Re: [PATCH v4 3/3] KVM: selftests: Test behavior of KVM_X86_DISABLE_EXITS_APERFMPERF

[Mi, Dapeng]

On 6/11/2025 12:59 AM, Jim Mattson wrote:
> On Tue, Jun 10, 2025 at 1:42 AM Mi, Dapeng <dapeng1.mi@xxxxxxxxxxxxxxx> wrote:
>>
>> On 5/31/2025 2:52 AM, Jim Mattson wrote:
>>> For a VCPU thread pinned to a single LPU, verify that interleaved host
>>> and guest reads of IA32_[AM]PERF return strictly increasing values when
>>> APERFMPERF exiting is disabled.
>> Should we consider the possible overflow case of these 2 MSRs although it
>> could be extremely rare? Thanks.
> Unless someone moves the MSRs forward, at current frequencies, the
> machine will have to be up for more than 100 years. I'll be long dead
> by then.

😂


>
> Note that frequency invariant scheduling doesn't accommodate overflow
> either. If the MSRs overflow, frequency invariant scheduling is
> disabled.
Agree.