x86: Rework arch_disable_smp_support() for x86

Currently arch_disable_smp_support() on x86 disables only the
support for the IOAPIC and is also compiled in if SMP-support is
not.

Therefore this function is renamed to disable_ioapic_support(),
which meets its purpose and is only compiled in the kernel
when IOAPIC support is also.

A new arch_disable_smp_support() is created in smpboot.c,
which calls disable_ioapic_support() and gets only compiled
in the kernel when SMP support is also.

Signed-off-by: Henrik Kretzschmar <henne@nachtwindheim.de>
LKML-Reference: <1298385487-4708-3-git-send-email-henne@nachtwindheim.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/io_apic.h

@@ -175,6 +175,8 @@ extern void __init pre_init_apic_IRQ0(void);
 
 extern void mp_save_irq(struct mpc_intsrc *m);
 
+extern void disable_ioapic_support(void);
+
 #else  /* !CONFIG_X86_IO_APIC */
 
 #define io_apic_assign_pci_irqs 0
@@ -189,6 +191,7 @@ struct io_apic_irq_attr;
 static inline int io_apic_set_pci_routing(struct device *dev, int irq,
 		 struct io_apic_irq_attr *irq_attr) { return 0; }
 static inline void mp_save_irq(struct mpc_intsrc *m) { };
+static inline void disable_ioapic_support(void) { }
 #endif
 
 #endif /* _ASM_X86_IO_APIC_H */

arch/x86/kernel/apic/apic.c

@@ -43,6 +43,7 @@
 #include <asm/i8259.h>
 #include <asm/proto.h>
 #include <asm/apic.h>
+#include <asm/io_apic.h>
 #include <asm/desc.h>
 #include <asm/hpet.h>
 #include <asm/idle.h>
@@ -1209,7 +1210,7 @@ void __cpuinit setup_local_APIC(void)
 		rdtscll(tsc);
 
 	if (disable_apic) {
-		arch_disable_smp_support();
+		disable_ioapic_support();
 		return;
 	}
 

arch/x86/kernel/apic/io_apic.c

@@ -108,7 +108,10 @@ DECLARE_BITMAP(mp_bus_not_pci, MAX_MP_BUSSES);
 
 int skip_ioapic_setup;
 
-void arch_disable_smp_support(void)
+/**
+ * disable_ioapic_support() - disables ioapic support at runtime
+ */
+void disable_ioapic_support(void)
 {
 #ifdef CONFIG_PCI
 	noioapicquirk = 1;
@@ -120,7 +123,7 @@ void arch_disable_smp_support(void)
 static int __init parse_noapic(char *str)
 {
 	/* disable IO-APIC */
-	arch_disable_smp_support();
+	disable_ioapic_support();
 	return 0;
 }
 early_param("noapic", parse_noapic);

arch/x86/kernel/smpboot.c

@@ -64,6 +64,7 @@
 #include <asm/mtrr.h>
 #include <asm/mwait.h>
 #include <asm/apic.h>
+#include <asm/io_apic.h>
 #include <asm/setup.h>
 #include <asm/uv/uv.h>
 #include <linux/mc146818rtc.h>
@@ -945,6 +946,14 @@ int __cpuinit native_cpu_up(unsigned int cpu)
 	return 0;
 }
 
+/**
+ * arch_disable_smp_support() - disables SMP support for x86 at runtime
+ */
+void arch_disable_smp_support(void)
+{
+	disable_ioapic_support();
+}
+
 /*
  * Fall back to non SMP mode after errors.
  *
@@ -1045,7 +1054,7 @@ static int __init smp_sanity_check(unsigned max_cpus)
 				"(tell your hw vendor)\n");
 		}
 		smpboot_clear_io_apic();
-		arch_disable_smp_support();
+		disable_ioapic_support();
 		return -1;
 	}