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Date: Fri, 16 Dec 2016 12:53:24 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Ingo Molnar <mingo@kernel.org>
cc: LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>,
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        Kevin Stanton <kevin.b.stanton@intel.com>,
        Allen Hung <allen_hung@dell.com>, stable@vger.kernel.org
Subject: Re: [patch 2/2] x86/tsc: Force TSC_ADJUST register to value >=
 zero
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On Fri, 16 Dec 2016, Ingo Molnar wrote:
> * Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > We have two options:
> > 
> > 1) Disable TSC deadline timer by default and force users with sane machines
> >    to enable it on the kernel command line.
> > 
> >    Upside:   Very small patch
> >    
> >    Downside: Degrades existing setups on sane machines, keeps TSC unusable
> >       	     on affected machines. We have no idea what other hidden side
> >       	     effects the TSC_ADJUST tinkering has. If there are any, they
> >       	     ain't be nice ones.
> > 
> > 2) Push the whole TSC_ADJUST sanitizing machinery into stable
> > 
> >    Upside:   Does not affect sane machines and gives a benefit to users of
> >    	     affected machines
> > 
> >    Downside: Rather large patch, but not that risky either. Needs a few
> > 	     eyes and good test coverage though
> > 
> > Thoughts?
> 
> I'd go for #2, because #1 is essentially turning it off for almost everyone.
> 
> We can still do #1 and push it back to -stable as well if #2 fails.
> 
> But I'd suggest we delay the stable backporting until it's been upstream a bit.

I agree. None of these patches is tagged stable. I just wanted to mention
it so it can be discussed before distros/stable users are swamped with
failure reports.

Thanks,

	tglx