Re: [PATCH v2] kvm: x86: Disable KVM_HC_CLOCK_PAIRING if tsc is in always catchup mode

Paolo Bonzini
2022-02-17T17:39:19Z

On 2/17/22 18:16, Vitaly Kuznetsov wrote:
> Paolo Bonzini <pbonzini@redhat.com> writes:
>
>> On 2/17/22 17:09, Vitaly Kuznetsov wrote:
> ...
>>> (but I still mildly dislike using 'EOPNOTSUPP' for a temporary condition
>>> on the host).
>>
>> It's not temporary, always-catchup is set on KVM_SET_TSC_KHZ and never
>> goes away.
>
> Even if the guest is migrated (back) to the host which supports TSC
> scaling?

Ah right, in that case no. But this hypercall does not have a CPUID
bit, so the supported status can change on migration anyway.

Paolo