8 files changed, 51 insertions, 21 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1042d69b267..bce241fe1d2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -235,6 +235,20 @@ config SMP
 
           If you don't know what to do here, say N.
 
+config X86_X2APIC
+        bool "Support x2apic"
+        depends on X86_LOCAL_APIC && X86_64
+        ---help---
+          This enables x2apic support on CPUs that have this feature.
+
+          This allows 32-bit apic IDs (so it can support very large systems),
+          and accesses the local apic via MSRs not via mmio.
+
+          ( On certain CPU models you may need to enable INTR_REMAP too,
+            to get functional x2apic mode. )
+
+          If you don't know what to do here, say N.
+
 config SPARSE_IRQ
         bool "Support sparse irq numbering"
         depends on PCI_MSI || HT_IRQ
@@ -1828,6 +1842,7 @@ config DMAR_FLOPPY_WA
 config INTR_REMAP
         bool "Support for Interrupt Remapping (EXPERIMENTAL)"
         depends on X86_64 && X86_IO_APIC && PCI_MSI && ACPI && EXPERIMENTAL
+        select X86_X2APIC
         ---help---
           Supports Interrupt remapping for IO-APIC and MSI devices.
           To use x2apic mode in the CPU's which support x2APIC enhancements or
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index fba49f66228..dc1db99cd40 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -112,7 +112,7 @@ static inline u32 native_apic_msr_read(u32 reg)
         return low;
 }
 
-#ifndef CONFIG_X86_32
+#ifdef CONFIG_X86_X2APIC
 extern int x2apic;
 extern void check_x2apic(void);
 extern void enable_x2apic(void);
@@ -131,7 +131,19 @@ static inline int x2apic_enabled(void)
         return 0;
 }
 #else
-#define x2apic_enabled()        0
+static inline void check_x2apic(void)
+{
+}
+static inline void enable_x2apic(void)
+{
+}
+static inline void enable_IR_x2apic(void)
+{
+}
+static inline int x2apic_enabled(void)
+{
+        return 0;
+}
 #endif
 
 struct apic_ops {
@@ -177,7 +189,7 @@ static inline u32 safe_apic_wait_icr_idle(void)
 
 extern int get_physical_broadcast(void);
 
-#ifdef CONFIG_X86_64
+#ifdef CONFIG_X86_X2APIC
 static inline void ack_x2APIC_irq(void)
 {
         /* Docs say use 0 for future compatibility */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 24f357e7557..1cefd218f76 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -117,8 +117,8 @@ obj-$(CONFIG_SWIOTLB)			+= pci-swiotlb_64.o # NB rename without _64
 # 64 bit specific files
 ifeq ($(CONFIG_X86_64),y)
         obj-y                           += genapic_64.o genapic_flat_64.o
-        obj-y                           += genx2apic_cluster.o
-        obj-y                           += genx2apic_phys.o
+        obj-$(CONFIG_X86_X2APIC)        += genx2apic_cluster.o
+        obj-$(CONFIG_X86_X2APIC)        += genx2apic_phys.o
         obj-$(CONFIG_X86_UV)            += genx2apic_uv_x.o tlb_uv.o
         obj-$(CONFIG_X86_UV)            += bios_uv.o uv_irq.o uv_sysfs.o
         obj-$(CONFIG_X86_PM_TIMER)      += pmtimer_64.o
diff --git a/arch/x86/kernel/apic.c b/arch/x86/kernel/apic.c
index a894eea9d51..004aa1c31e4 100644
--- a/arch/x86/kernel/apic.c
+++ b/arch/x86/kernel/apic.c
@@ -112,11 +112,7 @@ static __init int setup_apicpmtimer(char *s)
 __setup("apicpmtimer", setup_apicpmtimer);
 #endif
 
-#ifdef CONFIG_X86_64
-#define HAVE_X2APIC
-#endif
-
-#ifdef HAVE_X2APIC
+#ifdef CONFIG_X86_X2APIC
 int x2apic;
 /* x2apic enabled before OS handover */
 static int x2apic_preenabled;
@@ -269,7 +265,7 @@ static struct apic_ops xapic_ops = {
 struct apic_ops __read_mostly *apic_ops = &xapic_ops;
 EXPORT_SYMBOL_GPL(apic_ops);
 
-#ifdef HAVE_X2APIC
+#ifdef CONFIG_X86_X2APIC
 static void x2apic_wait_icr_idle(void)
 {
         /* no need to wait for icr idle in x2apic */
@@ -1320,11 +1316,14 @@ void __cpuinit end_local_APIC_setup(void)
         apic_pm_activate();
 }
 
-#ifdef HAVE_X2APIC
+#ifdef CONFIG_X86_X2APIC
 void check_x2apic(void)
 {
         int msr, msr2;
 
+        if (!cpu_has_x2apic)
+                return;
+
         rdmsr(MSR_IA32_APICBASE, msr, msr2);
 
         if (msr & X2APIC_ENABLE) {
@@ -1338,6 +1337,9 @@ void enable_x2apic(void)
 {
         int msr, msr2;
 
+        if (!x2apic)
+                return;
+
         rdmsr(MSR_IA32_APICBASE, msr, msr2);
         if (!(msr & X2APIC_ENABLE)) {
                 pr_info("Enabling x2apic\n");
@@ -1439,7 +1441,7 @@ end:
 
         return;
 }
-#endif /* HAVE_X2APIC */
+#endif /* CONFIG_X86_X2APIC */
 
 #ifdef CONFIG_X86_64
 /*
@@ -1570,7 +1572,7 @@ void __init early_init_lapic_mapping(void)
  */
 void __init init_apic_mappings(void)
 {
-#ifdef HAVE_X2APIC
+#ifdef CONFIG_X86_X2APIC
         if (x2apic) {
                 boot_cpu_physical_apicid = read_apic_id();
                 return;
@@ -1634,9 +1636,7 @@ int __init APIC_init_uniprocessor(void)
         }
 #endif
 
-#ifdef HAVE_X2APIC
         enable_IR_x2apic();
-#endif
 #ifdef CONFIG_X86_64
         default_setup_apic_routing();
 #endif
@@ -2021,7 +2021,7 @@ static int lapic_resume(struct sys_device *dev)
 
         local_irq_save(flags);
 
-#ifdef HAVE_X2APIC
+#ifdef CONFIG_X86_X2APIC
         if (x2apic)
                 enable_x2apic();
         else
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4db150ed446..4b5d13e472d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1051,7 +1051,7 @@ void __cpuinit cpu_init(void)
         barrier();
 
         check_efer();
-        if (cpu != 0 && x2apic)
+        if (cpu != 0)
                 enable_x2apic();
 
         /*
diff --git a/arch/x86/kernel/genapic_64.c b/arch/x86/kernel/genapic_64.c
index 820dea5d0eb..cdc4772d9c8 100644
--- a/arch/x86/kernel/genapic_64.c
+++ b/arch/x86/kernel/genapic_64.c
@@ -35,8 +35,10 @@ static struct genapic *apic_probe[] __initdata = {
 #ifdef CONFIG_X86_UV
         &apic_x2apic_uv_x,
 #endif
+#ifdef CONFIG_X86_X2APIC
         &apic_x2apic_phys,
         &apic_x2apic_cluster,
+#endif
         &apic_physflat,
         NULL,
 };
@@ -46,10 +48,12 @@ static struct genapic *apic_probe[] __initdata = {
  */
 void __init default_setup_apic_routing(void)
 {
+#ifdef CONFIG_X86_X2APIC
         if (apic == &apic_x2apic_phys || apic == &apic_x2apic_cluster) {
                 if (!intr_remapping_enabled)
                         apic = &apic_flat;
         }
+#endif
 
         if (apic == &apic_flat) {
                 if (max_physical_apicid >= 8)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 8fce6c71451..43d964411c0 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -836,8 +836,7 @@ void __init setup_arch(char **cmdline_p)
 #else
         num_physpages = max_pfn;
 
-        if (cpu_has_x2apic)
-                check_x2apic();
+        check_x2apic();
 
         /* How many end-of-memory variables you have, grandma! */
         /* need this before calling reserve_initrd */
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 10834954e30..b5f2b698973 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1128,8 +1128,8 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
         current_thread_info()->cpu = 0;  /* needed? */
         set_cpu_sibling_map(0);
 
-#ifdef CONFIG_X86_64
         enable_IR_x2apic();
+#ifdef CONFIG_X86_64
         default_setup_apic_routing();
 #endif