[PATCH 2/2] Register IPI_CPU_CRASH_STOP IPI as pseudo-NMI

[Yuichi Ito]

Register IPI_CPU_CRASH_STOP IPI as pseudo-NMI.
For systems that do not support pseudo-NMI, register as a normal IRQ.

Signed-off-by: Yuichi Ito <ito-yuichi@xxxxxxxxxxx>
---
 arch/arm64/kernel/smp.c | 39 +++++++++++++++++++++++++++++++--------
 1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index b6bde2675ccc..d929dd7221ff 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -79,6 +79,8 @@ enum ipi_msg_type {
 static int ipi_irq_base __read_mostly;
 static int nr_ipi __read_mostly = NR_IPI;
 static struct irq_desc *ipi_desc[NR_IPI] __read_mostly;
+static int ipi_crash_stop = -1;
+static int ipi_crash_stop_enable_nmi;
 
 static void ipi_setup(int cpu);
 static void ipi_teardown(int cpu);
@@ -954,8 +956,16 @@ static void ipi_setup(int cpu)
 	if (WARN_ON_ONCE(!ipi_irq_base))
 		return;
 
-	for (i = 0; i < nr_ipi; i++)
-		enable_percpu_irq(ipi_irq_base + i, 0);
+	for (i = 0; i < nr_ipi; i++) {
+		if (ipi_irq_base + i == ipi_crash_stop) {
+			if (!prepare_percpu_nmi(ipi_irq_base + i)) {
+				enable_percpu_nmi(ipi_irq_base + i, 0);
+				ipi_crash_stop_enable_nmi = 1;
+			} else
+				pr_crit("CPU%u: IPI_CPU_CRASH_STOP cannot be enabled NMI.\n", cpu);
+		} else
+			enable_percpu_irq(ipi_irq_base + i, 0);
+	}
 }
 
 static void ipi_teardown(int cpu)
@@ -965,23 +975,37 @@ static void ipi_teardown(int cpu)
 	if (WARN_ON_ONCE(!ipi_irq_base))
 		return;
 
-	for (i = 0; i < nr_ipi; i++)
-		disable_percpu_irq(ipi_irq_base + i);
+	for (i = 0; i < nr_ipi; i++) {
+		if (ipi_irq_base + i == ipi_crash_stop) {
+			if (ipi_crash_stop_enable_nmi) {
+				disable_percpu_nmi(ipi_irq_base + i);
+				teardown_percpu_nmi(ipi_irq_base + i);
+			}
+		} else
+			disable_percpu_irq(ipi_irq_base + i);
+	}
 }
 
 void __init set_smp_ipi_range(int ipi_base, int n)
 {
-	int i;
+	int i, ret;
 
 	WARN_ON(n < NR_IPI);
 	nr_ipi = min(n, NR_IPI);
 
+	ret = request_percpu_nmi(ipi_base + IPI_CPU_CRASH_STOP,
+				 ipi_handler, "IPI", &cpu_number);
+	if (!ret)
+		ipi_crash_stop = ipi_base + IPI_CPU_CRASH_STOP;
+
 	for (i = 0; i < nr_ipi; i++) {
 		int err;
 
-		err = request_percpu_irq(ipi_base + i, ipi_handler,
-					 "IPI", &cpu_number);
-		WARN_ON(err);
+		if (ipi_base + i != ipi_crash_stop) {
+			err = request_percpu_irq(ipi_base + i, ipi_handler,
+						 "IPI", &cpu_number);
+			WARN_ON(err);
+		}
 
 		ipi_desc[i] = irq_to_desc(ipi_base + i);
 		irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);
-- 
2.25.1