Re: [PATCH 15/17] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers

Paolo Bonzini
2019-09-25T07:50:43Z

On 24/09/19 23:46, Andrea Arcangeli wrote:
>>>
>>> I would keep only EXIT_REASON_MSR_WRITE, EXIT_REASON_PREEMPTION_TIMER,
>>> EXIT_REASON_EPT_MISCONFIG and add EXIT_REASON_IO_INSTRUCTION.
>> Intuition doesn't work great when it comes to CPU speculative
>> execution runtime. I can however run additional benchmarks to verify
>> your theory that keeping around frequent retpolines will still perform
>> ok.
> On one most recent CPU model there's no measurable difference with
> your list or my list with a hrtimer workload (no cpuid). It's
> challenging to measure any difference below 0.5%.

Let's keep the short list then.

Paolo