[tip: irq/core] genirq/kexec: Prevent redundant IRQ masking by checking state before shutdown

[tip-bot2 for Eliav Farber]

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

Commit-ID:     b4706d814921cc2df7bb59ad8f9ee84855a4f0c4
Gitweb:        https://git.kernel.org/tip/b4706d814921cc2df7bb59ad8f9ee84855a4f0c4
Author:        Eliav Farber <farbere@xxxxxxxxxx>
AuthorDate:    Wed, 04 Dec 2024 14:20:03 
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Wed, 11 Dec 2024 20:32:34 +01:00

genirq/kexec: Prevent redundant IRQ masking by checking state before shutdown

During machine kexec, machine_kexec_mask_interrupts() is responsible for
disabling or masking all interrupts. While the irq_disable() is only
invoked when the interrupt is not yet disabled, it unconditionally invokes
the irq_mask() callback for every interrupt descriptor, even when the
interrupt is already masked or not even started up yet.

A specific issue was observed in the crash kernel flow after unbinding a
device (prior to kexec) that used a GPIO as an IRQ source. The warning was
triggered by the gpiochip_disable_irq() function, which attempts to clear
the FLAG_IRQ_IS_ENABLED flag when FLAG_USED_AS_IRQ was not set.

This issue surfaced after commit a8173820f441 ("gpio: gpiolib: Allow GPIO
IRQs to lazy disable") introduced lazy disablement for GPIO IRQs. It
replaced disable/enable hooks with mask/unmask hooks. Unlike the disable
hook, the mask hook doesn't handle already-masked IRQs.

When a GPIO-IRQ driver is unbound, the IRQ is released, triggering
__irq_disable() and irq_state_set_masked(). A subsequent call to
machine_kexec_mask_interrupts() re-invokes chip->irq_mask(). This results
in a call chain, including gpiochip_irq_mask() and gpiochip_disable_irq().
Since FLAG_USED_AS_IRQ was cleared earlier, the warning is triggered.

Replace the direct invocation of the irq_mask() and irq_disable() callbacks
invoking to irq_shutdown(), which handles the cases correct and avoid it
all together when the interrupt has never been started up.

Signed-off-by: Eliav Farber <farbere@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20241204142003.32859-3-farbere@xxxxxxxxxx

---
 kernel/irq/kexec.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/irq/kexec.c b/kernel/irq/kexec.c
index 0f9548c..1a3deff 100644
--- a/kernel/irq/kexec.c
+++ b/kernel/irq/kexec.c
@@ -17,7 +17,7 @@ void machine_kexec_mask_interrupts(void)
 		int check_eoi = 1;
 
 		chip = irq_desc_get_chip(desc);
-		if (!chip)
+		if (!chip || !irqd_is_started(&desc->irq_data))
 			continue;
 
 		if (IS_ENABLED(CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD)) {
@@ -31,10 +31,6 @@ void machine_kexec_mask_interrupts(void)
 		if (check_eoi && chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
 			chip->irq_eoi(&desc->irq_data);
 
-		if (chip->irq_mask)
-			chip->irq_mask(&desc->irq_data);
-
-		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
-			chip->irq_disable(&desc->irq_data);
+		irq_shutdown(desc);
 	}
 }