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

[Pavel Machek <pavel@ucw.cz>]

On Fri 2009-07-03 10:21:11, Ingo Molnar wrote:
> 
> * Pavel Machek <pavel@ucw.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@intel.com>
> > > Signed-off-by: Shane Wang <shane.wang@intel.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?

Yes.

...and whether we decide one way or another, it needs to be documented.a

											Pavel
-- 
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