From owner-cvs-src@FreeBSD.ORG Mon May 16 08:00:41 2005 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 53D6416A4CE; Mon, 16 May 2005 08:00:41 +0000 (GMT) Received: from mail25.syd.optusnet.com.au (mail25.syd.optusnet.com.au [211.29.133.166]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7F1A443DA7; Mon, 16 May 2005 08:00:40 +0000 (GMT) (envelope-from peterjeremy@optushome.com.au) Received: from server.vk2pj.dyndns.org (c211-30-75-229.belrs2.nsw.optusnet.com.au [211.30.75.229]) j4G80Z3P017983 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO); Mon, 16 May 2005 18:00:35 +1000 Received: from server.vk2pj.dyndns.org (localhost.vk2pj.dyndns.org [127.0.0.1])j4G80Zjm021454; Mon, 16 May 2005 18:00:35 +1000 (EST) (envelope-from peter@server.vk2pj.dyndns.org) Received: (from peter@localhost) by server.vk2pj.dyndns.org (8.13.1/8.13.1/Submit) id j4G80VUu021453; Mon, 16 May 2005 18:00:31 +1000 (EST) (envelope-from peter) Date: Mon, 16 May 2005 18:00:31 +1000 From: Peter Jeremy To: Nate Lawson Message-ID: <20050516080031.GD34537@server.vk2pj.dyndns.org> References: <97079.1116154766@critter.freebsd.dk> <4287AD84.6070600@root.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4287AD84.6070600@root.org> User-Agent: Mutt/1.4.2.1i cc: src-committers@freebsd.org cc: Jacques Vidrine cc: cvs-src@freebsd.org cc: cvs-all@freebsd.org cc: Poul-Henning Kamp cc: Colin Percival Subject: Re: cvs commit: src/sys/amd64/amd64 mp_machdep.csrc/sys/amd64/include cpufunc.h src/sys/i386/i386 mp_machdep.c src/sys/i386/include cpufunc.h X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 16 May 2005 08:00:41 -0000 On Sun, May 15, 2005 at 01:13:56PM -0700, Nate Lawson wrote: >My point was that FreeBSD (like most general-purpose OS) has many timing >channels that are comparably as effective for an attacker as HTT. If you take the bandwidth of the timing channel into account, I don't believe there are any other timing channels that come anywhere near the HTT attack. Maybe Colin has a better idea of what other timing channels exist and how they compare to HTT. >Disabling HTT does not significantly reduce an attacker's likelihood of >success since they can just use another timing channel. However, it >does disable a useful feature. Are we going to disable SMP next? How useful is HTT on FreeBSD? FreeBSD does not have a HTT-aware scheduler at present and I don't believe there are even any plans to make either scheduler HTT-aware. Without this, you only gain a benefit if you are running fairly specific workloads. Peter