linux-kernel - [tip: irq/core] genirq: Always limit the affinity to online CPUs

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Date:   Sun, 10 Apr 2022 19:12:59 -0000
From:   "tip-bot2 for Marc Zyngier" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: irq/core] genirq: Always limit the affinity to online CPUs

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     33de0aa4bae982ed6f7c777f86b5af3e627ac937
Gitweb:        https://git.kernel.org/tip/33de0aa4bae982ed6f7c777f86b5af3e627ac937
Author:        Marc Zyngier <maz@...nel.org>
AuthorDate:    Tue, 05 Apr 2022 19:50:39 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Sun, 10 Apr 2022 21:06:30 +02:00

genirq: Always limit the affinity to online CPUs

When booting with maxcpus=<small number> (or even loading a driver
while most CPUs are offline), it is pretty easy to observe managed
affinities containing a mix of online and offline CPUs being passed
to the irqchip driver.

This means that the irqchip cannot trust the affinity passed down
from the core code, which is a bit annoying and requires (at least
in theory) all drivers to implement some sort of affinity narrowing.

In order to address this, always limit the cpumask to the set of
online CPUs.

Signed-off-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/r/20220405185040.206297-3-maz@kernel.org

---
 kernel/irq/manage.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c03f71d..f71ecc1 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -222,11 +222,16 @@ int irq_do_set_affinity(struct irq_data *data, const struct cpumask *mask,
 {
 	struct irq_desc *desc = irq_data_to_desc(data);
 	struct irq_chip *chip = irq_data_get_irq_chip(data);
+	const struct cpumask  *prog_mask;
 	int ret;
 
+	static DEFINE_RAW_SPINLOCK(tmp_mask_lock);
+	static struct cpumask tmp_mask;
+
 	if (!chip || !chip->irq_set_affinity)
 		return -EINVAL;
 
+	raw_spin_lock(&tmp_mask_lock);
 	/*
 	 * If this is a managed interrupt and housekeeping is enabled on
 	 * it check whether the requested affinity mask intersects with
@@ -248,24 +253,28 @@ int irq_do_set_affinity(struct irq_data *data, const struct cpumask *mask,
 	 */
 	if (irqd_affinity_is_managed(data) &&
 	    housekeeping_enabled(HK_TYPE_MANAGED_IRQ)) {
-		const struct cpumask *hk_mask, *prog_mask;
-
-		static DEFINE_RAW_SPINLOCK(tmp_mask_lock);
-		static struct cpumask tmp_mask;
+		const struct cpumask *hk_mask;
 
 		hk_mask = housekeeping_cpumask(HK_TYPE_MANAGED_IRQ);
 
-		raw_spin_lock(&tmp_mask_lock);
 		cpumask_and(&tmp_mask, mask, hk_mask);
 		if (!cpumask_intersects(&tmp_mask, cpu_online_mask))
 			prog_mask = mask;
 		else
 			prog_mask = &tmp_mask;
-		ret = chip->irq_set_affinity(data, prog_mask, force);
-		raw_spin_unlock(&tmp_mask_lock);
 	} else {
-		ret = chip->irq_set_affinity(data, mask, force);
+		prog_mask = mask;
 	}
+
+	/* Make sure we only provide online CPUs to the irqchip */
+	cpumask_and(&tmp_mask, prog_mask, cpu_online_mask);
+	if (!cpumask_empty(&tmp_mask))
+		ret = chip->irq_set_affinity(data, &tmp_mask, force);
+	else
+		ret = -EINVAL;
+
+	raw_spin_unlock(&tmp_mask_lock);
+
 	switch (ret) {
 	case IRQ_SET_MASK_OK:
 	case IRQ_SET_MASK_OK_DONE: