Re: The SMP RHEL 5.1 PAE guest can't boot up issue

Zhao Forrest
2008-02-29T08:26:30Z

>
> I believe the patch is still necessary, since we still need to guarantee
> that a vcpu's tsc is monotonous. I think there are three issues to be
> addressed:
>
> 1. The majority of intel machines don't need the offset adjustment since
> they already have a constant rate tsc that is synchronized on all cpus.
> I think this is indicated by X86_FEATURE_CONSTANT_TSC (though I'm not
> 100% certain if it means that the rate is the same for all cpus, Thomas
> can you clarify?)
>
> This will improve tsc quality for those machines, but we can't depend on
> it, since some machines don't have constant tsc. Further, I don't think
> really large machines can have constant tsc since clock distribution
> becomes difficult or impossible.
>
I have another newbie question: can the current Linux kernel handle the unsynced
TSC? If kernel can't handle this case, it still has problem to run
Linux on hardware
with unsynced TSC.

Thanks,
Forrest