linux-kernel - Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer

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]

Date:	Sat, 17 Mar 2007 08:22:27 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Adrian Bunk <bunk@...sta.de>,
	Arjan van de Ven <arjan@...radead.org>,
	Len Brown <lenb@...nel.org>
Subject: Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer


* Thomas Gleixner <tglx@...utronix.de> wrote:

> When PM-Timer is available for local APIC timer calibration we can 
> skip the verification of the calibrated time value. The resulting 
> error is quite small on a bunch of evaluated platforms and is less 
> harming than the observed false positives.
> 
> We need to keep the verification on systems, which have no PM-Timer to 
> avoid bogus local APIC timer calibrations in the range of factor 2-10, 
> which can be observed when swicthing off the PM-timer support in the 
> kernel configuration.
> 
> The wrong calibration values are probably caused by SMM code trying to 
> emulate a PS/2 keyboard from a (maybe connected or not) USB keyboard. 
> This prohibits the accurate delivery of PIT interrupts, which are used 
> to calibrate the local APIC timer. Unfortunately we have no way to 
> disable this BIOS misfeature in the early boot process.
> 
> Add also the dropped cpu_relax() back to the wait loops.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Acked-by: Ingo Molnar <mingo@...e.hu>

	Ingo
-
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/