linux-kernel - Re: [patch 1/2] x86/tsc: Validate TSC

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Date:   Tue, 13 Dec 2016 14:23:36 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>,
        Bruce Schlobohm <bruce.schlobohm@...el.com>,
        Roland Scheidegger <rscheidegger_lists@...peed.ch>,
        Kevin Stanton <kevin.b.stanton@...el.com>,
        Allen Hung <allen_hung@...l.com>
Subject: Re: [patch 1/2] x86/tsc: Validate TSC_ADJUST after resume

On Tue, 13 Dec 2016, Peter Zijlstra wrote:

> On Tue, Dec 13, 2016 at 01:14:17PM -0000, Thomas Gleixner wrote:
> > --- a/arch/x86/power/cpu.c
> > +++ b/arch/x86/power/cpu.c
> > @@ -256,6 +256,7 @@ static void notrace __restore_processor_
> >  	mtrr_bp_restore();
> >  	perf_restore_debug_store();
> >  	msr_restore_context(ctxt);
> > +	tsc_verify_tsc_adjust(true);
> >  }
> 
> Should we do that sooner, as in before calling
> restore_sched_clock_state() ? Otherwise we recompute the sched_clock
> deltas vs the wrecked TSC and then fix it up through the ADJUST,
> wrecking our sched clock again.

Ah. Indeed. Will fix. That needs some thought on the secondary CPUs as
well...

Thanks,

	tglx