From owner-freebsd-arch@FreeBSD.ORG Sun May 22 01:04:22 2005 Return-Path: X-Original-To: freebsd-arch@freebsd.org Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B734316A41C; Sun, 22 May 2005 01:04:22 +0000 (GMT) (envelope-from marcel@xcllnt.net) Received: from ns1.xcllnt.net (209-128-86-226.bayarea.net [209.128.86.226]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6F06243D1F; Sun, 22 May 2005 01:04:22 +0000 (GMT) (envelope-from marcel@xcllnt.net) Received: from [192.168.4.250] (dhcp50.pn.xcllnt.net [192.168.4.250]) by ns1.xcllnt.net (8.13.3/8.13.3) with ESMTP id j4M14MGa023025; Sat, 21 May 2005 18:04:22 -0700 (PDT) (envelope-from marcel@xcllnt.net) In-Reply-To: <428FD710.4060200@freebsd.org> References: <428FC00B.3080909@freebsd.org> <428FD710.4060200@freebsd.org> Mime-Version: 1.0 (Apple Message framework v622) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <9e8314b53980a379445cc8c07086901d@xcllnt.net> Content-Transfer-Encoding: 7bit From: Marcel Moolenaar Date: Sat, 21 May 2005 18:04:23 -0700 To: Colin Percival X-Mailer: Apple Mail (2.622) cc: freebsd-arch@freebsd.org Subject: Re: Scheduler fixes for hyperthreading X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 22 May 2005 01:04:22 -0000 On May 21, 2005, at 5:49 PM, Colin Percival wrote: > Marcel Moolenaar wrote: >> On May 21, 2005, at 4:11 PM, Colin Percival wrote: >>> The following must be done before hyperthreading is re-enabled: >>> [snip] >> >> Maybe it's a better idea to describe the problem in much more >> detail, rather than dictate what you want someone else to do? >> A pointer to where the problem is described/discussed would >> do. > > The problem is described in my paper "Cache missing for fun and > profit": > http://www.daemonology.net/papers/htt.pdf Thanks. > Put simply, threads which share a processor core can monitor each > others' > memory access patterns, so we need to ensure that such co-scheduling > never > happens between threads which have different privileges. I'll be studying your paper to see if it can be shown that the HT implementation in Itanium is affected as well. If not, any solution must be sufficiently machine dependent. > The reason I cut through to explaining what needed to be done is that > I discussed this at length with several people from the FreeBSD > security > team before and during BSDCan; but these discussions were obviously not > public, so I can't give a reference to them. I can only assume that the discussion was i386 centric (as this is typically the case). Hence my request for a problem description. -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net