[PATCH 6.12.y] genirq/kexec: Do not take the bus lock of an interrupt chip on the crash path

[Thomas Gleixner <tglx@kernel.org>]

From: Igor Velkov <iav@iav.lv>

commit 717862eac6eff0eea8ac30a0c0de0bed84922aab upstream.

machine_kexec_mask_interrupts() calls irq_set_irqchip_state() for every
started interrupt. That function takes the bus lock of the chip and
desc->lock, and syncs the chip when it drops them. On the crash path
interrupts are off and the other CPUs are stopped, so a chip whose bus
transfer is completed by an interrupt never returns from the sync.

On RK3399 boards with an RK808 PMIC the RTC alarm interrupt belongs to
the regmap-irq chip of the RK808, which sits on I2C. rk808_irq_chip sets
init_ack_masked, so regmap_irq_sync_unlock() writes the ack register on
every unlock, and the I2C controller needs its own interrupt to finish
the transfer. A panic with a crash kernel loaded prints

  SMP: stopping secondary CPUs

and then nothing until the watchdog resets the board.

machine_kexec_mask_interrupts() takes neither lock for the other
operations on the descriptor. Move the search for the chip that
implements irq_set_irqchip_state() into __irq_set_irqchip_state(), which
takes no locks, and call it from machine_kexec_mask_interrupts().

Fixes: 78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()")
Suggested-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Igor Velkov <iav@iav.lv>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20261015-kexec-irq-bus-lock-v2-1-2af15f0757b6@iav.lv
---
 kernel/irq/internals.h |    1 +
 kernel/irq/kexec.c     |    2 +-
 kernel/irq/manage.c    |   49 +++++++++++++++++++++++++------------------------
 3 files changed, 27 insertions(+), 25 deletions(-)
---
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -75,6 +75,7 @@ enum {
 #include "settings.h"
 
 extern int __irq_set_trigger(struct irq_desc *desc, unsigned long flags);
+extern int __irq_set_irqchip_state(struct irq_desc *desc, enum irqchip_irq_state which, bool val);
 extern void __disable_irq(struct irq_desc *desc);
 extern void __enable_irq(struct irq_desc *desc);
 
--- a/kernel/irq/kexec.c
+++ b/kernel/irq/kexec.c
@@ -25,7 +25,7 @@ void machine_kexec_mask_interrupts(void)
 			 * First try to remove the active state from an interrupt which is forwarded
 			 * to a VM. If the interrupt is not forwarded, try to EOI the interrupt.
 			 */
-			check_eoi = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE, false);
+			check_eoi = __irq_set_irqchip_state(desc, IRQCHIP_STATE_ACTIVE, false);
 		}
 
 		if (check_eoi && chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -2854,6 +2854,28 @@ int irq_get_irqchip_state(unsigned int i
 }
 EXPORT_SYMBOL_GPL(irq_get_irqchip_state);
 
+int __irq_set_irqchip_state(struct irq_desc *desc, enum irqchip_irq_state which, bool val)
+{
+	struct irq_data *data = irq_desc_get_irq_data(desc);
+	struct irq_chip *chip;
+
+	do {
+		chip = irq_data_get_irq_chip(data);
+
+		if (WARN_ON_ONCE(!chip))
+			return -ENODEV;
+
+		if (chip->irq_set_irqchip_state)
+			break;
+
+		data = irqd_get_parent_data(data);
+	} while (data);
+
+	if (data)
+		return chip->irq_set_irqchip_state(data, which, val);
+	return -EINVAL;
+}
+
 /**
  *	irq_set_irqchip_state - set the state of a forwarded interrupt.
  *	@irq: Interrupt line that is forwarded to a VM
@@ -2870,36 +2892,15 @@ int irq_set_irqchip_state(unsigned int i
 			  bool val)
 {
 	struct irq_desc *desc;
-	struct irq_data *data;
-	struct irq_chip *chip;
 	unsigned long flags;
-	int err = -EINVAL;
+	int err;
 
 	desc = irq_get_desc_buslock(irq, &flags, 0);
 	if (!desc)
-		return err;
-
-	data = irq_desc_get_irq_data(desc);
-
-	do {
-		chip = irq_data_get_irq_chip(data);
-		if (WARN_ON_ONCE(!chip)) {
-			err = -ENODEV;
-			goto out_unlock;
-		}
-		if (chip->irq_set_irqchip_state)
-			break;
-#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
-		data = data->parent_data;
-#else
-		data = NULL;
-#endif
-	} while (data);
+		return -EINVAL;
 
-	if (data)
-		err = chip->irq_set_irqchip_state(data, which, val);
+	err = __irq_set_irqchip_state(desc, which, val);
 
-out_unlock:
 	irq_put_desc_busunlock(desc, flags);
 	return err;
 }