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

[Pavel Machek <pavel@ucw.cz>]

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.

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