From owner-freebsd-security@FreeBSD.ORG Sat May 14 07:15:00 2005 Return-Path: Delivered-To: freebsd-security@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8340116A4CE for ; Sat, 14 May 2005 07:15:00 +0000 (GMT) Received: from pd3mo1so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net [24.71.223.10]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4009743D7E for ; Sat, 14 May 2005 07:15:00 +0000 (GMT) (envelope-from cperciva@freebsd.org) Received: from pd3mr6so.prod.shaw.ca (pd3mr6so-qfe3.prod.shaw.ca [10.0.141.21])2004))freebsd-security@freebsd.org; Sat, 14 May 2005 01:14:52 -0600 (MDT) Received: from pn2ml6so.prod.shaw.ca ([10.0.121.150]) by pd3mr6so.prod.shaw.ca (Sun ONE Messaging Server 6.0 HotFix 1.01 (built Mar 15 2004)) with ESMTP id <0IGG00I1YXGS0RG0@pd3mr6so.prod.shaw.ca> for freebsd-security@freebsd.org; Sat, 14 May 2005 01:14:52 -0600 (MDT) Received: from [127.0.0.1] (S0106006067227a4a.vc.shawcable.net [24.87.209.6]) 2003))freebsd-security@freebsd.org; Sat, 14 May 2005 01:14:52 -0600 (MDT) Date: Sat, 14 May 2005 03:14:50 -0400 From: Colin Percival In-reply-to: <3aaaa3a050514000629cc8427@mail.gmail.com> To: Chris Message-id: <4285A56A.1030106@freebsd.org> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1 Content-transfer-encoding: 7bit X-Accept-Language: en-us, en X-Enigmail-Version: 0.91.0.0 References: <245f0df105051318564b1ffb6b@mail.gmail.com> <94145.1116037219@critter.freebsd.dk> <245f0df105051322354e8e86eb@mail.gmail.com> <3aaaa3a050514000629cc8427@mail.gmail.com> User-Agent: Mozilla Thunderbird 1.0.2 (X11/20050406) cc: freebsd-security@freebsd.org cc: Poul-Henning Kamp cc: "Drew B. \[Security Expertise/Freelance Security research\]." Subject: Re: FreeBSD Security Advisory FreeBSD-SA-05:09.htt [REVISED] X-BeenThere: freebsd-security@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Security issues [members-only posting] List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 May 2005 07:15:00 -0000 Chris wrote: > I am somewhat confused by applying the patch, does this disable HTT > functionality? or does a patched server close the issue and keep HTT > enabled? The patch adds a new loader tunable, machdep.hyperthreading_allowed, which is set to 0 by default. Regardless of how you try to set the machdep.hlt_cpus_mask and machdep.hlt_logical_cpus sysctls, if machdep.hyperthreading_allowed is set to zero then you will not have any process threads executing on the second hyper-thread from each core. If you're on a system where this isn't a problem (e.g., anything with no local users), you can set machdep.hyperthreading_allowed=1 in /boot/loader.conf or via the sysctl after booting, and get the benefit of hyperthreading. Colin Percival