[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-yui...@fujitsu.com>
---
 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