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

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

> -----邮件原件-----
> 发件人: Paolo Bonzini [mailto:pbonzini@redhat.com]
> 发送时间: 2020年4月25日 0:30
> 收件人: Jim Mattson <jmattson@google.com>; Sean Christopherson
> <sean.j.christopherson@intel.com>
> 抄送: Peter Zijlstra <peterz@infradead.org>; Li,Rongqing
> <lirongqing@baidu.com>; LKML <linux-kernel@vger.kernel.org>; kvm list
> <kvm@vger.kernel.org>; the arch/x86 maintainers <x86@kernel.org>; H .
> Peter Anvin <hpa@zytor.com>; Borislav Petkov <bp@alien8.de>; Ingo Molnar
> <mingo@redhat.com>; Thomas Gleixner <tglx@linutronix.de>; Joerg Roedel
> <joro@8bytes.org>; Wanpeng Li <wanpengli@tencent.com>; Vitaly Kuznetsov
> <vkuznets@redhat.com>
> 主题: 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