[tip: irq/drivers] irqchip/jcore-aic: Fix lost IPIs on SMP

[tip-bot2 for Karl Mehltretter]

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

Commit-ID:     f556f008f704a8777c73fb3a4177dc57c0dbe769
Gitweb:        https://git.kernel.org/tip/f556f008f704a8777c73fb3a4177dc57c0dbe769
Author:        Karl Mehltretter <kmehltretter@xxxxxxxxx>
AuthorDate:    Mon, 28 Sep 2026 05:54:08 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxx>
CommitterDate: Thu, 15 Oct 2026 11:59:22 +02:00

irqchip/jcore-aic: Fix lost IPIs on SMP

Since commit bdf4e2ac295fe ("genirq: Allow per-cpu interrupt sharing for
non-overlapping affinities"), handle_percpu_devid_irq() only runs an
action whose affinity mask contains the current CPU. Only actions set up
through the percpu_devid request functions have such a mask.

handle_jcore_irq() passes every per-CPU interrupt to
handle_percpu_devid_irq(). The J2 IPI is not a percpu_devid interrupt.
j2_prepare_cpus() requests it with request_irq() and IRQF_PERCPU, so its
action has no affinity mask and cpumask_test_cpu() reads through a NULL
pointer. J2 has no MMU to catch this. The read returns whatever is at
address 0, the action is not found, and IPIs are dropped as spurious
("Spurious percpu IRQ20 on CPU1", printed once).

Pass only percpu_devid interrupts (the PIT) to handle_percpu_devid_irq()
and the other per-CPU interrupts to handle_percpu_irq() again, as before
commit d7e3fd658248f ("irqchip/jcore-aic, clocksource/drivers/jcore: Fix
jcore-pit interrupt request").

Found with a two-CPU J2 model simulated from the J-Core RTL. Without
this change the boot stalls with both CPUs idle shortly after
"smp: Brought up 1 node, 2 CPUs". With it, the boot reaches userspace.

Fixes: bdf4e2ac295fe ("genirq: Allow per-cpu interrupt sharing for non-overlapping affinities")
Signed-off-by: Karl Mehltretter <kmehltretter@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Assisted-by: LLM
Tested-by: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://patch.msgid.link/20260928035408.25871-1-kmehltretter@xxxxxxxxx
---
 drivers/irqchip/irq-jcore-aic.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-jcore-aic.c b/drivers/irqchip/irq-jcore-aic.c
index 94c05cf..b4fee02 100644
--- a/drivers/irqchip/irq-jcore-aic.c
+++ b/drivers/irqchip/irq-jcore-aic.c
@@ -37,8 +37,10 @@ static struct irq_chip jcore_aic;
 
 static void handle_jcore_irq(struct irq_desc *desc)
 {
-	if (irqd_is_per_cpu(irq_desc_get_irq_data(desc)))
+	if (irq_is_percpu_devid(irq_desc_get_irq(desc)))
 		handle_percpu_devid_irq(desc);
+	else if (irqd_is_per_cpu(irq_desc_get_irq_data(desc)))
+		handle_percpu_irq(desc);
 	else
 		handle_simple_irq(desc);
 }