x86/smpboot: Sanitize uniprocessor init

The UP related setups for local apic are mangled into smp_sanity_check().

That results in duplicate calls to disable_smp() and makes the code
hard to follow. Let smp_sanity_check() return dedicated values for the
various exit reasons and handle them at the call site.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/20150115211703.987833932@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 26 insertions, 11 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index d53870928824..fe8783d500c2 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -990,6 +990,8 @@ void arch_disable_smp_support(void)
  */
 static __init void disable_smp(void)
 {
+        pr_info("SMP disabled\n");
+
         disable_ioapic_support();
 
         init_cpu_present(cpumask_of(0));
@@ -1003,6 +1005,13 @@ static __init void disable_smp(void)
         cpumask_set_cpu(0, cpu_core_mask(0));
 }
 
+enum {
+        SMP_OK,
+        SMP_NO_CONFIG,
+        SMP_NO_APIC,
+        SMP_FORCE_UP,
+};
+
 /*
  * Various sanity checks.
  */
@@ -1050,10 +1059,7 @@ static int __init smp_sanity_check(unsigned max_cpus)
         if (!smp_found_config && !acpi_lapic) {
                 preempt_enable();
                 pr_notice("SMP motherboard not detected\n");
-                disable_smp();
-                if (APIC_init_uniprocessor())
-                        pr_notice("Local APIC not detected. Using dummy APIC emulation.\n");
-                return -1;
+                return SMP_NO_CONFIG;
         }
 
         /*
@@ -1077,7 +1083,7 @@ static int __init smp_sanity_check(unsigned max_cpus)
                                 boot_cpu_physical_apicid);
                         pr_err("... forcing use of dummy APIC emulation (tell your hw vendor)\n");
                 }
-                return -1;
+                return SMP_NO_APIC;
         }
 
         verify_local_APIC();
@@ -1087,12 +1093,10 @@ static int __init smp_sanity_check(unsigned max_cpus)
          */
         if (!max_cpus) {
                 pr_info("SMP mode deactivated\n");
-                disable_ioapic_support();
-                apic_bsp_setup();
-                return -1;
+                return SMP_FORCE_UP;
         }
 
-        return 0;
+        return SMP_OK;
 }
 
 static void __init smp_cpu_index_default(void)
@@ -1132,10 +1136,21 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
         }
         set_cpu_sibling_map(0);
 
-        if (smp_sanity_check(max_cpus) < 0) {
-                pr_info("SMP disabled\n");
+        switch (smp_sanity_check(max_cpus)) {
+        case SMP_NO_CONFIG:
                 disable_smp();
+                if (APIC_init_uniprocessor())
+                        pr_notice("Local APIC not detected. Using dummy APIC emulation.\n");
+                return;
+        case SMP_NO_APIC:
+                disable_smp();
+                return;
+        case SMP_FORCE_UP:
+                disable_smp();
+                apic_bsp_setup();
                 return;
+        case SMP_OK:
+                break;
         }
 
         default_setup_apic_routing();