çå: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers

[Li,Rongqing]

> -----éäåä-----
> åää: Paolo Bonzini [mailto:pbonzini@xxxxxxxxxx]
> åéæé: 2020å4æ25æ 0:30
> æää: Jim Mattson <jmattson@xxxxxxxxxx>; Sean Christopherson
> <sean.j.christopherson@xxxxxxxxx>
> æé: Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Li,Rongqing
> <lirongqing@xxxxxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>; kvm list
> <kvm@xxxxxxxxxxxxxxx>; the arch/x86 maintainers <x86@xxxxxxxxxx>; H .
> Peter Anvin <hpa@xxxxxxxxx>; Borislav Petkov <bp@xxxxxxxxx>; Ingo Molnar
> <mingo@xxxxxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Joerg Roedel
> <joro@xxxxxxxxxx>; Wanpeng Li <wanpengli@xxxxxxxxxxx>; Vitaly Kuznetsov
> <vkuznets@xxxxxxxxxx>
> äé: Re: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers
> 
> On 24/04/20 18:25, Jim Mattson wrote:
> >> Assuming we're going forward with this, at an absolute minimum the
> >> RDMSRs need to be wrapped with checks on host _and_ guest support for
> >> the emulated behavior.  Given the significant overhead, this might
> >> even be something that should require an extra opt-in from userspace to
> enable.
> >
> > I would like to see performance data before enabling this unconditionally.
> 
> I wouldn't want this to be enabled unconditionally anyway, because you need to
> take into account live migration to and from processors that do not have
> APERF/MPERF support.
> 
> Paolo

I will add a kvm parameter to consider whether enable MPERF/APERF emulations, and make default value to false

Thanks

-Li