linux-toradex.git/arch/x86/include/asm/nmi.h, branch v3.12

x86: Fix trigger_all_cpu_backtrace() implementation

2013-06-20T12:00:21+00:00

The following change fixes the x86 implementation of
trigger_all_cpu_backtrace(), which was previously (accidentally,
as far as I can tell) disabled to always return false as on
architectures that do not implement this function.

trigger_all_cpu_backtrace(), as defined in include/linux/nmi.h,
should call arch_trigger_all_cpu_backtrace() if available, or
return false if the underlying arch doesn't implement this
function.

x86 did provide a suitable arch_trigger_all_cpu_backtrace()
implementation, but it wasn't actually being used because it was
declared in asm/nmi.h, which linux/nmi.h doesn't include. Also,
linux/nmi.h couldn't easily be fixed by including asm/nmi.h,
because that file is not available on all architectures.

I am proposing to fix this by moving the x86 definition of
arch_trigger_all_cpu_backtrace() to asm/irq.h.

Tested via: echo l > /proc/sysrq-trigger

Before the change, this uses a fallback implementation which
shows backtraces on active CPUs (using
smp_call_function_interrupt() )

After the change, this shows NMI backtraces on all CPUs

Signed-off-by: Michel Lespinasse 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1370518875-1346-1-git-send-email-walken@google.com
Signed-off-by: Ingo Molnar

x86/nmi: Clean up register_nmi_handler() usage

2012-06-20T12:23:17+00:00

Implement a cleaner and easier to maintain version for the section
warning fixes implemented in commit eeaaa96a3a21
("x86/nmi: Fix section mismatch warnings on 32-bit").

Signed-off-by: Li Zhong 
Signed-off-by: Don Zickus 
Cc: Jan Beulich 
Link: http://lkml.kernel.org/r/1340049393-17771-1-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86/nmi: Fix section mismatch warnings on 32-bit

2012-06-08T10:19:27+00:00

It was reported that compiling for 32-bit caused a bunch of
section mismatch warnings:

 VDSOSYM arch/x86/vdso/vdso32-syms.lds
  LD      arch/x86/vdso/built-in.o
  LD      arch/x86/built-in.o

 WARNING: arch/x86/built-in.o(.data+0x5af0): Section mismatch in
 reference from the variable test_nmi_ipi_callback_na.10451 to
 the function .init.text:test_nmi_ipi_callback() [...]

 WARNING: arch/x86/built-in.o(.data+0x5b04): Section mismatch in
 reference from the variable nmi_unk_cb_na.10399 to the function
 .init.text:nmi_unk_cb() The variable nmi_unk_cb_na.10399
 references the function __init nmi_unk_cb() [...]

Both of these are attributed to the internal representation of
the nmiaction struct created during register_nmi_handler.  The
reason for this is that those structs are not defined in the
init section whereas the rest of the code in nmi_selftest.c is.

To resolve this, I created a new #define,
register_nmi_handler_initonly, that tags the struct as
__initdata to resolve the mismatch.  This #define should only be
used in rare situations where the register/unregister is called
during init of the kernel.

Big thanks to Jan Beulich for decoding this for me as I didn't
have a clue what was going on.

Reported-by: Witold Baryluk 
Tested-by: Witold Baryluk 
Cc: Jan Beulich 
Signed-off-by: Don Zickus 
Link: http://lkml.kernel.org/r/1338991542-23000-1-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86/nmi: Fix the type of the nmiaction.flags field

2012-05-07T10:32:11+00:00

This patch changes the type of the struct nmiaction flags field
to unsigned long from unsigned int. All the usages of the flags
field are unsigned long already. There is only one flag used
currently, NMI_FLAG_FIRST, but having the wrong size could cause
a truncation bug in the future on 64 bit architectures.

Signed-off-by: Betty Dall 
Acked-by: Don Zickus 
Link: http://lkml.kernel.org/r/1335559255-13454-1-git-send-email-betty.dall@hp.com
Signed-off-by: Ingo Molnar

x86/nmi: Fix page faults by nmiaction if kmemcheck is enabled

2012-04-25T10:44:06+00:00

This patch tries to fix the problem of page fault exception
caused by accessing nmiaction structure in nmi if kmemcheck
is enabled.

If kmemcheck is enabled, the memory allocated through slab are
in pages that are marked non-present, so that some checks could
be done in the page fault handling code ( e.g. whether the
memory is read before written to ).

As nmiaction is allocated in this way, so it resides in a
non-present page. Then there is a page fault while the nmi code
accessing the nmiaction structure, which would then cause a
warning by WARN_ON_ONCE(in_nmi()) in kmemcheck_fault(), called
by do_page_fault().

This significantly simplifies the code as well, as the whole
dynamic allocation dance goes away.

v2: as Peter suggested, changed the nmiaction to use static
    storage.

v3: as Peter suggested, use macro to shorten the codes. Also
    keep the original usage of register_nmi_handler, so users of
    this call doesn't need change.

Tested-by: Seiji Aguchi 
Fixes: https://lkml.org/lkml/2012/3/2/356
Signed-off-by: Li Zhong 
[ simplified the wrappers ]
Signed-off-by: Don Zickus 
Cc: Peter Zijlstra 
Cc: thomas.mingarelli@hp.com
Cc: Linus Torvalds 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/1333051877-15755-4-git-send-email-dzickus@redhat.com
[ tidied the patch a bit ]
Signed-off-by: Ingo Molnar

x86/nmi: Add new NMI queues to deal with IO_CHK and SERR

2012-04-25T10:43:34+00:00

In discussions with Thomas Mingarelli about hpwdt, he explained
to me some issues they were some when using their virtual NMI
button to test the hpwdt driver.

It turns out the virtual NMI button used on HP's machines do no
send unknown NMIs but instead send IO_CHK NMIs.  The way the
kernel code is written, the hpwdt driver can not register itself
against that type of NMI and therefore can not successfully
capture system information before panic'ing.

To solve this I created two new NMI queues to allow driver to
register against the IO_CHK and SERR NMIs.  Or in the hpwdt all
three (if you include unknown NMIs too).

The change is straightforward and just mimics what the unknown
NMI does.

Reported-and-tested-by: Thomas Mingarelli 
Signed-off-by: Don Zickus 
Cc: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/1333051877-15755-3-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86, nmi: Add in logic to handle multiple events and unknown NMIs

2011-10-10T04:57:01+00:00

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: Don Zickus 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1317409584-23662-5-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86, nmi: Wire up NMI handlers to new routines

2011-10-10T04:56:57+00:00

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: Don Zickus 
Signed-off-by: Peter Zijlstra 
Acked-by: Corey Minyard 
Cc: Jason Wessel 
Cc: Andi Kleen 
Cc: Robert Richter 
Cc: Huang Ying 
Cc: Corey Minyard 
Cc: Jack Steiner 
Link: http://lkml.kernel.org/r/1317409584-23662-4-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86, nmi: Create new NMI handler routines

2011-10-10T04:56:52+00:00

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: Don Zickus 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1317409584-23662-3-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86: Fix common misspellings

2011-03-18T09:39:30+00:00

They were generated by 'codespell' and then manually reviewed.

Signed-off-by: Lucas De Marchi 
Cc: trivial@kernel.org
LKML-Reference: <1300389856-1099-3-git-send-email-lucas.demarchi@profusion.mobi>
Signed-off-by: Ingo Molnar