Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261442AbVENQos (ORCPT ); Sat, 14 May 2005 12:44:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262796AbVENQos (ORCPT ); Sat, 14 May 2005 12:44:48 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:8069 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S261442AbVENQom (ORCPT ); Sat, 14 May 2005 12:44:42 -0400 Subject: Re: Hyper-Threading Vulnerability From: Arjan van de Ven To: Lee Revell Cc: Alan Cox , Dave Jones , Matt Mackall , Andy Isaacson , Andi Kleen , "Richard F. Rebel" , Gabor MICSKO , Linux Kernel Mailing List , tytso@mit.edu In-Reply-To: <1116088229.8880.7.camel@mindpipe> References: <1115963481.1723.3.camel@alderaan.trey.hu> <1116009483.4689.803.camel@rebel.corp.whenu.com> <20050513190549.GB47131@muc.de> <20050513212620.GA12522@hexapodia.org> <20050513215905.GY5914@waste.org> <1116024419.20646.41.camel@localhost.localdomain> <1116025212.6380.50.camel@mindpipe> <20050513232708.GC13846@redhat.com> <1116027488.6380.55.camel@mindpipe> <1116084186.20545.47.camel@localhost.localdomain> <1116088229.8880.7.camel@mindpipe> Content-Type: text/plain Date: Sat, 14 May 2005 18:44:27 +0200 Message-Id: <1116089068.6007.13.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-4) Content-Transfer-Encoding: 7bit X-Spam-Score: 3.7 (+++) X-Spam-Report: SpamAssassin version 2.63 on pentafluge.infradead.org summary: Content analysis details: (3.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 1.1 RCVD_IN_DSBL RBL: Received via a relay in list.dsbl.org [] 2.5 RCVD_IN_DYNABLOCK RBL: Sent directly from dynamic IP address [80.57.133.107 listed in dnsbl.sorbs.net] 0.1 RCVD_IN_SORBS RBL: SORBS: sender is listed in SORBS [80.57.133.107 listed in dnsbl.sorbs.net] X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1458 Lines: 30 On Sat, 2005-05-14 at 12:30 -0400, Lee Revell wrote: > On Sat, 2005-05-14 at 16:23 +0100, Alan Cox wrote: > > On Sad, 2005-05-14 at 00:38, Lee Revell wrote: > > > Well yes but you would still have to recompile those apps. And take the > > > big performance hit from using gettimeofday vs rdtsc. Disabling HT by > > > default looks pretty good by comparison. > > > > You cannot use rdtsc for anything but rough instruction timing. The > > timers for different processors run at different speeds on some SMP > > systems, the timer rates vary as processors change clock rate nowdays. > > Rdtsc may also jump dramatically on a suspend/resume. > > > > If the app uses rdtsc then generally speaking its terminally broken. The > > only exception is some profiling tools. > > That is basically all JACK and mplayer use it for. They have RT > constraints and the tsc is used to know if we got woken up too late and > should just drop some frames. The developers are aware of the issues > with rdtsc and have chosen to use it anyway because these apps need > every ounce of CPU and cannot tolerate the overhead of gettimeofday(). then JACK is terminally broken if it doesn't have a fallback for non- rdtsc cpus. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/