linux-kernel - Re: [URGENT rfc patch 0/3] tsc clocksource bug fix

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.02.1307052345330.32106@ionos.tec.linutronix.de>
Date:	Fri, 5 Jul 2013 23:50:05 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Alex Shi <alex.shi@...el.com>, hpa@...ux.intel.com,
	tim.c.chen@...ux.intel.com, linux-kernel@...r.kernel.org,
	andi.kleen@...el.com, mingo@...e.hu
Subject: Re: [URGENT rfc patch 0/3] tsc clocksource bug fix

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....




--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/