linux.git/arch/powerpc/kernel, branch v4.13

powerpc: Fix VSX enabling/flushing to also test MSR_FP and MSR_VEC

2017-08-16T09:35:54+00:00

VSX uses a combination of the old vector registers, the old FP
registers and new "second halves" of the FP registers.

Thus when we need to see the VSX state in the thread struct
(flush_vsx_to_thread()) or when we'll use the VSX in the kernel
(enable_kernel_vsx()) we need to ensure they are all flushed into
the thread struct if either of them is individually enabled.

Unfortunately we only tested if the whole VSX was enabled, not if they
were individually enabled.

Fixes: 72cd7b44bc99 ("powerpc: Uncomment and make enable_kernel_vsx() routine available")
Cc: stable@vger.kernel.org # v4.3+
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Michael Ellerman

powerpc/watchdog: add locking around init/exit functions

2017-08-09T13:45:33+00:00

When CPUs start and stop the watchdog, they manipulate shared data
that is normally protected by the lock. Other CPUs can be running
concurrently at this time, so it's a good idea to use locking here
to be on the safe side.

Remove the barrier which is undocumented and didn't do anything.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

powerpc/watchdog: Fix marking of stuck CPUs

2017-08-09T13:45:32+00:00

When the SMP detector finds other CPUs stuck, it iterates over
them and marks them as stuck. This pulls them out of the pending
mask and allows the detector to continue with remaining good
CPUs (if nmi_watchdog=panic is not enabled).

The code to dothat was buggy because when setting a CPU stuck,
if the pending mask became empty, it resets it to keep the
watchdog running. However the iterator will continue to run
over the new pending mask and mark remaining good CPUs sas stuck.

Fix this by doing it with cpumask bitwise operations.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

powerpc/watchdog: Fix final-check recovered case

2017-08-09T13:45:31+00:00

When the watchdog decides to panic, it takes the lock and double
checks everything (to avoid races with the CPU being unstuck or
panic()ed by something else).

The exit label was misplaced and would result in all-CPUs backtrace
and watchdog panic even in the case that the condition was found to be
resolved.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

powerpc/watchdog: Moderate touch_nmi_watchdog overhead

2017-08-09T13:45:29+00:00

Some code can go into a tight loop calling touch_nmi_watchdog (e.g.,
stop_machine CPU hotplug code). This can cause contention on watchdog
locks particularly if all CPUs with watchdog enabled are spinning in
the loops.

Avoid this storm of activity by running the watchdog timer callback
from this path if we have exceeded the timer period since it was last
run.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

powerpc/watchdog: Improve watchdog lock primitive

2017-08-09T13:45:28+00:00

- Hard-disable interrupts before taking the lock, which prevents
  soft-NMI re-entrancy and therefore can prevent deadlocks.
- Use raw_ variants of local_irq_disable to avoid irq debugging.
- When the lock is contended, spin at low SMT priority, using
  loads only, and with interrupts enabled (where possible).

Some stalls have been noticed at high loads that go away with improved
locking. There should not be so much locking contention in the first
place (which is addressed in a subsequent patch), but locking should
still be improved.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

powerpc: NMI IPI improve lock primitive

2017-08-09T13:45:26+00:00

When the NMI IPI lock is contended, spin at low SMT priority, using
loads only, and with interrupts enabled (where possible). This
improves behaviour under high contention (e.g., a system crash when
a number of CPUs are trying to enter the debugger).

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

Revert "powerpc/64: Avoid restore_math call if possible in syscall exit"

2017-08-07T11:36:56+00:00

This reverts commit bc4f65e4cf9d6cc43e0e9ba0b8648cf9201cd55f.

As reported by Andreas, this commit is causing unrecoverable SLB misses in the
system call exit path:

  Unrecoverable exception 4100 at c00000000000a1ec
  Oops: Unrecoverable exception, sig: 6 [#1]
  SMP NR_CPUS=2 PowerMac
  ...
  CPU: 0 PID: 18626 Comm: rm Not tainted 4.13.0-rc3 #1
  task: c00000018335e080 task.stack: c000000139e50000
  NIP: c00000000000a1ec LR: c00000000000a118 CTR: 0000000000000000
  REGS: c000000139e53bb0 TRAP: 4100   Not tainted  (4.13.0-rc3)
  MSR: 9000000000001030  CR: 24000044  XER: 20000000 SOFTE: 1
  GPR00: 0000000000000000 c000000139e53e30 c000000000abb500 fffffffffffffffe
  GPR04: c0000001eb866298 0000000000000000 0000000000000000 c00000018335e080
  GPR08: 900000000000d032 0000000000000000 0000000000000002 fffffffffffff001
  GPR12: c000000139e50000 c00000000ffff000 00003fffa8c0dca0 00003fffa8c0dc88
  GPR16: 0000000010000000 0000000000000001 00003fffa8c0eaa0 0000000000000000
  GPR20: 00003fffa8c27528 00003fffa8c27b00 0000000000000000 0000000000000000
  GPR24: 00003fffa8c0d918 00003ffff1b3efa0 00003fffa8c26d68 0000000000000000
  GPR28: 00003fffa8c249e8 00003fffa8c263d0 00003fffa8c27550 00003ffff1b3ef10
  NIP [c00000000000a1ec] system_call_exit+0xc0/0x21c
  LR [c00000000000a118] system_call+0x58/0x6c
  Call Trace:
  [c000000139e53e30] [c00000000000a118] system_call+0x58/0x6c (unreliable)
  Instruction dump:
  64a51000 7c6300d0 f8a101a0 4bffff9c 3c000000 60000006 780007c6 64000000
  60000000 7c004039 4082001c e8ed0170 <88070b78> 88c70b79 7c003214 2c200000

This is caused by us trying to load THREAD_LOAD_FP with MSR_RI=0, and taking an
SLB miss on the thread struct.

Reported-by: Andreas Schwab 
Diagnosed-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

powerpc/64: Fix __check_irq_replay missing decrementer interrupt

2017-08-04T02:55:49+00:00

If the decrementer wraps again and de-asserts the decrementer
exception while hard-disabled, __check_irq_replay() has a test to
notice the wrap when interrupts are re-enabled.

The decrementer check must be done when clearing the PACA_IRQ_HARD_DIS
flag, not when the PACA_IRQ_DEC flag is tested. Previously this worked
because the decrementer interrupt was always the first one checked
after clearing the hard disable flag, but HMI check was moved ahead of
that, which introduced this bug.

This can cause a missed decrementer interrupt if we soft-disable
interrupts then take an HMI which is recorded in irq_happened, then
hard-disable interrupts for > 4s to wrap the decrementer.

Fixes: e0e0d6b7390b ("powerpc/64: Replay hypervisor maintenance interrupt first")
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman

powerpc/perf: POWER9 PMU stops after idle workaround

2017-08-04T02:52:26+00:00

POWER9 DD2 PMU can stop after a state-loss idle in some conditions.

A solution is to set then clear MMCRA[60] after wake from state-loss
idle. MMCRA[60] is a non-architected bit, see the user manual for
details.

Signed-off-by: Nicholas Piggin 
Acked-by: Madhavan Srinivasan 
Reviewed-by: Vaidyanathan Srinivasan 
Acked-by: Anton Blanchard 
Signed-off-by: Michael Ellerman