With i386, NMIs and breakpoints use the current stack and they
do not reset the stack pointer to a fix point that might corrupt
a previous NMI or breakpoint (as it does in x86_64). But NMIs are
still not made to be re-entrant, and need to prevent the case that
an NMI hitting a breakpoint (which does an iret), doesn't allow
another NMI to run.

The fix is to let the NMI be in 3 different states:

1) not running
2) executing
3) latched

When no NMI is executing on a given CPU, the state is "not running".
When the first NMI comes in, the state is switched to "executing".
On exit of that NMI, a cmpxchg is performed to switch the state
back to "not running" and if that fails, the NMI is restarted.

If a breakpoint is hit and does an iret, which re-enables NMIs,
and another NMI comes in before the first NMI finished, it will
detect that the state is not in the "not running" state and the
current NMI is nested. In this case, the state is switched to "latched"
to let the interrupted NMI know to restart the NMI handler, and
the nested NMI exits without doing anything.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Turner <pjt@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

We want to allow NMI handlers to have breakpoints to be able to
remove stop_machine from ftrace, kprobes and jump_labels. But if
an NMI interrupts a current breakpoint, and then it triggers a
breakpoint itself, it will switch to the breakpoint stack and
corrupt the data on it for the breakpoint processing that it
interrupted.

Instead, have the NMI check if it interrupted breakpoint processing
by checking if the stack that is currently used is a breakpoint
stack. If it is, then load a special IDT that changes the IST
for the debug exception to keep the same stack in kernel context.
When the NMI is done, it puts it back.

This way, if the NMI does trigger a breakpoint, it will keep
using the same stack and not stomp on the breakpoint data for
the breakpoint it interrupted.
Suggested-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

with "apic=verbose" the print_IO_APIC() function tries to print
IRQ to pin mappings for every active irq. It assumes chip_data
is of type irq_cfg and may cause an oops if not.

As the print_IO_APIC() is called from a late_initcall other
chained irq chips may already be registered with custom
chip_data information, causing an oops. This is the case with
intel MID SoC devices with gpio demuxers registered as irq_chips.
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
[ -v2: fixed build failure ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Moorestown/Medfield platform does not have port 0x61 to report
NMI status, nor does it have external NMI sources. The only NMI
sources are from lapic, as results of perf counter overflow or
IPI, e.g. NMI watchdog or spin lock debug.

Reading port 0x61 on Moorestown will return 0xff which misled
NMI handlers to false critical errors such memory parity error.
The subsequent ioport access for NMI handling can also cause
undefined behavior on Moorestown.

This patch allows kernel process NMI due to watchdog or backrace
dump without unnecessary hangs.
Signed-off-by: NJacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
[hand applied]
Signed-off-by: NAlan Cox <alan@linux.intel.com>

These files were implicitly getting EXPORT_SYMBOL via device.h
which was including module.h, but that will be fixed up shortly.

By fixing these now, we can avoid seeing things like:

arch/x86/kernel/rtc.c:29: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’
arch/x86/kernel/pci-dma.c:20: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’
arch/x86/kernel/e820.c:69: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL_GPL’

[ with input from Randy Dunlap <rdunlap@xenotime.net> and also
  from Stephen Rothwell <sfr@canb.auug.org.au> ]
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

nmi.c needs an #include <linux/mca.h>:

 arch/x86/kernel/nmi.c: In function ‘unknown_nmi_error’:
 arch/x86/kernel/nmi.c:286:6: error: ‘MCA_bus’ undeclared (first use in this function)
 arch/x86/kernel/nmi.c:286:6: note: each undeclared identifier is reported only once for each function it appears in

Another one is the hpwdt driver:

 drivers/watchdog/hpwdt.c:507:9: error: ‘NMI_DONE’ undeclared (first use in this function)
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Now that the NMI handler are broken into lists, increment the appropriate
stats for each list.  This allows us to see what is going on when they
get printed out in the next patch.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1317409584-23662-6-git-send-email-dzickus@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Previous patches allow the NMI subsystem to process multipe NMI events
in one NMI.  As previously discussed this can cause issues when an event
triggered another NMI but is processed in the current NMI.  This causes the
next NMI to go unprocessed and become an 'unknown' NMI.

To handle this, we first have to flag whether or not the NMI handler handled
more than one event or not.  If it did, then there exists a chance that
the next NMI might be already processed.  Once the NMI is flagged as a
candidate to be swallowed, we next look for a back-to-back NMI condition.

This is determined by looking at the %rip from pt_regs.  If it is the same
as the previous NMI, it is assumed the cpu did not have a chance to jump
back into a non-NMI context and execute code and instead handled another NMI.

If both of those conditions are true then we will swallow any unknown NMI.

There still exists a chance that we accidentally swallow a real unknown NMI,
but for now things seem better.

An optimization has also been added to the nmi notifier rountine.  Because x86
can latch up to one NMI while currently processing an NMI, we don't have to
worry about executing _all_ the handlers in a standalone NMI.  The idea is
if multiple NMIs come in, the second NMI will represent them.  For those
back-to-back NMI cases, we have the potentail to drop NMIs.  Therefore only
execute all the handlers in the second half of a detected back-to-back NMI.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1317409584-23662-5-git-send-email-dzickus@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Just convert all the files that have an nmi handler to the new routines.
Most of it is straight forward conversion.  A couple of places needed some
tweaking like kgdb which separates the debug notifier from the nmi handler
and mce removes a call to notify_die.

[Thanks to Ying for finding out the history behind that mce call

https://lkml.org/lkml/2010/5/27/114

And Boris responding that he would like to remove that call because of it

https://lkml.org/lkml/2011/9/21/163]

The things that get converted are the registeration/unregistration routines
and the nmi handler itself has its args changed along with code removal
to check which list it is on (most are on one NMI list except for kgdb
which has both an NMI routine and an NMI Unknown routine).
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NCorey Minyard <minyard@acm.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Corey Minyard <minyard@acm.org>
Cc: Jack Steiner <steiner@sgi.com>
Link: http://lkml.kernel.org/r/1317409584-23662-4-git-send-email-dzickus@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

The NMI handlers used to rely on the notifier infrastructure.  This worked
great until we wanted to support handling multiple events better.

One of the key ideas to the nmi handling is to process _all_ the handlers for
each NMI.  The reason behind this switch is because NMIs are edge triggered.
If enough NMIs are triggered, then they could be lost because the cpu can
only latch at most one NMI (besides the one currently being processed).

In order to deal with this we have decided to process all the NMI handlers
for each NMI.  This allows the handlers to determine if they recieved an
event or not (the ones that can not determine this will be left to fend
for themselves on the unknown NMI list).

As a result of this change it is now possible to have an extra NMI that
was destined to be received for an already processed event.  Because the
event was processed in the previous NMI, this NMI gets dropped and becomes
an 'unknown' NMI.  This of course will cause printks that scare people.

However, we prefer to have extra NMIs as opposed to losing NMIs and as such
are have developed a basic mechanism to catch most of them.  That will be
a later patch.

To accomplish this idea, I unhooked the nmi handlers from the notifier
routines and created a new mechanism loosely based on doIRQ.  The reason
for this is the notifier routines have a couple of shortcomings.  One we
could't guarantee all future NMI handlers used NOTIFY_OK instead of
NOTIFY_STOP.  Second, we couldn't keep track of the number of events being
handled in each routine (most only handle one, perf can handle more than one).
Third, I wanted to eventually display which nmi handlers are registered in
the system in /proc/interrupts to help see who is generating NMIs.

The patch below just implements the new infrastructure but doesn't wire it up
yet (that is the next patch).  Its design is based on doIRQ structs and the
atomic notifier routines.  So the rcu stuff in the patch isn't entirely untested
(as the notifier routines have soaked it) but it should be double checked in
case I copied the code wrong.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1317409584-23662-3-git-send-email-dzickus@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

The nmi stuff is changing a lot and adding more functionality.  Split it
out from the traps.c file so it doesn't continue to pollute that file.

This makes it easier to find and expand all the future nmi related work.

No real functional changes here.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1317409584-23662-2-git-send-email-dzickus@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/ is getting a bit crowded, and the APIC
drivers are scattered into various different files.

Move them to arch/x86/kernel/apic/*, and also remove
the 'gen' prefix from those which had it.

Also move APIC related functionality: the IO-APIC driver,
the NMI and the IPI code.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

Remove genapic.h and remove all references to it.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

make it simpler, don't need have one extra struct.

v2: fix the sgi_uv build
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

We are getting rid of subarchitecture support - move the hook files
to asm/. (These are now stale and should be replaced with more explicit
runtime mechanisms - but the transition is simpler this way.)
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NBrian Gerst <brgerst@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

Removed duplicated #include's in:

  arch/x86/kernel/mpparse.c
  arch/x86/kernel/nmi.c
Signed-off-by: NHuang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup, fix style problems

Fixes style problems:

 WARNING: Use #include <linux/smp.h> instead of <asm/smp.h>
 WARNING: Use #include <linux/nmi.h> instead of <asm/nmi.h>

total: 0 errors, 2 warnings
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: introduce nmi_watchdog=lapic and nmi_watchdog=ioapic aliases

Add sensible names as "lapic" and "ioapic" to
nmi_watchdog boot parameter. Sometimes it is not
that easy to recall what exactly nmi_watchdog=1
does mean so we allow the using of symbolic names here.

Old numeric values remain valid.
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: change NMI watchdog detection and disabling sequence

Currently, if the NMI watchdog fails using IOAPIC method, it'll only disable
interrupts on 8259 if the timer is passing thru it. This patch disables
NMI delivery on LINT0 if the NMI watchdog initial test fails, just for safety.
Signed-off-by: NAristeu Rozanski <aris@redhat.com>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: change/improve the way /proc/sys/kernel/nmi_watchdog works

This patch adds support to enable/disable IOAPIC NMI watchdog in runtime via
procfs.
Signed-off-by: NAristeu Rozanski <aris@redhat.com>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

There's a small window when NMI watchdog is being set up that if any NMIs
are triggered, the NMI code will make make use of not initalized wd_ops
elements:
	void setup_apic_nmi_watchdog(void *unused)
	{
		if (__get_cpu_var(wd_enabled))
			return;

		/* cheap hack to support suspend/resume */
		/* if cpu0 is not active neither should the other cpus */
		if (smp_processor_id() != 0 && atomic_read(&nmi_active) <= 0)
			return;

		switch (nmi_watchdog) {
		case NMI_LOCAL_APIC:
			/* enable it before to avoid race with handler */
-->			__get_cpu_var(wd_enabled) = 1;
-->			if (lapic_watchdog_init(nmi_hz) < 0) {
(...)
	asmlinkage notrace __kprobes void default_do_nmi(struct pt_regs *regs)
	{
	(...)
			if (nmi_watchdog_tick(regs, reason))
				return;
(...)
	notrace __kprobes int
	nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
	{
	(...)
		if (!__get_cpu_var(wd_enabled))
			return rc;
		switch (nmi_watchdog) {
		case NMI_LOCAL_APIC:
			rc |= lapic_wd_event(nmi_hz);
(...)
int lapic_wd_event(unsigned nmi_hz)
{
	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
	u64 ctr;

-->	rdmsrl(wd->perfctr_msr, ctr);

and wd->*_msr will be initialized on each processor type specific setup, after
enabling NMIs for PMIs. Since the counter was just set, the chances of an
performance counter generated NMI is minimal, but any other unknown NMI would
trigger the problem. This patch fixes the problem by setting everything up
before enabling performance counter generated NMIs and will set wd_enabled
using a callback function.
Signed-off-by: NAristeu Rozanski <aris@redhat.com>
Acked-by: NDon Zickus <dzickus@redhat.com>
Acked-by: NPrarit Bhargava <prarit@redhat.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

clean up the failure message - and redirect people to bugzilla
instead of lkml.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

> it just won't work at boot time - the second logic unit will be stuck:
>
> Booting processor 1/2 APIC 0x1
> Initializing CPU#1
> Calibrating delay using timer specific routine.. 5586.12 BogoMIPS (lpj=2793063)
> CPU: Trace cache: 12K uops, L1 D cache: 16K
> CPU: L2 cache: 1024K
> CPU: Physical Processor ID: 0
> CPU: Processor Core ID: 1
> CPU1: Thermal monitoring enabled (TM1)
>               Intel(R) Pentium(R) D CPU 2.80GHz stepping 04
> Brought up 2 CPUs
> testing NMI watchdog ... <4>WARNING: CPU#1: NMI appears to be stuck (0->0)!

while at it... - fix that newline
Signed-off-by: NAristeu Rozanski <aris@redhat.com>
Cc: jvillalo@redhat.com
Signed-off-by: NIngo Molnar <mingo@elte.hu>

It's not possible to enable the unknown_nmi_panic sysctl option
until init is run. It's useful to be able to panic the kernel
during boot too, this adds a parameter to enable this option.
Signed-off-by: NSimon Arlott <simon@fire.lp0.eu>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Use alternatives to select the workaround for the 11AP Pentium erratum
for the affected steppings on the fly rather than build time.  Remove the
X86_GOOD_APIC configuration option and replace all the calls to
apic_write_around() with plain apic_write(), protecting accesses to the
ESR as appropriate due to the 3AP Pentium erratum.  Remove
apic_read_around() and all its invocations altogether as not needed.
Remove apic_write_atomic() and all its implementing backends.  The use of
ASM_OUTPUT2() is not strictly needed for input constraints, but I have
used it for readability's sake.

I had the feeling no one else was brave enough to do it, so I went ahead
and here it is.  Verified by checking the generated assembly and tested
with both a 32-bit and a 64-bit configuration, also with the 11AP
"feature" forced on and verified with gdb on /proc/kcore to work as
expected (as an 11AP machines are quite hard to get hands on these days).
Some script complained about the use of "volatile", but apic_write() needs
it for the same reason and is effectively a replacement for writel(), so I
have disregarded it.

I am not sure what the policy wrt defconfig files is, they are generated
and there is risk of a conflict resulting from an unrelated change, so I
have left changes to them out.  The option will get removed from them at
the next run.

Some testing with machines other than mine will be needed to avoid some
stupid mistake, but despite its volume, the change is not really that
intrusive, so I am fairly confident that because it works for me, it will
everywhere.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

In the course of the recent unification of the NMI watchdog an assignment
to timer_ack to switch off unnecesary POLL commands to the 8259A in the
case of a watchdog failure has been accidentally removed.  The statement
used to be limited to the 32-bit variation as since the rewrite of the
timer code it has been relevant for the 82489DX only.  This change brings
it back.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: macro@linux-mips.org
Signed-off-by: NIngo Molnar <mingo@elte.hu>

There is no need to keep NMI_DISABLED definition and use it
for nmi_watchdog by default. Here is the point why:

- IO-APIC and APIC chips are programmed for nmi_watchdog support at very
  early stage of kernel booting and not having nmi_watchdog specified as
  boot option lead only to nmi_watchdog becomes to NMI_NONE anyway
- enable nmi_watchdog thru /proc/sys/kernel/nmi if it was not specified at
  boot is not possible too (even having this sysfs entry)
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: macro@linux-mips.org
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Since nmi_watchdog is unsigned variable we may
safely remove the check for negative value.
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: macro@linux-mips.org
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NIngo Molnar <mingo@elte.hu>

The checking 'if nmi_watchdog > 0' (ie NMI_NONE) is quite fast but it
has a side effect - it's taken even if nmi_watchdog = NMI_DISABLED.

Nowadays nmi_watchdog is set up to NMI_NONE by default so this condition
is properly taken most the time but we better show this explicitly.
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

fix:

arch/x86/kernel/built-in.o: In function `proc_nmi_enabled':
: undefined reference to `nmi_watchdog_default'
arch/x86/kernel/built-in.o: In function `native_smp_prepare_cpus':
: undefined reference to `nmi_watchdog_default'
Signed-off-by: NIngo Molnar <mingo@elte.hu>

64bit mode bootstrap code does set nmi_watchdog to NMI_NONE
by default and doing the same on 32bit mode is safe too.
Such an action saves us from several #ifdef.

Btw, my previous commit

commit 19ec673c
Author: Cyrill Gorcunov <gorcunov@gmail.com>
Date:   Wed May 28 23:00:47 2008 +0400

    x86: nmi - fix incorrect NMI watchdog used by default

did not fix the problem completely, moreover it
introduced additional bug - nmi_watchdog would be
set to either NMI_LOCAL_APIC or NMI_IO_APIC
_regardless_ to boot option if being enabled thru
/proc/sys/kernel/nmi_watchdog. Sorry for that.
Fix it too.
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: macro@linux-mips.org
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

apic.h needs to be included for the apic_write_around() definition.

before
	total: 1 errors, 6 warnings, 534 lines checked
after
	total: 0 errors, 1 warnings, 532 lines checked
Signed-off-by: NHiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The commit

	commit 4b82b277
	Author: Cyrill Gorcunov <gorcunov@gmail.com>
	Date:   Sat May 24 19:36:35 2008 +0400

set nmi_watchdog to NMI_IO_APIC as by default. This causes hangs on some
machines with buggy watchdogs. Fix it - i.e. restore old behaviour.

Thanks to Sitsofe Wheeler and Adrian Bunk for catching the problem
and Maciej W. Rozycki for explanation what is going on there.
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
CC: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: hpa@zytor.com
Cc: mingo@redhat.com
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: hpa@zytor.com
Cc: mingo@redhat.com
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Since cpu_online_map is touched (by for_each_online_cpu)
at moment when cpu_callin_map is already filled up we can
get rid of its checking at all
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: hpa@zytor.com
Cc: mingo@redhat.com
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>