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Subject[PATCH v1 1/1] irqchip/gic-v3-its: fixup IRQ affinities to account for online CPUs
From
From: David Decotigny <ddecotig@google.com>

In some cases (eg. when booting with maxcpus=X), it is possible that
the preset IRQ affinity masks don't intersect with the set of online
CPUs. This patch extends the fallback strategy implemented when
IRQD_AFFINITY_MANAGED is not set to all cases. This is logged the
first time that happens.

Fixes: c5d6082d35e0 ("irqchip/gic-v3-its: Balance initial LPI affinity across CPUs")

---
drivers/irqchip/irq-gic-v3-its.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index cd772973114a..de862fd9ad73 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1618,11 +1618,6 @@ static int its_select_cpu(struct irq_data *d,
/* Try the intersection of the affinity and online masks */
cpumask_and(tmpmask, aff_mask, cpu_online_mask);

- /* If that doesn't fly, the online mask is the last resort */
- if (cpumask_empty(tmpmask))
- cpumask_copy(tmpmask, cpu_online_mask);
-
- cpu = cpumask_pick_least_loaded(d, tmpmask);
} else {
cpumask_and(tmpmask, irq_data_get_affinity_mask(d), cpu_online_mask);

@@ -1630,9 +1625,13 @@ static int its_select_cpu(struct irq_data *d,
if ((its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) &&
node != NUMA_NO_NODE)
cpumask_and(tmpmask, tmpmask, cpumask_of_node(node));
-
- cpu = cpumask_pick_least_loaded(d, tmpmask);
}
+
+ /* If that doesn't fly, the online mask is the last resort */
+ if (WARN_ON_ONCE(cpumask_empty(tmpmask)))
+ cpumask_copy(tmpmask, cpu_online_mask);
+
+ cpu = cpumask_pick_least_loaded(d, tmpmask);
out:
free_cpumask_var(tmpmask);

--
2.35.1.616.g0bdcbb4464-goog
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