If you're bisecting why your peripherals stopped working, it's
probably this CL. Specifically if you see this in your dmesg:
Unexpected global fault, this could be serious
...then it's almost certainly this CL.
Running your IOMMU-enabled peripherals with the IOMMU in bypass mode
is insecure and effectively disables the protection they provide.
There are few reasons to allow unmatched stream bypass, and even fewer
good ones.
This patch starts the transition over to make it much harder to run
your system insecurely. Expected steps:
1. By default disable bypass (so anyone insecure will notice) but make
it easy for someone to re-enable bypass with just a KConfig change.
That's this patch.
2. After people have had a little time to come to grips with the fact
that they need to set their IOMMUs properly and have had time to
dig into how to do this, the KConfig will be eliminated and bypass
will simply be disabled. Folks who are truly upset and still
haven't fixed their system can either figure out how to add
'arm-smmu.disable_bypass=n' to their command line or revert the
patch in their own private kernel. Of course these folks will be
less secure.
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
Tested-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
954a03be03