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SubjectRe: [URGENT rfc patch 0/3] tsc clocksource bug fix
On Fri, Jul 05, 2013 at 11:50:05PM +0200, Thomas Gleixner wrote:
> On Fri, 5 Jul 2013, Peter Zijlstra wrote:
> > On Fri, Jul 05, 2013 at 05:24:09PM +0200, Thomas Gleixner wrote:
> > > See arch/x86/kernel/tsc.c
> > >
> > > We disable the watchdog for the TSC when tsc_clocksource_reliable is
> > > set.
> > >
> > > tsc_clocksource_reliable is set when:
> > >
> > > - you add tsc=reliable to the kernel command line
> >
> > Ah, I didn't know about that one, useful.
> >
> > > - boot_cpu_has(X86_FEATURE_TSC_RELIABLE)
> > >
> > > X86_FEATURE_TSC_RELIABLE is a software flag, set by vmware and
> > > moorsetown. So all other machines keep the watchdog enabled.
> >
> > Right.. I knew it was enabled on my machines even though they normally
> > have usable TSC.
>
> Yeah, but our well justified paranoia still prevents us from trusting
> these CPU flags. Maybe some day BIOS is going to be replaced by
> something useful. You know: Hope springs eternal....

Oh quite agreed. Its just that at several times I've wanted to disable the
thing. Now I know you can do using the kernel cmdline. Previously I had to
wreck code -- not that much harder really :-)


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