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

[Paolo Bonzini]

On 29/04/20 10:54, Peter Zijlstra wrote:
> On Wed, Apr 29, 2020 at 01:46:36PM +0800, 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
> Would it make sense to provide a pass-through APERF/MPERF for
> KVM_HINTS_REALTIME ? Because that hint guarantees we have a 1:1 vCPU:CPU
> binding and guaranteed no over-commit.
> 

Yes but that's up to userspace.

Paolo