From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933843AbWLAPJa (ORCPT ); Fri, 1 Dec 2006 10:09:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S935044AbWLAPJa (ORCPT ); Fri, 1 Dec 2006 10:09:30 -0500 Received: from adelie.ubuntu.com ([82.211.81.139]:31689 "EHLO adelie.ubuntu.com") by vger.kernel.org with ESMTP id S933843AbWLAPJa (ORCPT ); Fri, 1 Dec 2006 10:09:30 -0500 Subject: Re: [PATCH 1/4] [x86] Add command line option to enable/disable hyper-threading. From: Ben Collins To: Arjan van de Ven Cc: Pavel Machek , linux-kernel@vger.kernel.org, torvalds@osdl.org In-Reply-To: <1164983529.3233.73.camel@laptopd505.fenrus.org> References: <11648607683157-git-send-email-bcollins@ubuntu.com> <11648607733630-git-send-email-bcollins@ubuntu.com> <20061201132918.GB4239@ucw.cz> <1164980500.5257.922.camel@gullible> <1164983529.3233.73.camel@laptopd505.fenrus.org> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Fri, 01 Dec 2006 10:09:17 -0500 Message-Id: <1164985757.5257.933.camel@gullible> Mime-Version: 1.0 X-Mailer: Evolution 2.8.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2006-12-01 at 15:32 +0100, Arjan van de Ven wrote: > > > > The idea is that we want our users to be able to use hyper-threading, > > but we don't want it on by default. > > Hi, > > can I ask why not? I'm just basing this on the history of the patch, which preceeds me, so if this is incorrect, please don't blame me for misinformation :) The original patch claims that hyper-threading opens the user up to some sort of security risk involving hardware limitations in protecting memory across the threads. I can't recall all the details. If this is wrong, I'm more than happy to just drop the whole damn patch.