[patch 16/18] x86/apic: Convert 32bit to IPI shorthand static key

[Thomas Gleixner]

Broadcast now depends on the fact that all present CPUs have been booted
once so handling broadcast IPIs is not doing any harm. In case that a CPU
is offline, it does not react to regular IPIs and the NMI handler returns
early.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/ipi.c |   12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

--- a/arch/x86/kernel/apic/ipi.c
+++ b/arch/x86/kernel/apic/ipi.c
@@ -8,13 +8,7 @@
 DEFINE_STATIC_KEY_FALSE(apic_use_ipi_shorthand);
 
 #ifdef CONFIG_SMP
-#ifdef CONFIG_HOTPLUG_CPU
-#define DEFAULT_SEND_IPI	(1)
-#else
-#define DEFAULT_SEND_IPI	(0)
-#endif
-
-static int apic_ipi_shorthand_off __ro_after_init = DEFAULT_SEND_IPI;
+static int apic_ipi_shorthand_off __ro_after_init;
 
 static __init int apic_ipi_shorthand(char *str)
 {
@@ -250,7 +244,7 @@ void default_send_IPI_allbutself(int vec
 	if (num_online_cpus() < 2)
 		return;
 
-	if (apic_ipi_shorthand_off || vector == NMI_VECTOR) {
+	if (static_branch_likely(&apic_use_ipi_shorthand)) {
 		apic->send_IPI_mask_allbutself(cpu_online_mask, vector);
 	} else {
 		__default_send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
@@ -259,7 +253,7 @@ void default_send_IPI_allbutself(int vec
 
 void default_send_IPI_all(int vector)
 {
-	if (apic_ipi_shorthand_off || vector == NMI_VECTOR) {
+	if (static_branch_likely(&apic_use_ipi_shorthand)) {
 		apic->send_IPI_mask(cpu_online_mask, vector);
 	} else {
 		__default_send_IPI_shortcut(APIC_DEST_ALLINC, vector);