Re: [PATCH v10 1/7] x86/tsc: remove tsc_disabled flag

[Thomas Gleixner]

On Tue, 19 Jun 2018, Peter Zijlstra wrote:
> On Tue, Jun 19, 2018 at 07:32:49PM +0200, Thomas Gleixner wrote:
> > On Fri, 15 Jun 2018, Pavel Tatashin wrote:
> > 
> > > tsc_disabled is set when notsc is passed as kernel parameter. The reason we
> > > have notsc is to avoid timing problems on multi-socket systems.  We already
> > > have a mechanism, however, to detect and resolve these issues by invoking
> > > tsc unstable path. Thus, make notsc to behave the same as tsc=unstable.
> > 
> > notsc also excludes TSC from being used at all
> 
> It does not; there is TSC usage even if you boot with notsc on. See how
> it does not clear X86_FEATURE_TSC for instance.

Well, kinda. There is some stuff in the apic calibration which uses TSC
independent of tsc_disabled, but that's about it.

Thanks,

	tglx