tsc(vcpu, rdtsc());
> > +		else
> > +			msr_info->data = kvm_read_l2_tsc(vcpu, rdtsc());
> >  		break;
> >  	case MSR_MTRRcap:
> >  	case 0x200 ... 0x2ff:
> > -- 
> > 2.26.2
> >