From: Andi Kleen <andi@firstfloor.org>
To: John <linux.kernel@free.fr>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Disabling x86 System Management Mode
Date: 17 Apr 2007 00:12:21 +0200 [thread overview]
Message-ID: <p73odlo55q2.fsf@bingen.suse.de> (raw)
In-Reply-To: <46235447.3080000@free.fr>
John <linux.kernel@free.fr> writes:
Please use a full real name for posting.
> AFAIU, even a hard real-time OS is "defenseless" against SMIs that
> kick the CPU into SMM.
There are usually chipset specific bits that can be set to disable SMMs.
See the datasheet if you can get them. Unfortunately most chipset vendors
don't give out data sheets easily.
> .globl foo
> foo:
> push %ebx
> push %esi
> cpuid
> rdtsc
At least some SMM implementations restore the old TSC value. Sad but true.
Besides RDTSC can be speculated around on some CPUs which also adds errors.
-Andi
next prev parent reply other threads:[~2007-04-16 21:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-16 10:47 Disabling x86 System Management Mode John
2007-04-16 11:31 ` John
2007-04-16 15:12 ` Lee Revell
2007-04-16 22:12 ` Andi Kleen [this message]
2007-04-17 16:49 ` John Sigler
2007-04-17 16:57 ` Andi Kleen
2007-04-17 21:32 ` John Sigler
2007-04-17 17:01 ` John Sigler
2007-04-18 8:09 ` John Sigler
2007-04-18 11:41 ` John Sigler
2007-04-18 14:06 ` Andrew Shewmaker
2007-04-18 14:39 ` John Sigler
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