From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755461AbZGEUXd (ORCPT ); Sun, 5 Jul 2009 16:23:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753472AbZGEUXY (ORCPT ); Sun, 5 Jul 2009 16:23:24 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:57432 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753190AbZGEUXX (ORCPT ); Sun, 5 Jul 2009 16:23:23 -0400 Date: Sun, 5 Jul 2009 22:23:16 +0200 From: Pavel Machek To: Ingo Molnar Cc: Joseph Cihula , linux-kernel@vger.kernel.org, arjan@linux.intel.com, hpa@zytor.com, andi@firstfloor.org, chrisw@sous-sol.org, jmorris@namei.org, jbeulich@novell.com, peterm@redhat.com, gang.wei@intel.com, shane.wang@intel.com Subject: Re: [RFC v6][PATCH 4/4] intel_txt: force IOMMU on for Intel(R) TXT launch Message-ID: <20090705202316.GH17910@elf.ucw.cz> References: <4A4ACA6E.6080702@intel.com> <20090702213013.GC1419@ucw.cz> <20090703082111.GD21833@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090703082111.GD21833@elte.hu> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 2009-07-03 10:21:11, Ingo Molnar wrote: > > * Pavel Machek wrote: > > > > > On Tue 2009-06-30 19:31:10, Joseph Cihula wrote: > > > The tboot module will DMA protect all of memory in order to ensure the that > > > kernel will be able to initialize without compromise (from DMA). Consequently, > > > the kernel must enable Intel(R) Virtualization Technology for Directed I/O > > > (VT-d or Intel IOMMU) in order to replace this broad protection with the > > > appropriate page-granular protection. Otherwise DMA devices will be unable > > > to read or write from memory and the kernel will eventually panic. > > > > > > Because runtime IOMMU support is configurable by command line options, this > > > patch will force it to be enabled regardless of the options specified, and will > > > log a message if it was required to force it on. > > > > > > > > > dmar.c | 7 +++++++ > > > intel-iommu.c | 17 +++++++++++++++-- > > > 2 files changed, 22 insertions(+), 2 deletions(-) > > > > > > Signed-off-by: Joseph Cihula > > > Signed-off-by: Shane Wang > > > > NAK. Breaks user expectations, misses docs updates. > > What's your proposed solution? If an incompatible IOMMU option is > specified should the kernel to disable TXT and panic? Yes. ...and whether we decide one way or another, it needs to be documented.a Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html