Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Here we have another kind of deviation from the default case -
a difference between exporting functions and non-functions.
EXPORT_DATA_SYMBOL... is really different from EXPORT_SYMBOL...
on ia64, and we need to use the right one when moving exports
from *.c where C compiler has the required information to
*.S, where we need to supply it manually.
parisc64 will be another one like that.
Tested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
All the ia64 pvops code is now dead code since both
xen and kvm support have been ripped out [0] [1]. Just
that no one had troubled to rip this stuff out. The only
useful remaining pieces were the old pvops docs but that
was recently also generalized and moved out from ia64 [2].
This has been run time tested on an ia64 Madison system.
[0] 003f7de625 "KVM: ia64: remove" since v3.19-rc1
[1] d52eefb47d "ia64/xen: Remove Xen support for ia64" since v3.14-rc1
[2] "virtual: Documentation: simplify and generalize paravirt_ops.txt"
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
We would want to use number of page table level to define mm_struct.
Let's expose it as CONFIG_PGTABLE_LEVELS.
We need to define PGTABLE_LEVELS before sourcing init/Kconfig:
arch/Kconfig will define default value and it's sourced from init/Kconfig.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
April 2014 Itanium processor specification update:
http://www.intel.com/content/www/us/en/processors/itanium/itanium-specification-update.html
describes this erratum:
=========================================================================
237. Under a complex set of conditions, store to load forwarding for a
sub 8-byte load may complete incorrectly
Problem: A load instruction may complete incorrectly when a code sequence
using 4-byte or smaller load and store operations to the same address
is executed in combination with specific timing of all the following
concurrent conditions: store to load forwarding, alignment checking
enabled, a mis-predicted branch, and complex cache utilization activity.
Implication: The affected sub 8-byte instruction may complete
incorrectly resulting in unpredictable system behavior. There is an
extremely low probability of exposure due to the significant number of
complex microarchitectural concurrent conditions required to encounter
the erratum.
Workaround: Set PSR.ac = 0 to completely avoid the erratum. Disabling
Hyper-Threading will significantly reduce exposure to the conditions
that contribute to encountering the erratum.
Status: See the Summary Table of Changes for the affected steppings.
=========================================================================
[Table of changes essentially lists all models from McKinley to Tukwila]
The PSR.ac bit controls whether the processor will always generate
an unaligned reference trap (0x5a00) for a misaligned data access
(when PSR.ac=1) or if it will let the access succeed when running
on a cpu that implements logic to handle some unaligned accesses.
Way back in 2008 in commit b704882e70
[IA64] Rationalize kernel mode alignment checking
we made the decision to always enable strict checking. We were
already doing so in trap/interrupt context because the common
preamble code set this bit - but the rest of supervisor code
(and by inheritance user code) ran with PSR.ac=0.
We now reverse that decision and set PSR.ac=0 everywhere in the
kernel (also inherited by user processes). This will avoid the
erratum using the method described in the Itanium specification
update. Net effect for users is that the processor will handle
unaligned access when it can (typically with a tiny performance
bubble in the pipeline ... but much less invasive than taking a
trap and having the OS perform the access).
Signed-off-by: Tony Luck <tony.luck@intel.com>
If we want to stop the tick further idle, we need to be
able to account the cputime without using the tick.
Virtual based cputime accounting solves that problem by
hooking into kernel/user boundaries.
However implementing CONFIG_VIRT_CPU_ACCOUNTING require
low level hooks and involves more overhead. But we already
have a generic context tracking subsystem that is required
for RCU needs by archs which plan to shut down the tick
outside idle.
This patch implements a generic virtual based cputime
accounting that relies on these generic kernel/user hooks.
There are some upsides of doing this:
- This requires no arch code to implement CONFIG_VIRT_CPU_ACCOUNTING
if context tracking is already built (already necessary for RCU in full
tickless mode).
- We can rely on the generic context tracking subsystem to dynamically
(de)activate the hooks, so that we can switch anytime between virtual
and tick based accounting. This way we don't have the overhead
of the virtual accounting when the tick is running periodically.
And one downside:
- There is probably more overhead than a native virtual based cputime
accounting. But this relies on hooks that are already set anyway.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Disintegrate asm/system.h for IA64.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Tony Luck <tony.luck@intel.com>
cc: linux-ia64@vger.kernel.org
* 'for-35' of git://repo.or.cz/linux-kbuild: (81 commits)
kbuild: Revert part of e8d400a to resolve a conflict
kbuild: Fix checking of scm-identifier variable
gconfig: add support to show hidden options that have prompts
menuconfig: add support to show hidden options which have prompts
gconfig: remove show_debug option
gconfig: remove dbg_print_ptype() and dbg_print_stype()
kconfig: fix zconfdump()
kconfig: some small fixes
add random binaries to .gitignore
kbuild: Include gen_initramfs_list.sh and the file list in the .d file
kconfig: recalc symbol value before showing search results
.gitignore: ignore *.lzo files
headerdep: perlcritic warning
scripts/Makefile.lib: Align the output of LZO
kbuild: Generate modules.builtin in make modules_install
Revert "kbuild: specify absolute paths for cscope"
kbuild: Do not unnecessarily regenerate modules.builtin
headers_install: use local file handles
headers_check: fix perl warnings
export_report: fix perl warnings
...
This has been broken since May 2008 when Al Viro killed altroot support.
Since nobody has complained, it would appear that there are no users of
this code (A plausible theory since the main OSVs that support ia64 prefer
to use the IA32-EL software emulation).
Signed-off-by: Tony Luck <tony.luck@intel.com>
When CONFIG_SMP=n, three instruction in ivt.S were missed to paravirtualize.
paravirtualize them.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Recent kernels are not booting on some HP systems (though
it does boot on others). James and Willy reported the
problem. James did the bisection to find the commit
that caused the problem:
498c517047.
[IA64] pvops: paravirtualize ivt.S
Two instructions were wrongly paravirtualized such that
_FROM_ macro had been used where _TO_ was intended
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "Wilcox, Matthew R" <matthew.r.wilcox@intel.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>
move interrupt, page_fault, non_syscall, dispatch_unaligned_handler and
dispatch_to_fault_handler to avoid lack of instructin space.
The change set 4dcc29e157 bloated
SAVE_MIN_WITH_COVER, SAVE_MIN_WITH_COVER_R19 so that it bloated the
functions which uses those macros.
In the native case, only dispatch_illegal_op_fault had to be moved.
When paravirtualized case the all functions which use the macros need
to be moved to avoid the lack of space.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>
paravirtualize ivt.S which implements fault handler in hand written
assembly code.
They includes sensitive or performance critical privileged instructions.
So they need paravirtualization.
Cc: Keith Owens <kaos@ocs.com.au>
Cc: tgingold@free.fr
Cc: Akio Takebe <takebe_akio@jp.fujitsu.com>
Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Problem: An application violating the architectural rules regarding
operation dependencies and having specific Register Stack Engine (RSE)
state at the time of the violation, may result in an illegal operation
fault and invalid RSE state. Such faults may initiate a cascade of
repeated illegal operation faults within OS interruption handlers.
The specific behavior is OS dependent.
Implication: An application causing an illegal operation fault with
specific RSE state may result in a series of illegal operation faults
and an eventual OS stack overflow condition.
Workaround: OS interruption handlers that switch to kernel backing
store implement a check for invalid RSE state to avoid the series
of illegal operation faults.
The core of the workaround is the RSE_WORKAROUND code sequence
inserted into each invocation of the SAVE_MIN_WITH_COVER and
SAVE_MIN_WITH_COVER_R19 macros. This sequence includes hard-coded
constants that depend on the number of stacked physical registers
being 96. The rest of this patch consists of code to disable this
workaround should this not be the case (with the presumption that
if a future Itanium processor increases the number of registers, it
would also remove the need for this patch).
Move the start of the RBS up to a mod32 boundary to avoid some
corner cases.
The dispatch_illegal_op_fault code outgrew the spot it was
squatting in when built with this patch and CONFIG_VIRT_CPU_ACCOUNTING=y
Move it out to the end of the ivt.
Signed-off-by: Tony Luck <tony.luck@intel.com>
This patch implements VIRT_CPU_ACCOUNTING for ia64,
which enable us to use more accurate cpu time accounting.
The VIRT_CPU_ACCOUNTING is an item of kernel config, which s390
and powerpc arch have. By turning this config on, these archs
change the mechanism of cpu time accounting from tick-sampling
based one to state-transition based one.
The state-transition based accounting is done by checking time
(cycle counter in processor) at every state-transition point,
such as entrance/exit of kernel, interrupt, softirq etc.
The difference between point to point is the actual time consumed
during in the state. There is no doubt about that this value is
more accurate than that of tick-sampling based accounting.
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Instead of pinning per-cpu TLB into a DTR, use DTC. This will free up
one TLB entry for application, or even kernel if access pattern to
per-cpu data area has high temporal locality.
Since per-cpu is mapped at the top of region 7 address, we just need to
add special case in alt_dtlb_miss. The physical address of per-cpu data
is already conveniently stored in IA64_KR(PER_CPU_DATA). Latency for
alt_dtlb_miss is not affected as we can hide all the latency. It was
measured that alt_dtlb_miss handler has 23 cycles latency before and
after the patch.
The performance effect is massive for applications that put lots of tlb
pressure on CPU. Workload environment like database online transaction
processing or application uses tera-byte of memory would benefit the most.
Measurement with industry standard database benchmark shown an upward
of 1.6% gain. While smaller workloads like cpu, java also showing small
improvement.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Memory errors encountered by user applications may surface
when the CPU is running in kernel context. The current code
will not attempt recovery if the MCA surfaces in kernel
context (privilage mode 0). This patch adds a check for cases
where the user initiated the load that surfaces in kernel
interrupt code.
An example is a user process lauching a load from memory
and the data in memory had bad ECC. Before the bad data
gets to the CPU register, and interrupt comes in. The
code jumps to the IVT interrupt entry point and begins
execution in kernel context. The process of saving the
user registers (SAVE_REST) causes the bad data to be loaded
into a CPU register, triggering the MCA. The MCA surfaces in
kernel context, even though the load was initiated from
user context.
As suggested by David and Tony, this patch uses an exception
table like approach, puting the tagged recovery addresses in
a searchable table. One difference from the exception table
is that MCAs do not surface in precise places (such as with
a TLB miss), so instead of tagging specific instructions,
address ranges are registers. A single macro is used to do
the tagging, with the input parameter being the label
of the starting address and the macro being the ending
address. This limits clutter in the code.
This patch only tags one spot, the interrupt ivt entry.
Testing showed that spot to be a "heavy hitter" with
MCAs surfacing while saving user registers. Other spots
can be added as needed by adding a single macro.
Signed-off-by: Russ Anderson (rja@sgi.com)
Signed-off-by: Tony Luck <tony.luck@intel.com>
A pte may be zapped by the swapper, exiting process, unmapping or page
migration while the accessed or dirty bit handers are about to run. In that
case the accessed bit or dirty is set on an zeroed pte which leads the VM to
conclude that this is a swap pte. This may lead to
- Messages from the vm like
swap_free: Bad swap file entry 4000000000000000
- Processes being aborted
swap_dup: Bad swap file entry 4000000000000000
VM: killing process ....
Page migration is particular suitable for the creation of this race since
it needs to remove and restore page table entries.
The fix here is to check for the present bit and simply not update
the pte if the page is not present anymore. If the page is not present
then the fault handler should run next which will take care of the problem
by bringing the page back and then mark the page dirty or move it onto the
active list.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
unaligned_access does fetch cr.ipsr, then calls
dispatch_unaligned_handler, but dispatch_unaligned_handler fetches
cr.ipsr again, so delete the first one.
Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Polish the comments specifically in vhpt_miss and nested_dtlb_miss
handlers. I think it's better to explicitly name each page table
level with its name instead of numerically name them. i.e., use
pgd, pud, pmd, and pte instead of referring as L1, L2, L3 etc.
Along the line, remove some magic number in the comments like:
"PTA + (((IFA(61,63) << 7) | IFA(33,39))*8)". No code change at
all, pure comment update. Feel free to shoot anything you have,
darts or tomahawk cruise missile. I will duck behind a bunker ;-)
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Robin Holt <holt@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
From source code inspection, I think there is a bug with 4 level
page table with vhpt_miss handler. In the code path of rechecking
page table entry against previously read value after tlb insertion,
*pte value in register r18 was overwritten with value newly read
from pud pointer, render the check of new *pte against previous
*pte completely wrong. Though the bug is none fatal and the penalty
is to purge the entry and retry. For functional correctness, it
should be fixed. The fix is to use a different register so new
*pud don't trash *pte. (btw, the comments in the cmp statement is
wrong as well, which I will address in the next patch).
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This patch introduces 4-level page tables to ia64. I have run
some benchmarks and found nothing interesting. Performance has
consistently fallen within the noise range.
It also introduces a config option (setting the default to 3
levels). The config option prevents having 4 level page
tables with 64k base page size.
Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Delete obsolete stuff from arch Makefile
Rename file to asm-offsets.h
The trick used in the arch Makefile to circumvent the circular
dependency is kept.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
This patch greatly speeds up the handling of lfetch.fault instructions
which result in NaT consumption. Due to the NaT-page mapped at address
0, this is guaranteed to happen when lfetch.fault'ing a NULL pointer.
With this patch in place, we can even define prefetch()/prefetchw() as
lfetch.fault without significant performance degradation. More
importantly, it allows compilers to be more aggressive with using
lfetch.fault on pointers that might be NULL.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
The nested_dtlb_miss handler currently does not handle fault from
hugetlb address correctly. It walks the page table assuming PAGE_SIZE.
Thus when taking a fault triggered from hugetlb address, it would not
calculate the pgd/pmd/pte address correctly and thus result an incorrect
invocation of ia64_do_page_fault(). In there, kernel will signal SIGBUS
and application dies (The faulting address is perfectly legal and we
have a valid pte for the corresponding user hugetlb address as well).
This patch fix the described kernel bug. Since nested_dtlb_miss is a
rare event and a slow path anyway, I'm making the change without #ifdef
CONFIG_HUGETLB_PAGE for code readability. Tony, please apply.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This patch reorganizes break_fault() to optimistically assume that a
system-call is being performed from user-space (which is almost always
the case). If it turns out that (a) we're not being called due to a
system call or (b) we're being called from within the kernel, we fixup
the no-longer-valid assumptions in non_syscall() and .break_fixup(),
respectively.
With this approach, there are 3 major phases:
- Phase 1: Read various control & application registers, in
particular the current task pointer from AR.K6.
- Phase 2: Do all memory loads (load system-call entry,
load current_thread_info()->flags, prefetch
kernel register-backing store) and switch
to kernel register-stack.
- Phase 3: Call ia64_syscall_setup() and invoke
syscall-handler.
Good for 26-30 cycles of improvement on break-based syscall-path.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Using stf8 seemed like a clever idea at the time, but stf8 forces
the cache-line to be invalidated in the L1D (if it happens to be
there already). This patch eliminates a guaranteed L1D cache-miss
and, by itself, is good for a 1-2 cycle improvement for heavy-weight
syscalls.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Greg Kroah-Hartman