x86/apic: Provide and use helper for send_IPI_allbutself()

To support IPI shorthands wrap invocations of apic->send_IPI_allbutself()
in a helper function, so the static key controlling the shorthand mode is
only in one place.

Fixup all callers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105220.492691679@linutronix.de

arch/x86/include/asm/apic.h

@@ -177,6 +177,8 @@ extern void lapic_online(void);
 extern void lapic_offline(void);
 extern bool apic_needs_pit(void);
 
+extern void apic_send_IPI_allbutself(unsigned int vector);
+
 #else /* !CONFIG_X86_LOCAL_APIC */
 static inline void lapic_shutdown(void) { }
 #define local_apic_timer_c2_ok		1

arch/x86/kernel/apic/ipi.c

@@ -50,6 +50,18 @@ void apic_smt_update(void)
 		static_branch_enable(&apic_use_ipi_shorthand);
 	}
 }
+
+void apic_send_IPI_allbutself(unsigned int vector)
+{
+	if (num_online_cpus() < 2)
+		return;
+
+	if (static_branch_likely(&apic_use_ipi_shorthand))
+		apic->send_IPI_allbutself(vector);
+	else
+		apic->send_IPI_mask_allbutself(cpu_online_mask, vector);
+}
+
 #endif /* CONFIG_SMP */
 
 static inline int __prepare_ICR2(unsigned int mask)

arch/x86/kernel/kgdb.c

@@ -416,7 +416,7 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs)
  */
 void kgdb_roundup_cpus(void)
 {
-	apic->send_IPI_allbutself(NMI_VECTOR);
+	apic_send_IPI_allbutself(NMI_VECTOR);
 }
 #endif
 

arch/x86/kernel/reboot.c

@@ -828,11 +828,6 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
 	return NMI_HANDLED;
 }
 
-static void smp_send_nmi_allbutself(void)
-{
-	apic->send_IPI_allbutself(NMI_VECTOR);
-}
-
 /*
  * Halt all other CPUs, calling the specified function on each of them
  *
@@ -861,7 +856,7 @@ void nmi_shootdown_cpus(nmi_shootdown_cb callback)
 	 */
 	wmb();
 
-	smp_send_nmi_allbutself();
+	apic_send_IPI_allbutself(NMI_VECTOR);
 
 	/* Kick CPUs looping in NMI context. */
 	WRITE_ONCE(crash_ipi_issued, 1);

arch/x86/kernel/smp.c

@@ -215,7 +215,7 @@ static void native_stop_other_cpus(int wait)
 		/* sync above data before sending IRQ */
 		wmb();
 
-		apic->send_IPI_allbutself(REBOOT_VECTOR);
+		apic_send_IPI_allbutself(REBOOT_VECTOR);
 
 		/*
 		 * Don't wait longer than a second for IPI completion. The
@@ -241,7 +241,7 @@ static void native_stop_other_cpus(int wait)
 
 			pr_emerg("Shutting down cpus with NMI\n");
 
-			apic->send_IPI_allbutself(NMI_VECTOR);
+			apic_send_IPI_allbutself(NMI_VECTOR);
 		}
 		/*
 		 * Don't wait longer than 10 ms if the caller didn't