linux-kernel - [patch 17/18] x86/apic/flat64: Add conditional IPI shorthands support

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Date:   Wed, 03 Jul 2019 12:54:48 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Nadav Amit <namit@...are.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Feng Tang <feng.tang@...el.com>
Subject: [patch 17/18] x86/apic/flat64: Add conditional IPI shorthands support

Use the shorthand broadcast delivery if the static key controlling it is
enabled. If not use the regular one by one IPI mechanism.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/apic/apic_flat_64.c |   24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

--- a/arch/x86/kernel/apic/apic_flat_64.c
+++ b/arch/x86/kernel/apic/apic_flat_64.c
@@ -80,7 +80,9 @@ static void flat_send_IPI_allbutself(int
 {
 	int cpu = smp_processor_id();
 
-	if (IS_ENABLED(CONFIG_HOTPLUG_CPU) || vector == NMI_VECTOR) {
+	if (static_branch_likely(&apic_use_ipi_shorthand)) {
+		__default_send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
+	} else {
 		if (!cpumask_equal(cpu_online_mask, cpumask_of(cpu))) {
 			unsigned long mask = cpumask_bits(cpu_online_mask)[0];
 
@@ -89,18 +91,15 @@ static void flat_send_IPI_allbutself(int
 
 			_flat_send_IPI_mask(mask, vector);
 		}
-	} else if (num_online_cpus() > 1) {
-		__default_send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
 	}
 }
 
 static void flat_send_IPI_all(int vector)
 {
-	if (vector == NMI_VECTOR) {
-		flat_send_IPI_mask(cpu_online_mask, vector);
-	} else {
+	if (static_branch_likely(&apic_use_ipi_shorthand))
 		__default_send_IPI_shortcut(APIC_DEST_ALLINC, vector);
-	}
+	else
+		flat_send_IPI_mask(cpu_online_mask, vector);
 }
 
 static unsigned int flat_get_apic_id(unsigned long x)
@@ -218,12 +217,19 @@ static void physflat_init_apic_ldr(void)
 
 static void physflat_send_IPI_allbutself(int vector)
 {
-	default_send_IPI_mask_allbutself_phys(cpu_online_mask, vector);
+	if (static_branch_likely(&apic_use_ipi_shorthand)) {
+		__default_send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
+	} else {
+		default_send_IPI_mask_allbutself_phys(cpu_online_mask, vector);
+	}
 }
 
 static void physflat_send_IPI_all(int vector)
 {
-	default_send_IPI_mask_sequence_phys(cpu_online_mask, vector);
+	if (static_branch_likely(&apic_use_ipi_shorthand))
+		__default_send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
+	else
+		default_send_IPI_mask_sequence_phys(cpu_online_mask, vector);
 }
 
 static int physflat_probe(void)