Re: [PATCH kvm-unit-tests 2/3] arm64: timer: Fix test on APM X-Gene

Christoffer Dall
2017-07-14T15:45:12Z

On Fri, Jul 14, 2017 at 09:04:10AM +0100, Marc Zyngier wrote:
> On 13/07/17 20:20, Christoffer Dall wrote:
> > When running the vtimer test on an APM X-Gene, setting the timer value
> > to (2^64 - 1) apparently results in the timer always firing, even
> > thought the counter is mich lower than the cval.
>
> Note that the system counter is only guaranteed to be at least 56 bit
> wide (see DDI0487B.a G5.1.2), and I seem to remember that X-Gene only
> has the minimum. This could explain why setting the comparator to a
> value greater than (2^56 - 1) leads to a firing timer (the comparator
> appears to be in the past).

Thanks for pointing that out, that makes good sense. So then we should
definitely fix the test.

We could either set it to 2^56 - 1 instead, or just keep the 10s as used
in this patch, because the whole test times out after 2s anyway.

Thanks,
-Christoffer