答复: [PATCH][v2] kvm: x86: emulate APERF/MPERF registers

["Li,Rongqing" <lirongqing@baidu.com>]

> -----邮件原件-----
> 发件人: Xiaoyao Li [mailto:xiaoyao.li@intel.com]
> 发送时间: 2020年4月30日 14:49
> 收件人: Li,Rongqing <lirongqing@baidu.com>; linux-kernel@vger.kernel.org;
> kvm@vger.kernel.org; x86@kernel.org; hpa@zytor.com; bp@alien8.de;
> mingo@redhat.com; tglx@linutronix.de; joro@8bytes.org;
> jmattson@google.com; wanpengli@tencent.com; vkuznets@redhat.com;
> sean.j.christopherson@intel.com; pbonzini@redhat.com
> 主题: Re: [PATCH][v2] kvm: x86: emulate APERF/MPERF registers
> 
> On 4/29/2020 1:46 PM, Li RongQing wrote:
> > Guest kernel reports a fixed cpu frequency in /proc/cpuinfo, this is
> > confused to user when turbo is enable, and aperf/mperf can be used to
> > show current cpu frequency after 7d5905dc14a
> > "(x86 / CPU: Always show current CPU frequency in /proc/cpuinfo)"
> > so we should emulate aperf mperf to achieve it
> >
> > the period of aperf/mperf in guest mode are accumulated as emulated
> > value, and add per-VM knod to enable emulate mperfaperf
> >
> > diff v1:
> > 1. support AMD
> > 2. support per-vm capability to enable
> >
> [...]
> > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index
> > 851e9cc79930..1d157a8dba46 100644
> > --- a/arch/x86/kvm/svm.c
> > +++ b/arch/x86/kvm/svm.c
> > @@ -4310,6 +4310,12 @@ static int svm_get_msr(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
> >   	case MSR_F10H_DECFG:
> >   		msr_info->data = svm->msr_decfg;
> >   		break;
> > +	case MSR_IA32_MPERF:
> > +		msr_info->data = vcpu->arch.v_mperf;
> > +		break;
> > +	case MSR_IA32_APERF:
> > +		msr_info->data = vcpu->arch.v_aperf;
> > +		break;
> >   	default:
> >   		return kvm_get_msr_common(vcpu, msr_info);
> >   	}
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index
> > 91749f1254e8..b05e276e262b 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -1914,6 +1914,12 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
> >   		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> >   			return 1;
> >   		goto find_shared_msr;
> > +	case MSR_IA32_MPERF:
> > +		msr_info->data = vcpu->arch.v_mperf;
> > +		break;
> > +	case MSR_IA32_APERF:
> > +		msr_info->data = vcpu->arch.v_aperf;
> > +		break;
> 
> They are same for both vmx and svm, you can put them in
> kvm_get_msr_common()
> 

Ok

> BTW, are those two MSR always readable regardless of guest's CPUID?

It should be, not sure if there is abnormal

thanks
-LiRongQing

> >   	default:
> >   	find_shared_msr:
> >   		msr = find_msr_entry(vmx, msr_info->index);
>