[patch 18/18] x86/apic/x2apic: Add conditional IPI shorthands support

[Thomas Gleixner <tglx@linutronix.de>]

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@linutronix.de>
---
 arch/x86/kernel/apic/local.h          |    1 +
 arch/x86/kernel/apic/x2apic_cluster.c |   10 ++++++++--
 arch/x86/kernel/apic/x2apic_phys.c    |   18 ++++++++++++++++--
 3 files changed, 25 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/apic/local.h
+++ b/arch/x86/kernel/apic/local.h
@@ -23,6 +23,7 @@ unsigned int x2apic_get_apic_id(unsigned
 u32 x2apic_set_apic_id(unsigned int id);
 int x2apic_phys_pkg_id(int initial_apicid, int index_msb);
 void x2apic_send_IPI_self(int vector);
+void __x2apic_send_IPI_shorthand(int vector, u32 which);
 
 /* IPI */
 
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -82,12 +82,18 @@ x2apic_send_IPI_mask_allbutself(const st
 
 static void x2apic_send_IPI_allbutself(int vector)
 {
-	__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLBUT);
+	if (static_branch_likely(&apic_use_ipi_shorthand))
+		__x2apic_send_IPI_shorthand(vector, APIC_DEST_ALLBUT);
+	else
+		__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLBUT);
 }
 
 static void x2apic_send_IPI_all(int vector)
 {
-	__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLINC);
+	if (static_branch_likely(&apic_use_ipi_shorthand))
+		__x2apic_send_IPI_shorthand(vector, APIC_DEST_ALLINC);
+	else
+		__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLINC);
 }
 
 static u32 x2apic_calc_apicid(unsigned int cpu)
--- a/arch/x86/kernel/apic/x2apic_phys.c
+++ b/arch/x86/kernel/apic/x2apic_phys.c
@@ -75,12 +75,18 @@ static void
 
 static void x2apic_send_IPI_allbutself(int vector)
 {
-	__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLBUT);
+	if (static_branch_likely(&apic_use_ipi_shorthand))
+		__x2apic_send_IPI_shorthand(vector, APIC_DEST_ALLBUT);
+	else
+		__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLBUT);
 }
 
 static void x2apic_send_IPI_all(int vector)
 {
-	__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLINC);
+	if (static_branch_likely(&apic_use_ipi_shorthand))
+		__x2apic_send_IPI_shorthand(vector, APIC_DEST_ALLINC);
+	else
+		__x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLINC);
 }
 
 static void init_x2apic_ldr(void)
@@ -112,6 +118,14 @@ void __x2apic_send_IPI_dest(unsigned int
 	native_x2apic_icr_write(cfg, apicid);
 }
 
+void __x2apic_send_IPI_shorthand(int vector, u32 which)
+{
+	unsigned long cfg = __prepare_ICR(which, vector, 0);
+
+	x2apic_wrmsr_fence();
+	native_x2apic_icr_write(cfg, 0);
+}
+
 unsigned int x2apic_get_apic_id(unsigned long id)
 {
 	return id;