linux-kernel - [PATCH v2 3/7] irqchip/gic-v3-its: Avoid explicit cpumask allocation on stack

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Message-Id: <20240416085454.3547175-4-dawei.li@shingroup.cn>
Date: Tue, 16 Apr 2024 16:54:50 +0800
From: Dawei Li <dawei.li@...ngroup.cn>
To: tglx@...utronix.de,
	yury.norov@...il.com,
	rafael@...nel.org
Cc: akpm@...ux-foundation.org,
	maz@...nel.org,
	florian.fainelli@...adcom.com,
	chenhuacai@...nel.org,
	jiaxun.yang@...goat.com,
	anup@...infault.org,
	palmer@...belt.com,
	samuel.holland@...ive.com,
	linux@...musvillemoes.dk,
	daniel.lezcano@...aro.org,
	linux-kernel@...r.kernel.org,
	Dawei Li <dawei.li@...ngroup.cn>
Subject: [PATCH v2 3/7] irqchip/gic-v3-its: Avoid explicit cpumask allocation on stack

In general it's preferable to avoid placing cpumasks on the stack, as
for large values of NR_CPUS these can consume significant amounts of
stack space and make stack overflows more likely.

Remove cpumask var on stack and use cpumask_any_and() to address it.

Signed-off-by: Dawei Li <dawei.li@...ngroup.cn>
---
 drivers/irqchip/irq-gic-v3-its.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index fca888b36680..20f954211c61 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3826,9 +3826,9 @@ static int its_vpe_set_affinity(struct irq_data *d,
 				bool force)
 {
 	struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
-	struct cpumask common, *table_mask;
+	unsigned int from, cpu = nr_cpu_ids;
+	struct cpumask *table_mask;
 	unsigned long flags;
-	int from, cpu;
 
 	/*
 	 * Changing affinity is mega expensive, so let's be as lazy as
@@ -3850,10 +3850,15 @@ static int its_vpe_set_affinity(struct irq_data *d,
 	 * If we are offered another CPU in the same GICv4.1 ITS
 	 * affinity, pick this one. Otherwise, any CPU will do.
 	 */
-	if (table_mask && cpumask_and(&common, mask_val, table_mask))
-		cpu = cpumask_test_cpu(from, &common) ? from : cpumask_first(&common);
-	else
+	if (table_mask)
+		cpu = cpumask_any_and(mask_val, table_mask);
+	if (cpu < nr_cpu_ids) {
+		if (cpumask_test_cpu(from, mask_val) &&
+		    cpumask_test_cpu(from, table_mask))
+			cpu = from;
+	} else {
 		cpu = cpumask_first(mask_val);
+	}
 
 	if (from == cpu)
 		goto out;
-- 
2.27.0