linux-kernel - Re: [RFC v5][PATCH 4/4] intel_txt: force IOMMU on for Intel(R) TXT launch

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Message-ID: <20090624150536.GL1784@ucw.cz>
Date:	Wed, 24 Jun 2009 17:05:36 +0200
From:	Pavel Machek <pavel@....cz>
To:	Joseph Cihula <joseph.cihula@...el.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, arjan@...ux.intel.com,
	hpa@...or.com, andi@...stfloor.org, chrisw@...s-sol.org,
	jmorris@...ei.org, jbeulich@...ell.com, peterm@...hat.com,
	gang.wei@...el.com, shane.wang@...el.com
Subject: Re: [RFC v5][PATCH 4/4] intel_txt: force IOMMU on for Intel(R) TXT
	launch

On Mon 2009-06-22 17:41:41, 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        |    8 ++++++++
>  intel-iommu.c |   28 ++++++++++++++++++++++++++--
>  2 files changed, 34 insertions(+), 2 deletions(-)

This needs documentation. And you probably should panic the kernel if
user passes unworkable options, not override his choices.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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