linux-kernel - Re: [RFC v6][PATCH 4/4] intel_txt: force IOMMU on for Intel(R) TXT launch

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Date:	Fri, 3 Jul 2009 10:21:11 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Pavel Machek <pavel@....cz>
Cc:	Joseph Cihula <joseph.cihula@...el.com>,
	linux-kernel@...r.kernel.org, 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 v6][PATCH 4/4] intel_txt: force IOMMU on for Intel(R) TXT
	launch


* Pavel Machek <pavel@....cz> 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 <joseph.cihula@...el.com>
> > Signed-off-by: Shane Wang <shane.wang@...el.com>
> 
> 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?

	Ingo
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