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From: Ingo Molnar <mingo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Borislav Petkov <bp@alien8.de>,
	Bruce Schlobohm <bruce.schlobohm@intel.com>,
	Roland Scheidegger <rscheidegger_lists@hispeed.ch>,
	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
Date: Fri, 16 Dec 2016 12:52:54 +0100	[thread overview]
Message-ID: <20161216115254.GA18902@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1612161121140.3470@nanos>


* 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.

Thanks,

	Ingo

  reply	other threads:[~2016-12-16 12:00 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-13 13:14 [patch 0/2] tsc/adjust: Cure suspend/resume issues and prevent TSC deadline timer irq storm Thomas Gleixner
2016-12-13 13:14 ` [patch 2/2] x86/tsc: Force TSC_ADJUST register to value >= zero Thomas Gleixner
2016-12-13 13:43   ` Peter Zijlstra
2016-12-13 15:49     ` Thomas Gleixner
2016-12-15 10:53   ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2016-12-16 11:46   ` [patch 2/2] " Thomas Gleixner
2016-12-16 11:52     ` Ingo Molnar [this message]
2016-12-16 11:53       ` Thomas Gleixner
2016-12-16 13:33     ` Thomas Gleixner
2016-12-13 13:14 ` [patch 1/2] x86/tsc: Validate TSC_ADJUST after resume Thomas Gleixner
2016-12-13 13:22   ` Peter Zijlstra
2016-12-13 13:23     ` Thomas Gleixner
2016-12-15 10:52   ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2016-12-13 16:34 ` [patch 0/2] tsc/adjust: Cure suspend/resume issues and prevent TSC deadline timer irq storm Roland Scheidegger
2016-12-13 16:46   ` Thomas Gleixner
2016-12-14  1:36     ` Roland Scheidegger
2016-12-14  7:31       ` Thomas Gleixner
2016-12-14 20:59         ` Thomas Gleixner
2016-12-14 21:40           ` Thomas Gleixner
2016-12-14 22:54             ` Roland Scheidegger
2016-12-15  9:31               ` Thomas Gleixner
2017-01-26 23:40                 ` Stanton, Kevin B

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