linux-stable.git/arch/arm/kernel/smp.c, branch linux-4.9.y

ARM: prevent tracing IPI_CPU_BACKTRACE

2019-06-22T06:17:12+00:00

[ Upstream commit be167862ae7dd85c56d385209a4890678e1b0488 ]

Patch series "compiler: allow all arches to enable
CONFIG_OPTIMIZE_INLINING", v3.

This patch (of 11):

When function tracing for IPIs is enabled, we get a warning for an
overflow of the ipi_types array with the IPI_CPU_BACKTRACE type as
triggered by raise_nmi():

  arch/arm/kernel/smp.c: In function 'raise_nmi':
  arch/arm/kernel/smp.c:489:2: error: array subscript is above array bounds [-Werror=array-bounds]
    trace_ipi_raise(target, ipi_types[ipinr]);

This is a correct warning as we actually overflow the array here.

This patch raise_nmi() to call __smp_cross_call() instead of
smp_cross_call(), to avoid calling into ftrace.  For clarification, I'm
also adding a two new code comments describing how this one is special.

The warning appears to have shown up after commit e7273ff49acf ("ARM:
8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI"), which changed the
number assignment from '15' to '8', but as far as I can tell has existed
since the IPI tracepoints were first introduced.  If we decide to
backport this patch to stable kernels, we probably need to backport
e7273ff49acf as well.

[yamada.masahiro@socionext.com: rebase on v5.1-rc1]
Link: http://lkml.kernel.org/r/20190423034959.13525-2-yamada.masahiro@socionext.com
Fixes: e7273ff49acf ("ARM: 8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI")
Fixes: 365ec7b17327 ("ARM: add IPI tracepoints") # v3.17
Signed-off-by: Arnd Bergmann 
Signed-off-by: Masahiro Yamada 
Cc: Heiko Carstens 
Cc: Arnd Bergmann 
Cc: Ingo Molnar 
Cc: Christophe Leroy 
Cc: Mathieu Malaterre 
Cc: "H. Peter Anvin" 
Cc: Thomas Gleixner 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Ralf Baechle 
Cc: Stefan Agner 
Cc: Boris Brezillon 
Cc: Miquel Raynal 
Cc: Richard Weinberger 
Cc: David Woodhouse 
Cc: Brian Norris 
Cc: Marek Vasut 
Cc: Russell King 
Cc: Borislav Petkov 
Cc: Mark Rutland 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

ARM: avoid Cortex-A9 livelock on tight dmb loops

2019-04-05T20:29:13+00:00

[ Upstream commit 5388a5b82199facacd3d7ac0d05aca6e8f902fed ]

machine_crash_nonpanic_core() does this:

	while (1)
		cpu_relax();

because the kernel has crashed, and we have no known safe way to deal
with the CPU.  So, we place the CPU into an infinite loop which we
expect it to never exit - at least not until the system as a whole is
reset by some method.

In the absence of erratum 754327, this code assembles to:

	b	.

In other words, an infinite loop.  When erratum 754327 is enabled,
this becomes:

1:	dmb
	b	1b

It has been observed that on some systems (eg, OMAP4) where, if a
crash is triggered, the system tries to kexec into the panic kernel,
but fails after taking the secondary CPU down - placing it into one
of these loops.  This causes the system to livelock, and the most
noticable effect is the system stops after issuing:

	Loading crashdump kernel...

to the system console.

The tested as working solution I came up with was to add wfe() to
these infinite loops thusly:

	while (1) {
		cpu_relax();
		wfe();
	}

which, without 754327 builds to:

1:	wfe
	b	1b

or with 754327 is enabled:

1:	dmb
	wfe
	b	1b

Adding "wfe" does two things depending on the environment we're running
under:
- where we're running on bare metal, and the processor implements
  "wfe", it stops us spinning endlessly in a loop where we're never
  going to do any useful work.
- if we're running in a VM, it allows the CPU to be given back to the
  hypervisor and rescheduled for other purposes (maybe a different VM)
  rather than wasting CPU cycles inside a crashed VM.

However, in light of erratum 794072, Will Deacon wanted to see 10 nops
as well - which is reasonable to cover the case where we have erratum
754327 enabled _and_ we have a processor that doesn't implement the
wfe hint.

So, we now end up with:

1:      wfe
        b       1b

when erratum 754327 is disabled, or:

1:      dmb
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        wfe
        b       1b

when erratum 754327 is enabled.  We also get the dmb + 10 nop
sequence elsewhere in the kernel, in terminating loops.

This is reasonable - it means we get the workaround for erratum
794072 when erratum 754327 is enabled, but still relinquish the dead
processor - either by placing it in a lower power mode when wfe is
implemented as such or by returning it to the hypervisior, or in the
case where wfe is a no-op, we use the workaround specified in erratum
794072 to avoid the problem.

These as two entirely orthogonal problems - the 10 nops addresses
erratum 794072, and the wfe is an optimisation that makes the system
more efficient when crashed either in terms of power consumption or
by allowing the host/other VMs to make use of the CPU.

I don't see any reason not to use kexec() inside a VM - it has the
potential to provide automated recovery from a failure of the VMs
kernel with the opportunity for saving a crashdump of the failure.
A panic() with a reboot timeout won't do that, and reading the
libvirt documentation, setting on_reboot to "preserve" won't either
(the documentation states "The preserve action for an on_reboot event
is treated as a destroy".)  Surely it has to be a good thing to
avoiding having CPUs spinning inside a VM that is doing no useful
work.

Acked-by: Will Deacon 
Signed-off-by: Russell King 
Signed-off-by: Sasha Levin

ARM: 8824/1: fix a migrating irq bug when hotplug cpu

2019-03-23T12:19:42+00:00

[ Upstream commit 1b5ba350784242eb1f899bcffd95d2c7cff61e84 ]

Arm TC2 fails cpu hotplug stress test.

This issue was tracked down to a missing copy of the new affinity
cpumask for the vexpress-spc interrupt into struct
irq_common_data.affinity when the interrupt is migrated in
migrate_one_irq().

Fix it by replacing the arm specific hotplug cpu migration with the
generic irq code.

This is the counterpart implementation to commit 217d453d473c ("arm64:
fix a migrating irq bug when hotplug cpu").

Tested with cpu hotplug stress test on Arm TC2 (multi_v7_defconfig plus
CONFIG_ARM_BIG_LITTLE_CPUFREQ=y and CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y).
The vexpress-spc interrupt (irq=22) on this board is affine to CPU0.
Its affinity cpumask now changes correctly e.g. from 0 to 1-4 when
CPU0 is hotplugged out.

Suggested-by: Marc Zyngier 
Signed-off-by: Dietmar Eggemann 
Acked-by: Marc Zyngier 
Reviewed-by: Linus Walleij 
Signed-off-by: Russell King 
Signed-off-by: Sasha Levin

ARM: spectre-v2: per-CPU vtables to work around big.Little systems

2019-02-20T09:18:27+00:00

Commit 383fb3ee8024d596f488d2dbaf45e572897acbdb upstream.

In big.Little systems, some CPUs require the Spectre workarounds in
paths such as the context switch, but other CPUs do not.  In order
to handle these differences, we need per-CPU vtables.

We are unable to use the kernel's per-CPU variables to support this
as per-CPU is not initialised at times when we need access to the
vtables, so we have to use an array indexed by logical CPU number.

We use an array-of-pointers to avoid having function pointers in
the kernel's read/write .data section.

Note: Added include of linux/slab.h in arch/arm/smp.c.

Reviewed-by: Julien Thierry 
Signed-off-by: Russell King 
Signed-off-by: David A. Long 
Reviewed-by: Julien Thierry 
Signed-off-by: Sasha Levin

ARM: 8808/1: kexec:offline panic_smp_self_stop CPU

2019-02-12T18:44:51+00:00

[ Upstream commit 82c08c3e7f171aa7f579b231d0abbc1d62e91974 ]

In case panic() and panic() called at the same time on different CPUS.
For example:
CPU 0:
  panic()
     __crash_kexec
       machine_crash_shutdown
         crash_smp_send_stop
       machine_kexec
         BUG_ON(num_online_cpus() > 1);

CPU 1:
  panic()
    local_irq_disable
    panic_smp_self_stop

If CPU 1 calls panic_smp_self_stop() before crash_smp_send_stop(), kdump
fails. CPU1 can't receive the ipi irq, CPU1 will be always online.
To fix this problem, this patch split out the panic_smp_self_stop()
and add set_cpu_online(smp_processor_id(), false).

Signed-off-by: Yufen Wang 
Signed-off-by: Russell King 
Signed-off-by: Sasha Levin

ARM: bugs: hook processor bug checking into SMP and suspend paths

2018-11-23T07:20:37+00:00

Commit 26602161b5ba795928a5a719fe1d5d9f2ab5c3ef upstream.

Check for CPU bugs when secondary processors are being brought online,
and also when CPUs are resuming from a low power mode.  This gives an
opportunity to check that processor specific bug workarounds are
correctly enabled for all paths that a CPU re-enters the kernel.

Signed-off-by: Russell King 
Reviewed-by: Florian Fainelli 
Boot-tested-by: Tony Lindgren 
Reviewed-by: Tony Lindgren 
Acked-by: Marc Zyngier 
Signed-off-by: David A. Long 
Signed-off-by: Greg Kroah-Hartman

nmi_backtrace: do a local dump_stack() instead of a self-NMI

2016-10-08T01:46:30+00:00

Currently on arm there is code that checks whether it should call
dump_stack() explicitly, to avoid trying to raise an NMI when the
current context is not preemptible by the backtrace IPI.  Similarly, the
forthcoming arch/tile support uses an IPI mechanism that does not
support generating an NMI to self.

Accordingly, move the code that guards this case into the generic
mechanism, and invoke it unconditionally whenever we want a backtrace of
the current cpu.  It seems plausible that in all cases, dump_stack()
will generate better information than generating a stack from the NMI
handler.  The register state will be missing, but that state is likely
not particularly helpful in any case.

Or, if we think it is helpful, we should be capturing and emitting the
current register state in all cases when regs == NULL is passed to
nmi_cpu_backtrace().

Link: http://lkml.kernel.org/r/1472487169-14923-3-git-send-email-cmetcalf@mellanox.com
Signed-off-by: Chris Metcalf 
Tested-by: Daniel Thompson  [arm]
Reviewed-by: Petr Mladek 
Acked-by: Aaron Tomlin 
Cc: "Rafael J. Wysocki" 
Cc: Russell King 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nmi_backtrace: add more trigger_*_cpu_backtrace() methods

2016-10-08T01:46:30+00:00

Patch series "improvements to the nmi_backtrace code" v9.

This patch series modifies the trigger_xxx_backtrace() NMI-based remote
backtracing code to make it more flexible, and makes a few small
improvements along the way.

The motivation comes from the task isolation code, where there are
scenarios where we want to be able to diagnose a case where some cpu is
about to interrupt a task-isolated cpu.  It can be helpful to see both
where the interrupting cpu is, and also an approximation of where the
cpu that is being interrupted is.  The nmi_backtrace framework allows us
to discover the stack of the interrupted cpu.

I've tested that the change works as desired on tile, and build-tested
x86, arm, mips, and sparc64.  For x86 I confirmed that the generic
cpuidle stuff as well as the architecture-specific routines are in the
new cpuidle section.  For arm, mips, and sparc I just build-tested it
and made sure the generic cpuidle routines were in the new cpuidle
section, but I didn't attempt to figure out which the platform-specific
idle routines might be.  That might be more usefully done by someone
with platform experience in follow-up patches.

This patch (of 4):

Currently you can only request a backtrace of either all cpus, or all
cpus but yourself.  It can also be helpful to request a remote backtrace
of a single cpu, and since we want that, the logical extension is to
support a cpumask as the underlying primitive.

This change modifies the existing lib/nmi_backtrace.c code to take a
cpumask as its basic primitive, and modifies the linux/nmi.h code to use
the new "cpumask" method instead.

The existing clients of nmi_backtrace (arm and x86) are converted to
using the new cpumask approach in this change.

The other users of the backtracing API (sparc64 and mips) are converted
to use the cpumask approach rather than the all/allbutself approach.
The mips code ignored the "include_self" boolean but with this change it
will now also dump a local backtrace if requested.

Link: http://lkml.kernel.org/r/1472487169-14923-2-git-send-email-cmetcalf@mellanox.com
Signed-off-by: Chris Metcalf 
Tested-by: Daniel Thompson  [arm]
Reviewed-by: Aaron Tomlin 
Reviewed-by: Petr Mladek 
Cc: "Rafael J. Wysocki" 
Cc: Russell King 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Ralf Baechle 
Cc: David Miller 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ARM: 8595/2: apply more __ro_after_init

2016-08-12T15:47:06+00:00

Guided by grsecurity's analogous __read_only markings in arch/arm,
this applies several uses of __ro_after_init to structures that are
only updated during __init.

Signed-off-by: Kees Cook 
Signed-off-by: Russell King

Merge tag 'fixes-rcu-fiq-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into fixes

2016-06-19T05:21:52+00:00

Fixes for omaps for v4.7-rc cycle:

- Two boot warning fixes from the RCU tree that should have gotten
  merged several weeks ago already but did not because of issues
  with who merges them. Paul has now split the RCU warning fixes into
  sets for various maintainers.

- Fix ams-delta FIQ regression caused by omap1 sparse IRQ changes

- Fix PM for omap3 boards using timer12 and gptimer, like the
  original beagleboard

- Fix hangs on am437x-sk-evm by lowering the I2C bus speed

* tag 'fixes-rcu-fiq-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  ARM: dts: am437x-sk-evm: Reduce i2c0 bus speed for tps65218
  ARM: OMAP2+: timer: add probe for clocksources
  ARM: OMAP1: fix ams-delta FIQ handler to work with sparse IRQ
  arm: Use _rcuidle for smp_cross_call() tracepoints
  arm: Use _rcuidle tracepoint to allow use from idle

Signed-off-by: Olof Johansson