Add a description of the cpuinfo_cur_freq policy attribute in sysfs
to the cpufreq documentation under Documentation/admin-guide/pm/ as
it is missing after commit 2a0e4927 (cpufreq: User/admin
documentation update and consolidation) that overlooked it.

Fixes: 2a0e4927 (cpufreq: User/admin documentation update and consolidation)
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>

Commit 20b2f52b ("numa: add CONFIG_MOVABLE_NODE for
movable-dedicated node") has introduced CONFIG_MOVABLE_NODE without a
good explanation on why it is actually useful.

It makes a lot of sense to make movable node semantic opt in but we
already have that because the feature has to be explicitly enabled on
the kernel command line.  A config option on top only makes the
configuration space larger without a good reason.  It also adds an
additional ifdefery that pollutes the code.

Just drop the config option and make it de-facto always enabled.  This
shouldn't introduce any change to the semantic.

Link: http://lkml.kernel.org/r/20170529114141.536-3-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NReza Arbab <arbab@linux.vnet.ibm.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Kani Toshimitsu <toshi.kani@hpe.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Some hardened environments want to build kernels with slab_nomerge
already set (so that they do not depend on remembering to set the kernel
command line option).  This is desired to reduce the risk of kernel heap
overflows being able to overwrite objects from merged caches and changes
the requirements for cache layout control, increasing the difficulty of
these attacks.  By keeping caches unmerged, these kinds of exploits can
usually only damage objects in the same cache (though the risk to
metadata exploitation is unchanged).

Link: http://lkml.kernel.org/r/20170620230911.GA25238@beastSigned-off-by: NKees Cook <keescook@chromium.org>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: David Windsor <dave@nullcore.net>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: David Windsor <dave@nullcore.net>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Daniel Mack <daniel@zonque.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit f8475cef "x86: use common aperfmperf_khz_on_cpu() to
calculate KHz using APERF/MPERF" modified the way the scaling_cur_freq
cpufreq policy attribute in sysfs is handled on contemporary
Intel-based x86 systems, so update the documentation to reflect
that change.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

After commit 82b4e03e (intel_pstate: skip scheduler hook when in
"performance" mode) get_target_pstate_use_performance() and
get_target_pstate_use_cpu_load() are never called if scaling_governor
is "performance", so drop the CPUFREQ_POLICY_PERFORMANCE checks from
them as they will never trigger anyway.

Moreover, the documentation needs to be updated to reflect the change
made by the above commit, so do that too.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

Two table problems caused the PDF build to fail:

 - Evidently multirow cells are not appreciated in table headers,
   so remove such from the "CS Rows" table.

 - The logging message structure table was incorrectly formatted,
   with two "+" instead of "|".  The HTML build is forgiving of such
   things, but PDF is not.
Acked-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Another place in lib/Kconfig.debug was already fixed in commit f8998c22
("lib/Kconfig.debug: correct documentation paths").

Fixes: 9d85025b ("docs-rst: create an user's manual book")
Signed-off-by: NSteffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

The builtin "ima_appraise_tcb" policy should require file signatures for
at least a few of the hooks (eg. kernel modules, firmware, and the kexec
kernel image), but changing it would break the existing userspace/kernel
ABI.

This patch defines a new builtin policy named "secure_boot", which
can be specified on the "ima_policy=" boot command line, independently
or in conjunction with the "ima_appraise_tcb" policy, by specifing
ima_policy="appraise_tcb | secure_boot".  The new appraisal rules
requiring file signatures will be added prior to the "ima_appraise_tcb"
rules.
Signed-off-by: NMimi Zohar <zohar@linux.vnet.ibm.com>

Changelog:
- Reference secure boot in the new builtin policy name. (Thiago Bauermann)

Add support for providing multiple builtin policies on the "ima_policy="
boot command line.  Use "|" as the delimitor separating the policy names.
Signed-off-by: NMimi Zohar <zohar@linux.vnet.ibm.com>

This implements an earlycon for Actions Semi S500/S900 SoCs.

Based on LeMaker linux-actions tree.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.
Original-patch-by: NOleg Nesterov <oleg@redhat.com>
Original-patch-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NHugh Dickins <hughd@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now that we're able to safely handle common sysreg access, let's
give the user the opportunity to enable it by passing a specific
command-line option (vgic_v3.common_trap).
Tested-by: NAlexander Graf <agraf@suse.de>
Acked-by: NDavid Daney <david.daney@cavium.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Acked-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Now that we're able to safely handle Group-0 sysreg access, let's
give the user the opportunity to enable it by passing a specific
command-line option (vgic_v3.group0_trap).
Tested-by: NAlexander Graf <agraf@suse.de>
Acked-by: NDavid Daney <david.daney@cavium.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Now that we're able to safely handle Group-1 sysreg access, let's
give the user the opportunity to enable it by passing a specific
command-line option (vgic_v3.group1_trap).
Tested-by: NAlexander Graf <agraf@suse.de>
Acked-by: NDavid Daney <david.daney@cavium.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Acked-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Add coresight_cpu_debug.enable to kernel-parameters.txt, this flag is
used to enable/disable the CPU sampling based debugging.
Signed-off-by: NLeo Yan <leo.yan@linaro.org>
Signed-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Since there are no such tool yet that handles all the low-level details
of connecting devices and upgrading their firmware, add a small document
that shows how the Thunderbolt bus can be used directly from command
line.
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: NYehezkel Bernat <yehezkel.bernat@intel.com>
Reviewed-by: NMichael Jamet <michael.jamet@intel.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NAndreas Noever <andreas.noever@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The RCU_TORTURE_TEST_SLOW_PREINIT, RCU_TORTURE_TEST_SLOW_PREINIT_DELAY,
RCU_TORTURE_TEST_SLOW_PREINIT_DELAY, RCU_TORTURE_TEST_SLOW_INIT,
RCU_TORTURE_TEST_SLOW_INIT_DELAY, RCU_TORTURE_TEST_SLOW_CLEANUP,
and RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY Kconfig options are only
useful for torture testing, and there are the rcutree.gp_cleanup_delay,
rcutree.gp_init_delay, and rcutree.gp_preinit_delay kernel boot parameters
that rcutorture can use instead.  The effect of these parameters is to
artificially slow down grace period initialization and cleanup in order
to make some types of race conditions happen more often.

This commit therefore simplifies Tree RCU a bit by removing the Kconfig
options and adding the corresponding kernel parameters to rcutorture's
.boot files instead.  However, this commit also leaves out the kernel
parameters for TREE02, TREE04, and TREE07 in order to have about the
same number of tests slowed as not slowed.  TREE01, TREE03, TREE05,
and TREE06 are slowed, and the rest are not slowed.
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

If a given CPU never happens to ever start an SRCU grace period, the
grace-period sequence counter might wrap.  If this CPU were to decide to
finally start a grace period, the state of its sdp->srcu_gp_seq_needed
might make it appear that it has already requested this grace period,
which would prevent starting the grace period.  If no other CPU ever started
a grace period again, this would look like a grace-period hang.  Even
if some other CPU took pity and started the needed grace period, the
leaf rcu_node structure's ->srcu_data_have_cbs field won't have record
of the fact that this CPU has a callback pending, which would look like
a very localized grace-period hang.

This might seem very unlikely, but SRCU grace periods can take less than
a microsecond on small systems, which means that overflow can happen
in much less than an hour on a 32-bit embedded system.  And embedded
systems are especially likely to have long-term idle CPUs.  Therefore,
it makes sense to prevent this scenario from happening.

This commit therefore scans each srcu_data structure occasionally,
with frequency controlled by the srcutree.counter_wrap_check kernel
boot parameter.  This parameter can be set to something like 255
in order to exercise the counter-wrap-prevention code.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit adds a writer_holdoff boot parameter to rcuperf, which is
intended to be used to test Tree SRCU's auto-expediting.  This
boot parameter is in microseconds, and defaults to zero (that is,
disabled).  Set it to a bit larger than srcutree.exp_holdoff,
keeping the nanosecond/microsecond conversion, to force Tree SRCU
to auto-expedite more aggressively.

This commit also adds documentation for this parameter, and fixes some
alphabetization while in the neighborhood.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit upgrades rcuperf so that it can do performance testing on
asynchronous grace-period primitives such as call_srcu().  There is
a new rcuperf.gp_async module parameter that specifies this new behavior,
with the pre-existing rcuperf.gp_exp testing expedited grace periods such as
synchronize_rcu_expedited, and with the default being to test synchronous
non-expedited grace periods such as synchronize_rcu().

There is also a new rcuperf.gp_async_max module parameter that specifies
the maximum number of outstanding callbacks per writer kthread, defaulting
to 1,000.  When this limit is exceeded, the writer thread invokes the
appropriate flavor of rcu_barrier() to wait for callbacks to drain.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Removed the redundant initialization noted by Arnd Bergmann. ]

Provide a dt_cpu_ftrs= cmdline option to disable the dt_cpu_ftrs CPU
feature discovery, and fall back to the "cputable" based version.

Also allow control of advertising unknown features to userspace and
with this parameter, and remove the clunky CONFIG option.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
[mpe: Add explicit early check of bootargs in dt_cpu_ftrs_init()]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

In commit:

  9710f581 ("x86, mm: Let "memmap=" take more entries one time")

... 'memmap=' was changed to adopt multiple, comma delimited values in a
single entry, so update the related description.

In the special case of only specifying size value without an offset,
like memmap=nn[KMG], memmap behaves similarly to mem=nn[KMG], so update
it too here.

Furthermore, for memmap=nn[KMG]$ss[KMG], an escape character needs be added
before '$' for some bootloaders. E.g in grub2, if we specify memmap=100M$5G
as suggested by the documentation, "memmap=100MG" gets passed to the kernel.

Clarify all this.
Signed-off-by: NBaoquan He <bhe@redhat.com>
Acked-by: NKees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Cc: douly.fnst@cn.fujitsu.com
Cc: dyoung@redhat.com
Cc: m.mizuma@jp.fujitsu.com
Link: http://lkml.kernel.org/r/1494654390-23861-4-git-send-email-bhe@redhat.com
[ Various spelling fixes. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Adjusts for ReST markup and moves under LSM admin guide.
Acked-by: NCasey Schaufler <casey@schaufler-ca.com>
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Adjusts for ReST markup and moves under LSM admin guide.
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Adjusts for ReST markup and moves under LSM admin guide.
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Adjusts for ReST markup and moves under LSM admin guide.

Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Adjusts for ReST markup and moves under LSM admin guide.
Acked-by: NJohn Johansen <john.johansen@canonical.com>
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Adjusts for ReST markup and moves under LSM admin guide.

Cc: Paul Moore <paul@paul-moore.com>
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

The existing LSM.txt file covered both usage and development, so split
this into two files, one under admin-guide and one under kernel
development.

Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Vhost-vsock is a software device so there is no probe call that causes
the driver to register its misc char device node.  This creates a
chicken and egg problem: userspace applications must open
/dev/vhost-vsock to use the driver but the file doesn't exist until the
kernel module has been loaded.

Use the devname modalias mechanism so that /dev/vhost-vsock is created
at boot.  The vhost_vsock kernel module is automatically loaded when the
first application opens /dev/host-vsock.

Note that the "reserved for local use" range in
Documentation/admin-guide/devices.txt is incorrect.  The userio driver
already occupies part of that range.  I've updated the documentation
accordingly.

Cc: device@lanana.org
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

DocBook is mentioned several times at the documentation. Update
the obsolete references from it at the DocBook.
Acked-by: NSeongJae Park <sj38.park@gmail.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

Add a document describing the current behavior and user space
interface of the intel_pstate driver in the RST format and
drop the existing outdated intel_pstate.txt document.

Also update admin-guide/pm/cpufreq.rst with proper RST references
to the new intel_pstate.rst document.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

FTP services were shutdown some weeks ago, so the FTP URL
does not work anymore. Fix this by replacing it with
corresponding HTTPS URL.
Signed-off-by: NMichael Heimpold <michael.heimpold@i2se.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

The Marvell Armada 3700 UART uses "ar3700_uart" for its earlycon name.
Adjust documentation to match the code.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

The AVR32 architecture support has been removed from the Linux kernel,
hence remove all references to it from Documentation.
Signed-off-by: NHans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Signed-off-by: NHåvard Skinnemoen <hskinnemoen@gmail.com>
Signed-off-by: NNicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: NBoris Brezillon <boris.brezillon@free-electrons.com>

On small systems, in the absence of readers, expedited SRCU grace
periods can complete in less than a microsecond.  This means that an
eight-CPU system can have all CPUs doing synchronize_srcu() in a tight
loop and almost always expedite.  This might actually be desirable in
some situations, but in general it is a good way to needlessly burn
CPU cycles.  And in those situations where it is desirable, your friend
is the function synchronize_srcu_expedited().

For other situations, this commit adds a kernel parameter that specifies
a holdoff between completing the last SRCU grace period and auto-expediting
the next.  If the next grace period starts before the holdoff expires,
auto-expediting is disabled.  The holdoff is 50 microseconds by default,
and can be tuned to the desired number of nanoseconds.  A value of zero
disables auto-expediting.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: NMike Galbraith <efault@gmx.de>

IOMMU harms performance signficantly when we run very fast networking
workloads. It's 40GB networking doing XDP test. Software overhead is
almost unaware, but it's the IOTLB miss (based on our analysis) which
kills the performance. We observed the same performance issue even with
software passthrough (identity mapping), only the hardware passthrough
survives. The pps with iommu (with software passthrough) is only about
~30% of that without it. This is a limitation in hardware based on our
observation, so we'd like to disable the IOMMU force on, but we do want
to use TBOOT and we can sacrifice the DMA security bought by IOMMU. I
must admit I know nothing about TBOOT, but TBOOT guys (cc-ed) think not
eabling IOMMU is totally ok.

So introduce a new boot option to disable the force on. It's kind of
silly we need to run into intel_iommu_init even without force on, but we
need to disable TBOOT PMR registers. For system without the boot option,
nothing is changed.
Signed-off-by: NShaohua Li <shli@fb.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>

In Documentation/process/4.Coding.rst there were a couple of paragraphs
that spilled over the 80 character line length. This was likely caused
when the document was converted to reStructuredText. Re-flow the
paragraphs and make the document references proper reStructuredText
:ref: links.

This also adds the appropriate reStructuredText file heading to
kernel-parameters.rst as referenced by the kernel-parameters link in
this patch.
Signed-off-by: NAndrew Clayton <andrew@digital-domain.net>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

The objlayout code has been in the tree, but it's been unmaintained and
no server product for it actually ever shipped.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

The IOMMU core currently initialises the default domain for each group
to IOMMU_DOMAIN_DMA, under the assumption that devices will use
IOMMU-backed DMA ops by default. However, in some cases it is desirable
for the DMA ops to bypass the IOMMU for performance reasons, reserving
use of translation for subsystems such as VFIO that require it for
enforcing device isolation.

Rather than modify each IOMMU driver to provide different semantics for
DMA domains, instead we introduce a command line parameter that can be
used to change the type of the default domain. Passthrough can then be
specified using "iommu.passthrough=1" on the kernel command line.
Signed-off-by: NWill Deacon <will.deacon@arm.com>