linux-kernel - Re: [PATCH] raise tsc clocksource rating

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 for Android: free password hash cracker in your pocket

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

Date:	Mon, 29 Oct 2007 23:55:28 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Zachary Amsden <zach@...are.com>,
	Glauber de Oliveira Costa <gcosta@...hat.com>,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	rusty@...tcorp.com.au, --cc@...hat.com, avi@...amnet.com,
	kvm-devel@...ts.sourceforge.net,
	Glauber de Oliveira Costa <glauber@....localdomain>,
	Dan Hecht <dhecht@...are.com>,
	Garrett Smith <garrett@...are.com>
Subject: Re: [PATCH] raise tsc clocksource rating


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> > if it's inaccurate why are you exposing it to the guest then? Native 
> > only uses the TSC if it's safe and accurate to do so.
> 
> It is used as part of the Xen clocksource as a short term 
> extrapolator, with correction parameters supplied by the hypervisor.  
> It should never be used directly.

that's totally broken then. You cannot create an SMP-safe monotonic 
clocksource via interpolation - native does not do it either. Good thing 
this problem got exposed, it needs to be fixed.

	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/