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powerpc/xive: Fix the size of the cpumask used in xive_find_target_in_mask()

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When called from xive_irq_startup(), the size of the cpumask can be
larger than nr_cpu_ids. This can result in a WARN_ON such as:

  WARNING: CPU: 10 PID: 1 at ../arch/powerpc/sysdev/xive/common.c:476 xive_find_target_in_mask+0x110/0x2f0
  ...
  NIP [c00000000008a310] xive_find_target_in_mask+0x110/0x2f0
  LR [c00000000008a2e4] xive_find_target_in_mask+0xe4/0x2f0
  Call Trace:
    xive_find_target_in_mask+0x74/0x2f0 (unreliable)
    xive_pick_irq_target.isra.1+0x200/0x230
    xive_irq_startup+0x60/0x180
    irq_startup+0x70/0xd0
    __setup_irq+0x7bc/0x880
    request_threaded_irq+0x14c/0x2c0
    request_event_sources_irqs+0x100/0x180
    __machine_initcall_pseries_init_ras_IRQ+0x104/0x134
    do_one_initcall+0x68/0x1d0
    kernel_init_freeable+0x290/0x374
    kernel_init+0x24/0x170
    ret_from_kernel_thread+0x5c/0x74

This happens because we're being called with our affinity mask set to
irq_default_affinity. That in turn was populated using
cpumask_setall(), which sets NR_CPUs worth of bits, not nr_cpu_ids
worth. Finally cpumask_weight() will return > nr_cpu_ids when passed a
mask which has > nr_cpu_ids bits set.

Fix it by limiting the value returned by cpumask_weight().

Signed-off-by: Cédric Le Goater <clg@kaod.org>
[mpe: Add change log details on actual cause]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Cédric Le Goater 2017-08-08 11:02:49 +02:00 committed by Michael Ellerman
parent d1d0d5ffb3
commit a9dadc1c51
1 changed files with 1 additions and 1 deletions
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2
arch/powerpc/sysdev/xive/common.c
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@ -447,7 +447,7 @@ static int xive_find_target_in_mask(const struct cpumask *mask,
int cpu, first, num, i;
/* Pick up a starting point CPU in the mask based on fuzz */
num = cpumask_weight(mask);
num = min_t(int, cpumask_weight(mask), nr_cpu_ids);
first = fuzz % num;
/* Locate it */