# Re: \[PATCH v2 4/5\] KVM: selftests: Add a test for KVM\_RUN+rseq to detect task migration bugs

- From: Mathieu Desnoyers \<mathieu.desnoyers@efficios.com\>
- Date: 2021-08-28 00:06:36 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2021/08/1490978
- Thread: https://ratatoskr.run/linux-arm-kernel/2021/08/1484561/t.md

```text
----- On Aug 27, 2021, at 7:23 PM, Sean Christopherson seanjc@google.com wrote:

> On Fri, Aug 27, 2021, Mathieu Desnoyers wrote:
[...]
>> Does it reproduce if we randomize the delay to have it picked randomly from 0us
>> to 100us (with 1us step) ? It would remove a lot of the needs for arch-specific
>> magic delay value.
> 
> My less-than-scientific testing shows that it can reproduce at delays up to
> ~500us,
> but above ~10us the reproducibility starts to drop.  The bug still reproduces
> reliably, it just takes more iterations, and obviously the test runs a bit
> slower.
> 
> Any objection to using a 1-10us delay, e.g. a simple usleep((i % 10) + 1)?

Works for me, thanks!

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

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