3 files changed, 56 insertions, 40 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index bb7d47925847..586b7adb8e53 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -183,6 +183,10 @@ static inline int x2apic_enabled(void)
 }
 
 #define x2apic_supported()      (cpu_has_x2apic)
+static inline void x2apic_force_phys(void)
+{
+        x2apic_phys = 1;
+}
 #else
 static inline void check_x2apic(void)
 {
@@ -194,6 +198,9 @@ static inline int x2apic_enabled(void)
 {
         return 0;
 }
+static inline void x2apic_force_phys(void)
+{
+}
 
 #define x2apic_preenabled 0
 #define x2apic_supported()      0
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 0b021c56e822..de039fcdd053 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -49,6 +49,7 @@
 #include <asm/mtrr.h>
 #include <asm/smp.h>
 #include <asm/mce.h>
+#include <asm/kvm_para.h>
 
 unsigned int num_processors;
 
@@ -1361,52 +1362,76 @@ void enable_x2apic(void)
 }
 #endif /* CONFIG_X86_X2APIC */
 
-void __init enable_IR_x2apic(void)
+int __init enable_IR(void)
 {
 #ifdef CONFIG_INTR_REMAP
         int ret;
-        unsigned long flags;
-        struct IO_APIC_route_entry **ioapic_entries = NULL;
 
         ret = dmar_table_init();
         if (ret) {
                 pr_debug("dmar_table_init() failed with %d:\n", ret);
-                goto ir_failed;
+                return 0;
         }
 
         if (!intr_remapping_supported()) {
                 pr_debug("intr-remapping not supported\n");
-                goto ir_failed;
+                return 0;
         }
 
-
         if (!x2apic_preenabled && skip_ioapic_setup) {
                 pr_info("Skipped enabling intr-remap because of skipping "
                         "io-apic setup\n");
-                return;
+                return 0;
         }
 
+        if (enable_intr_remapping(x2apic_supported()))
+                return 0;
+
+        pr_info("Enabled Interrupt-remapping\n");
+
+        return 1;
+
+#endif
+        return 0;
+}
+
+void __init enable_IR_x2apic(void)
+{
+        unsigned long flags;
+        struct IO_APIC_route_entry **ioapic_entries = NULL;
+        int ret, x2apic_enabled = 0;
+
         ioapic_entries = alloc_ioapic_entries();
         if (!ioapic_entries) {
-                pr_info("Allocate ioapic_entries failed: %d\n", ret);
-                goto end;
+                pr_err("Allocate ioapic_entries failed\n");
+                goto out;
         }
 
         ret = save_IO_APIC_setup(ioapic_entries);
         if (ret) {
                 pr_info("Saving IO-APIC state failed: %d\n", ret);
-                goto end;
+                goto out;
         }
 
         local_irq_save(flags);
-        mask_IO_APIC_setup(ioapic_entries);
         mask_8259A();
+        mask_IO_APIC_setup(ioapic_entries);
 
-        ret = enable_intr_remapping(x2apic_supported());
-        if (ret)
-                goto end_restore;
+        ret = enable_IR();
+        if (!ret) {
+                /* IR is required if there is APIC ID > 255 even when running
+                 * under KVM
+                 */
+                if (max_physical_apicid > 255 || !kvm_para_available())
+                        goto nox2apic;
+                /*
+                 * without IR all CPUs can be addressed by IOAPIC/MSI
+                 * only in physical mode
+                 */
+                x2apic_force_phys();
+        }
 
-        pr_info("Enabled Interrupt-remapping\n");
+        x2apic_enabled = 1;
 
         if (x2apic_supported() && !x2apic_mode) {
                 x2apic_mode = 1;
@@ -1414,41 +1439,25 @@ void __init enable_IR_x2apic(void)
                 pr_info("Enabled x2apic\n");
         }
 
-end_restore:
-        if (ret)
-                /*
-                 * IR enabling failed
-                 */
+nox2apic:
+        if (!ret) /* IR enabling failed */
                 restore_IO_APIC_setup(ioapic_entries);
-
         unmask_8259A();
         local_irq_restore(flags);
 
-end:
+out:
         if (ioapic_entries)
                 free_ioapic_entries(ioapic_entries);
 
-        if (!ret)
+        if (x2apic_enabled)
                 return;
 
-ir_failed:
         if (x2apic_preenabled)
-                panic("x2apic enabled by bios. But IR enabling failed");
+                panic("x2apic: enabled by BIOS but kernel init failed.");
         else if (cpu_has_x2apic)
-                pr_info("Not enabling x2apic,Intr-remapping\n");
-#else
-        if (!cpu_has_x2apic)
-                return;
-
-        if (x2apic_preenabled)
-                panic("x2apic enabled prior OS handover,"
-                      " enable CONFIG_X86_X2APIC, CONFIG_INTR_REMAP");
-#endif
-
-        return;
+                pr_info("Not enabling x2apic, Intr-remapping init failed.\n");
 }
 
-
 #ifdef CONFIG_X86_64
 /*
  * Detect and enable local APICs on non-SMP boards.
diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index bc3e880f9b82..f3b1037076e4 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -50,11 +50,11 @@ static struct apic *apic_probe[] __initdata = {
 void __init default_setup_apic_routing(void)
 {
 #ifdef CONFIG_X86_X2APIC
-        if (x2apic_mode && (apic != &apic_x2apic_phys &&
+        if (x2apic_mode
 #ifdef CONFIG_X86_UV
-                       apic != &apic_x2apic_uv_x &&
+                       && apic != &apic_x2apic_uv_x
 #endif
-                       apic != &apic_x2apic_cluster)) {
+                       ) {
                 if (x2apic_phys)
                         apic = &apic_x2apic_phys;
                 else