Impact: cleanup
Remove an #ifdef from kmmio_fault() - we can do this by
providing default implementations for is_kmmio_active()
and kmmio_handler(). The compiler optimizes it all away
in the !CONFIG_MMIOTRACE case.
Also, while at it, clean up mmiotrace.h a bit:
- standard header guards
- standard vertical spaces for structure definitions
No code changed (both with mmiotrace on and off in the config):
text data bss dec hex filename
2947 12 12 2971 b9b fault.o.before
2947 12 12 2971 b9b fault.o.after
Cc: Pekka Paalanen <pq@iki.fi>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: improve page fault handling robustness
The 'PF_RSVD' flag (bit 3) of the page-fault error_code is a
relatively recent addition to x86 CPUs, so the 32-bit do_fault()
implementation never had it. This flag gets set when the CPU
detects nonzero values in any reserved bits of the page directory
entries.
Extend the existing 64-bit check for PF_RSVD in do_page_fault()
to 32-bit too. If we detect such a fault then we print a more
informative oops and the pagetables.
This unifies the code some more, removes an ugly #ifdef and improves
the 32-bit page fault code robustness a bit. It slightly increases
the 32-bit kernel text size.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup
Instead of an ugly, open-coded, #ifdef-ed vm86 related legacy check
in do_page_fault(), put it into the check_v8086_mode() helper
function and merge it with an existing #ifdef.
Also, simplify the code flow a tiny bit in the helper.
No code changed:
arch/x86/mm/fault.o:
text data bss dec hex filename
2711 12 12 2735 aaf fault.o.before
2711 12 12 2735 aaf fault.o.after
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: no functionality changed
Factor out the opcode checker into a helper inline.
The code got a tiny bit smaller:
text data bss dec hex filename
4632 32 24 4688 1250 fault.o.before
4618 32 24 4674 1242 fault.o.after
And it got cleaner / easier to review as well.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup, no code changed
Clean up various small details, which can be correctness checked
automatically:
- tidy up the include file section
- eliminate unnecessary includes
- introduce show_signal_msg() to clean up code flow
- standardize the code flow
- standardize comments and other style details
- more cleanups, pointed out by checkpatch
No code changed on either 32-bit nor 64-bit:
arch/x86/mm/fault.o:
text data bss dec hex filename
4632 32 24 4688 1250 fault.o.before
4632 32 24 4688 1250 fault.o.after
the md5 changed due to a change in a single instruction:
2e8a8241e7f0d69706776a5a26c90bc0 fault.o.before.asm
c5c3d36e725586eb74f0e10692f0193e fault.o.after.asm
Because a __LINE__ reference in a WARN_ONCE() has changed.
On 32-bit a few stack offsets changed - no code size difference
nor any functionality difference.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix to prevent NMI lockup
If the page fault handler produces a WARN_ON in the modifying of
text, and the system is setup to have a high frequency of NMIs,
we can lock up the system on a failure to modify code.
The modifying of code with NMIs allows all NMIs to modify the code
if it is about to run. This prevents a modifier on one CPU from
modifying code running in NMI context on another CPU. The modifying
is done through stop_machine, so only NMIs must be considered.
But if the write causes the page fault handler to produce a warning,
the print can slow it down enough that as soon as it is done
it will take another NMI before going back to the process context.
The new NMI will perform the write again causing another print and
this will hang the box.
This patch turns off the writing as soon as a failure is detected
and does not wait for it to be turned off by the process context.
This will keep NMIs from getting stuck in this back and forth
of print outs.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: keep kernel text read only
Because dynamic ftrace converts the calls to mcount into and out of
nops at run time, we needed to always keep the kernel text writable.
But this defeats the point of CONFIG_DEBUG_RODATA. This patch converts
the kernel code to writable before ftrace modifies the text, and converts
it back to read only afterward.
The kernel text is converted to read/write, stop_machine is called to
modify the code, then the kernel text is converted back to read only.
The original version used SYSTEM_STATE to determine when it was OK
or not to change the code to rw or ro. Andrew Morton pointed out that
using SYSTEM_STATE is a bad idea since there is no guarantee to what
its state will actually be.
Instead, I moved the check into the set_kernel_text_* functions
themselves, and use a local variable to determine when it is
OK to change the kernel text RW permissions.
[ Update: Ingo Molnar suggested moving the prototypes to cacheflush.h ]
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
clean up vmi_read_cycles to use max()
Reported-b: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alok N Kataria <akataria@vmware.com>
Cc: Zach Amsden <zach@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: future-proof the split_large_page() function
Linus noticed that split_large_page() is not safe wrt. the
PAT bit: it is bit 12 on the 1GB and 2MB page table level
(_PAGE_BIT_PAT_LARGE), and it is bit 7 on the 4K page
table level (_PAGE_BIT_PAT).
Currently it is not a problem because we never set
_PAGE_BIT_PAT_LARGE on any of the large-page mappings - but
should this happen in the future the split_large_page() would
silently lift bit 12 into the lowlevel 4K pte and would start
corrupting the physical page frame offset. Not fun.
So add a debug warning, to make sure if something ever sets
the PAT bit then this function gets updated too.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix to prevent hard lockup on bad PMD permissions
If the PMD does not have the correct permissions for a page access,
but the PTE does, the spurious fault handler will mistake the fault
as a lazy TLB transaction. This will result in an infinite loop of:
fault -> spurious_fault check (pass) -> return to code -> fault
This patch adds a check and a warn on if the PTE passes the permissions
but the PMD does not.
[ Updated: Ingo Molnar suggested using WARN_ONCE with some text ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Steven Rostedt found a bug in where in his modified kernel
ftrace was unable to modify the kernel text, due to the PMD
itself having been marked read-only as well in
split_large_page().
The fix, suggested by Linus, is to not try to 'clone' the
reference protection of a huge-page, but to use the standard
(and permissive) page protection bits of KERNPG_TABLE.
The 'cloning' makes sense for the ptes but it's a confused and
incorrect concept at the page table level - because the
pagetable entry is a set of all ptes and hence cannot
'clone' any single protection attribute - the ptes can be any
mixture of protections.
With the permissive KERNPG_TABLE, even if the pte protections
get changed after this point (due to ftrace doing code-patching
or other similar activities like kprobes), the resulting combined
protections will still be correct and the pte's restrictive
(or permissive) protections will control it.
Also update the comment.
This bug was there for a long time but has not caused visible
problems before as it needs a rather large read-only area to
trigger. Steve possibly hacked his kernel with some really
large arrays or so. Anyway, the bug is definitely worth fixing.
[ Huang Ying also experienced problems in this area when writing
the EFI code, but the real bug in split_large_page() was not
realized back then. ]
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Reported-by: Huang Ying <ying.huang@intel.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: use new dynamic allocator, unified access to static/dynamic
percpu memory
Convert to the new dynamic percpu allocator.
* implement populate_extra_pte() for both 32 and 64
* update setup_per_cpu_areas() to use pcpu_setup_static()
* define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr()
* define config HAVE_DYNAMIC_PER_CPU_AREA
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: cleanup
There are two allocated per-cpu accessor macros with almost identical
spelling. The original and far more popular is per_cpu_ptr (44
files), so change over the other 4 files.
tj: kill percpu_ptr() and update UP too
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: mingo@redhat.com
Cc: lenb@kernel.org
Cc: cpufreq@vger.kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: economize memory for large NR_CPUS
percpu data is setup earlier than irq, we can use percpu data
to economize memory.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: fix time warps under vmware
Similar to the check for TSC going backwards in the TSC clocksource,
we also need this check for VMI clocksource.
Signed-off-by: Alok N Kataria <akataria@vmware.com>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: stable@kernel.org
Impact: Cleanup
The standard spelling of a printf pattern for long long is "ll", not
"L", which is for long double.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Impact: cleanup, performance enhancement
The machine check poller is diverging more and more from the fatal
exception handler. Instead of adding more special cases separate the code
paths completely. The corrected poll path is actually quite simple,
and this doesn't result in much code duplication.
This makes both handlers much easier to read and results in
cleaner code flow. The exception handler now only needs to care
about uncorrected errors, which also simplifies the handling of multiple
errors. The corrected poller also now always runs in standard interrupt
context and does not need to do anything special to handle NMI context.
Minor behaviour changes:
- MCG status is now not cleared on polling.
- Only the banks which had corrected errors get cleared on polling
- The exception handler only clears banks with errors now
v2: Forward port to new patch order. Add "uc" argument.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Impact: cleanup
This merely factors out duplicated code to set up
the initial struct mce state into a single function.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Impact: cleanup; making code future proof; memory saving on small systems
This patch replaces the hardcoded max number of machine check banks with
dynamic allocation depending on what the CPU reports. The sysfs
data structures and the banks array are dynamically allocated.
There is still a hard bank limit (128) because the mcelog protocol uses
banks >= 128 as pseudo banks to escape other events. But we expect
that 128 banks is beyond any reasonable CPU for now.
This supersedes an earlier patch by Venki, but it solves the problem
more completely by making the limit fully dynamic (up to the 128
boundary).
This saves some memory on machines with less than 6 banks because
they won't need sysdevs for unused ones and also allows to
use sysfs to control these banks on possible future CPUs with
more than 6 banks.
This is an updated patch addressing Venki's comments. I also added in
another patch from Thomas which fixed the error allocation path (that
patch was previously separated)
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Impact: Low priority fix
The 32-bit defconfig already had it enabled. And it's a pretty
fundamental feature, so better enable it on 64 bits too.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
x86, mce: fix ifdef for 64bit thermal apic vector clear on shutdown
x86, mce: use force_sig_info to kill process in machine check
x86, mce: reinitialize per cpu features on resume
x86, rcu: fix strange load average and ksoftirqd behavior
Impact: clenaup
Linker script will put startup_32 at predefined
address so using startup_32 will not bloat the
code size.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: clenaup
Linker script will put startup_32 at predefined
address so using ENTRY will not bloat the code
size.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup
We are in setup stage so we use GLOBAL
instead of ENTRY and do not increase code
size.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup
There was an attempt to bring build-time checking for
missed ENTRY_X86/END_X86 and KPROBE... pairs. Using
them will add messy in code. Get just rid of them.
This commit could be easily restored if the need appear
in future.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
If the code is time critical and this entry is called
from other places we use ENTRY to have it globally defined
and especially aligned.
Contrary we have some snippets which are size
critical. So we use plane ".globl name; name:"
directive. Introduce GLOBAL macro for this.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
What's happening is that the assertion in mm/page_alloc.c:move_freepages()
is triggering:
BUG_ON(page_zone(start_page) != page_zone(end_page));
Once I knew this is what was happening, I added some annotations:
if (unlikely(page_zone(start_page) != page_zone(end_page))) {
printk(KERN_ERR "move_freepages: Bogus zones: "
"start_page[%p] end_page[%p] zone[%p]\n",
start_page, end_page, zone);
printk(KERN_ERR "move_freepages: "
"start_zone[%p] end_zone[%p]\n",
page_zone(start_page), page_zone(end_page));
printk(KERN_ERR "move_freepages: "
"start_pfn[0x%lx] end_pfn[0x%lx]\n",
page_to_pfn(start_page), page_to_pfn(end_page));
printk(KERN_ERR "move_freepages: "
"start_nid[%d] end_nid[%d]\n",
page_to_nid(start_page), page_to_nid(end_page));
...
And here's what I got:
move_freepages: Bogus zones: start_page[2207d0000] end_page[2207dffc0] zone[fffff8103effcb00]
move_freepages: start_zone[fffff8103effcb00] end_zone[fffff8003fffeb00]
move_freepages: start_pfn[0x81f600] end_pfn[0x81f7ff]
move_freepages: start_nid[1] end_nid[0]
My memory layout on this box is:
[ 0.000000] Zone PFN ranges:
[ 0.000000] Normal 0x00000000 -> 0x0081ff5d
[ 0.000000] Movable zone start PFN for each node
[ 0.000000] early_node_map[8] active PFN ranges
[ 0.000000] 0: 0x00000000 -> 0x00020000
[ 0.000000] 1: 0x00800000 -> 0x0081f7ff
[ 0.000000] 1: 0x0081f800 -> 0x0081fe50
[ 0.000000] 1: 0x0081fed1 -> 0x0081fed8
[ 0.000000] 1: 0x0081feda -> 0x0081fedb
[ 0.000000] 1: 0x0081fedd -> 0x0081fee5
[ 0.000000] 1: 0x0081fee7 -> 0x0081ff51
[ 0.000000] 1: 0x0081ff59 -> 0x0081ff5d
So it's a block move in that 0x81f600-->0x81f7ff region which triggers
the problem.
This patch:
Declaration of early_pfn_to_nid() is scattered over per-arch include
files, and it seems it's complicated to know when the declaration is used.
I think it makes fix-for-memmap-init not easy.
This patch moves all declaration to include/linux/mm.h
After this,
if !CONFIG_NODES_POPULATES_NODE_MAP && !CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID
-> Use static definition in include/linux/mm.h
else if !CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID
-> Use generic definition in mm/page_alloc.c
else
-> per-arch back end function will be called.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reported-by: David Miller <davem@davemlloft.net>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x, 2.6.27.x, 2.6.28.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is nothing really arch specific of the push and pop functions
used by the function graph tracer. This patch moves them to generic
code.
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Intel AES-NI is a new set of Single Instruction Multiple Data (SIMD)
instructions that are going to be introduced in the next generation of
Intel processor, as of 2009. These instructions enable fast and secure
data encryption and decryption, using the Advanced Encryption Standard
(AES), defined by FIPS Publication number 197. The architecture
introduces six instructions that offer full hardware support for
AES. Four of them support high performance data encryption and
decryption, and the other two instructions support the AES key
expansion procedure.
The white paper can be downloaded from:
http://softwarecommunity.intel.com/isn/downloads/intelavx/AES-Instructions-Set_WP.pdf
AES may be used in soft_irq context, but MMX/SSE context can not be
touched safely in soft_irq context. So in_interrupt() is checked, if
in IRQ or soft_irq context, the general x86_64 implementation are used
instead.
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Intel AES-NI AES acceleration instructions touch XMM state, to use
that in soft_irq context, general x86 AES implementation is used as
fallback. The first parameter is changed from struct crypto_tfm * to
struct crypto_aes_ctx * to make it easier to deal with 16 bytes
alignment requirement of AES-NI implementation.
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The Intel AES-NI AES acceleration instructions need key_enc, key_dec
in struct crypto_aes_ctx to be 16 byte aligned, it make this easier to
move key_length to be the last one.
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Impact: bugfix
Considering the situation as follow:
before: mcelog.next == 1, mcelog.entry[0].finished = 1
+--------------------------------------------------------------------------
R W1 W2 W3
read mcelog.next (1)
mcelog.next++ (2)
(working on entry 1,
finished == 0)
mcelog.next = 0
mcelog.next++ (1)
(working on entry 0)
mcelog.next++ (2)
(working on entry 1)
<----------------- race ---------------->
(done on entry 1,
finished = 1)
(done on entry 1,
finished = 1)
To fix the race condition, a cmpxchg loop is added to mce_read() to
ensure no new MCE record can be added between mcelog.next reading and
mcelog.next = 0.
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: Lower priority bug fix
Offlined CPUs could still get machine checks, but the machine check handler
cannot handle them properly, leading to an unconditional crash. Disable
machine checks on CPUs that are going down.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: bug fix, in this case the resume handler shouldn't run which
avoids incorrectly reenabling machine checks on resume
When MCEs are completely disabled on the command line don't set
up the sysdev devices for them either.
Includes a comment fix from Thomas Gleixner.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: Higher priority bug fix
The machine check poller runs a single timer and then broadcasted an
IPI to all CPUs to check them. This leads to unnecessary
synchronization between CPUs. The original CPU running the timer has
to wait potentially a long time for all other CPUs answering. This is
also real time unfriendly and in general inefficient.
This was especially a problem on systems with a lot of events where
the poller run with a higher frequency after processing some events.
There could be more and more CPU time wasted with this, to
the point of significantly slowing down machines.
The machine check polling is actually fully independent per CPU, so
there's no reason to not just do this all with per CPU timers. This
patch implements that.
Also switch the poller also to use standard timers instead of work
queues. It was using work queues to be able to execute a user program
on a event, but mce_notify_user() handles this case now with a
separate callback. So instead always run the poll code in in a
standard per CPU timer, which means that in the common case of not
having to execute a trigger there will be less overhead.
This allows to clean up the initialization significantly, because
standard timers are already up when machine checks get init'ed. No
multiple initialization functions.
Thanks to Thomas Gleixner for some help.
Cc: thockin@google.com
v2: Use del_timer_sync() on cpu shutdown and don't try to handle
migrated timers.
v3: Add WARN_ON for timer running on unexpected CPU
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: Needed for bug fix in next patch
This relaxes the requirement that mce_notify_user has to run in process
context. Useful for future changes, but also leads to cleaner
behaviour now. Now instead mce_notify_user can be called directly
from interrupt (but not NMI) context.
The work queue only uses a single global work struct, which can be done safely
because it is always free to reuse before the trigger function is executed.
This way no events can be lost.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: low priority bug fix
This removes part of a a patch I added myself some time ago. After some
consideration the patch was a bad idea. In particular it stopped machine check
exceptions during code patching.
To quote the comment:
* MCEs only happen when something got corrupted and in this
* case we must do something about the corruption.
* Ignoring it is worse than a unlikely patching race.
* Also machine checks tend to be broadcast and if one CPU
* goes into machine check the others follow quickly, so we don't
* expect a machine check to cause undue problems during to code
* patching.
So undo the machine check related parts of
8f4e956b31 NMIs are still disabled.
This only removes code, the only additions are a new comment.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: Bug fix
During suspend it is not reliable to process machine check
exceptions, because CPUs disappear but can still get machine check
broadcasts. Also the system is slightly more likely to
machine check them, but the handler is typically not a position
to handle them in a meaningfull way.
So disable them during suspend and enable them during resume.
Also make sure they are always disabled on hot-unplugged CPUs.
This new code assumes that suspend always hotunplugs all
non BP CPUs.
v2: Remove the WARN_ONs Thomas objected to.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: Bugfix
The ifdef for the apic clear on shutdown for the 64bit intel thermal
vector was incorrect and never triggered. Fix that.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
