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Subject[PATCH v4 1/2] irqchip/gic-v3-its: Track LPI distribution on a per CPU basis
Date
In order to improve the distribution of LPIs among CPUs, let start by
tracking the number of LPIs assigned to CPUs, both for managed and
non-managed interrupts (as separate counters).

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
drivers/irqchip/irq-gic-v3-its.c | 49 ++++++++++++++++++++++++++++++--
1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 124251b0ccba..4eb8441d0c2b 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -174,6 +174,13 @@ static struct {
int next_victim;
} vpe_proxy;

+struct cpu_lpi_count {
+ atomic_t managed;
+ atomic_t unmanaged;
+};
+
+static DEFINE_PER_CPU(struct cpu_lpi_count, cpu_lpi_count);
+
static LIST_HEAD(its_nodes);
static DEFINE_RAW_SPINLOCK(its_lock);
static struct rdists *gic_rdists;
@@ -1510,6 +1517,30 @@ static void its_unmask_irq(struct irq_data *d)
lpi_update_config(d, 0, LPI_PROP_ENABLED);
}

+static __maybe_unused u32 its_read_lpi_count(struct irq_data *d, int cpu)
+{
+ if (irqd_affinity_is_managed(d))
+ return atomic_read(&per_cpu_ptr(&cpu_lpi_count, cpu)->managed);
+
+ return atomic_read(&per_cpu_ptr(&cpu_lpi_count, cpu)->unmanaged);
+}
+
+static void its_inc_lpi_count(struct irq_data *d, int cpu)
+{
+ if (irqd_affinity_is_managed(d))
+ atomic_inc(&per_cpu_ptr(&cpu_lpi_count, cpu)->managed);
+ else
+ atomic_inc(&per_cpu_ptr(&cpu_lpi_count, cpu)->unmanaged);
+}
+
+static void its_dec_lpi_count(struct irq_data *d, int cpu)
+{
+ if (irqd_affinity_is_managed(d))
+ atomic_dec(&per_cpu_ptr(&cpu_lpi_count, cpu)->managed);
+ else
+ atomic_dec(&per_cpu_ptr(&cpu_lpi_count, cpu)->unmanaged);
+}
+
static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
bool force)
{
@@ -1518,34 +1549,44 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
struct its_device *its_dev = irq_data_get_irq_chip_data(d);
struct its_collection *target_col;
u32 id = its_get_event_id(d);
+ int prev_cpu;

/* A forwarded interrupt should use irq_set_vcpu_affinity */
if (irqd_is_forwarded_to_vcpu(d))
return -EINVAL;

+ prev_cpu = its_dev->event_map.col_map[id];
+ its_dec_lpi_count(d, prev_cpu);
+
/* lpi cannot be routed to a redistributor that is on a foreign node */
if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) {
if (its_dev->its->numa_node >= 0) {
cpu_mask = cpumask_of_node(its_dev->its->numa_node);
if (!cpumask_intersects(mask_val, cpu_mask))
- return -EINVAL;
+ goto err;
}
}

cpu = cpumask_any_and(mask_val, cpu_mask);

if (cpu >= nr_cpu_ids)
- return -EINVAL;
+ goto err;

/* don't set the affinity when the target cpu is same as current one */
- if (cpu != its_dev->event_map.col_map[id]) {
+ if (cpu != prev_cpu) {
target_col = &its_dev->its->collections[cpu];
its_send_movi(its_dev, target_col, id);
its_dev->event_map.col_map[id] = cpu;
irq_data_update_effective_affinity(d, cpumask_of(cpu));
}

+ its_inc_lpi_count(d, cpu);
+
return IRQ_SET_MASK_OK_DONE;
+
+err:
+ its_inc_lpi_count(d, prev_cpu);
+ return -EINVAL;
}

static u64 its_irq_get_msi_base(struct its_device *its_dev)
@@ -3448,6 +3489,7 @@ static int its_irq_domain_activate(struct irq_domain *domain,
cpu = cpumask_first(cpu_online_mask);
}

+ its_inc_lpi_count(d, cpu);
its_dev->event_map.col_map[event] = cpu;
irq_data_update_effective_affinity(d, cpumask_of(cpu));

@@ -3462,6 +3504,7 @@ static void its_irq_domain_deactivate(struct irq_domain *domain,
struct its_device *its_dev = irq_data_get_irq_chip_data(d);
u32 event = its_get_event_id(d);

+ its_dec_lpi_count(d, its_dev->event_map.col_map[event]);
/* Stop the delivery of interrupts */
its_send_discard(its_dev, event);
}
--
2.26.2
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