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From: "Jan Beulich" <jbeulich@novell.com>
To: "Ingo Molnar" <mingo@elte.hu>, "Roland McGrath" <roland@redhat.com>
Cc: "Thomas Gleixner" <tglx@linutronix.de>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: prevent unconditional writes to DebugCtl MSR
Date: Mon, 21 Apr 2008 17:34:19 +0100	[thread overview]
Message-ID: <480CDE2B.76E4.0078.0@novell.com> (raw)
In-Reply-To: <20080421155534.GA1284@elte.hu>

>>> Ingo Molnar <mingo@elte.hu> 21.04.08 17:55 >>>
>
>* Roland McGrath <roland@redhat.com> wrote:
>
>> If TIF_DEBUGCTLMSR is ever set on a machine without the support, that 
>> is a bug we should diagnose earlier.  If you want some paranoia, then 
>> keep update_debugctlmsr but make it do:
>> 
>> 	BUG_ON(boot_cpu_data.x86 < 6);
>> 
>> instead.
>
>agreed. Jan, wanna send a fix for this?

Hmm, without knowing the context here I'd say the way it's done in
.25 is quite reasonable; a BUG_ON() here would seem quite rude to
me. I thought it really should be the call sites ensuring this doesn't
get called, and the silent ignoring is just to prevent bringing the
system down. A WARN_ON() (or perhaps even WARN_ON_ONCE()) would
be the most I'd be inclined to add there.

Jan


  reply	other threads:[~2008-04-21 16:34 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-18 19:43 Roland McGrath
2008-04-21 15:55 ` Ingo Molnar
2008-04-21 16:34   ` Jan Beulich [this message]
2008-04-21 21:30     ` Roland McGrath
  -- strict thread matches above, loose matches on Subject: below --
2008-03-10 13:11 Jan Beulich
2008-03-10 15:56 ` Andi Kleen
2008-03-10 17:14 ` Ingo Molnar

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