Re: [Qemu-devel] [PATCH 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

[Paolo Bonzini]

On 16/03/2018 16:05, Vitaly Kuznetsov wrote:
>>>  
>>> -        if (has_msr_hv_frequencies && tsc_is_stable_and_known(env)) {
>>> +        if (has_msr_hv_frequencies && env->tsc_khz) {
>> Should this be
>>
>> ((env->tsc_khz && has_msr_hv_reenlightenment) ||
>>  tsc_is_stable_and_known(env))
>>
>> so that you don't regress on older kernels?
>>
> I don't actually see where the regression might come from: frequency
> MSRs are supported regardless or reenlightenment/invtsc and there's
> nothing wrong with exposing them but I may be missing something..

On older kernel without re-enlightenment support, you don't want to
expose the frequency MSRs unless invtsc is on, right?

Paolo