RE: [Xen-devel] [RFC] [PATCH] use "reliable" tsc properly when available, but verify

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> > I'd feel better running check_tsc_warp (at least) once
> > on ALL processors, even if X86_FEATURE_TSC_RELIABLE
> > is set.  Is that OK?  Or should we just trust it under
> > exactly the same circumstances as Linux does?
> 
> Well, what does trusting it imply for us right now? Do you 
> have another
> patch in mind, even if we decide against check_tsc_warp?
> 
> I mean, I'm not unhappy with our TSC management code as it is. I'm not
> greatly excited to mess with it yet again.

Well, if it is indeed reliable, there's no reason that
Xen should write_tsc, though it might be interesting
to check_tsc_warp on various hardware before and after
Xen does write_tsc (to see if Xen is breaking anything).

But I could certainly code the patch to just "measure
and report" for now and we could revisit Xen's use of
write_tsc at a later time if that's your preference.

I definitely have more patches in mind for pvrdtsc but
may not get back to them for a few weeks, so was
hoping to validate tsc reliability on some machines
in the meantime.

Thanks,
Dan

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