linux-kernel - Re: [PATCH v3 04/12] KVM: X86: Add a ratio parameter to kvm_scale

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Message-ID: <f266a026b803f1f130cedf06d12e784956888156.camel@redhat.com>
Date:   Mon, 24 May 2021 20:50:41 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Ilias Stamatis <ilstam@...zon.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     seanjc@...gle.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, zamsden@...il.com,
        mtosatti@...hat.com, dwmw@...zon.co.uk
Subject: Re: [PATCH v3 04/12] KVM: X86: Add a ratio parameter to
 kvm_scale_tsc()

On Mon, 2021-05-24 at 16:23 +0200, Paolo Bonzini wrote:
> On 21/05/21 12:24, Ilias Stamatis wrote:
> > @@ -3537,10 +3539,14 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >   		 * return L1's TSC value to ensure backwards-compatible
> >   		 * behavior for migration.
> >   		 */
> > -		u64 tsc_offset = msr_info->host_initiated ? vcpu->arch.l1_tsc_offset :
> > -							    vcpu->arch.tsc_offset;
> > -
> > -		msr_info->data = kvm_scale_tsc(vcpu, rdtsc()) + tsc_offset;
> > +		if (msr_info->host_initiated)
> > +			msr_info->data = kvm_scale_tsc(
> > +				vcpu, rdtsc(), vcpu->arch.l1_tsc_scaling_ratio
> > +				) + vcpu->arch.l1_tsc_offset;
> 
> Better indentation:
> 
> 	msr_info->data = vcpu->arch.l1_tsc_offset +
> 		kvm_scale_tsc(vcpu, rdtsc(),
> 			      vcpu->arch.tsc_scaling_ratio);

Good idea IMHO.
Other than that:

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>



> 
> Same below.
> 
> Paolo
> 
> > +		else
> > +			msr_info->data = kvm_scale_tsc(
> > +				vcpu, rdtsc(), vcpu->arch.tsc_scaling_ratio
> > +				) + vcpu->arch.tsc_offset;
> >   		break;
> >   	}
> >   	case MSR_MTRRcap:
> >