Revert "x86/apic: Remove init_bsp_APIC()"

This reverts commit b371ae0d4a194b178817b0edfb6a7395c7aec37a. It causes
boot hangs on old P3/P4 systems when the local APIC is enforced in UP mode.

Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dou Liyang <douly.fnst@cn.fujitsu.com>
Cc: yinghai@kernel.org
Cc: bhe@redhat.com
Link: https://lkml.kernel.org/r/20171128145350.21560-1-ville.syrjala@linux.intel.com

3 files changed, 53 insertions, 0 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index a9e57f08bfa6..98722773391d 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -136,6 +136,7 @@ extern void disconnect_bsp_APIC(int virt_wire_setup);
 extern void disable_local_APIC(void);
 extern void lapic_shutdown(void);
 extern void sync_Arb_IDs(void);
+extern void init_bsp_APIC(void);
 extern void apic_intr_mode_init(void);
 extern void setup_local_APIC(void);
 extern void init_apic_mappings(void);
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 880441f24146..25ddf02598d2 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1286,6 +1286,55 @@ static int __init apic_intr_mode_select(void)
         return APIC_SYMMETRIC_IO;
 }
 
+/*
+ * An initial setup of the virtual wire mode.
+ */
+void __init init_bsp_APIC(void)
+{
+        unsigned int value;
+
+        /*
+         * Don't do the setup now if we have a SMP BIOS as the
+         * through-I/O-APIC virtual wire mode might be active.
+         */
+        if (smp_found_config || !boot_cpu_has(X86_FEATURE_APIC))
+                return;
+
+        /*
+         * Do not trust the local APIC being empty at bootup.
+         */
+        clear_local_APIC();
+
+        /*
+         * Enable APIC.
+         */
+        value = apic_read(APIC_SPIV);
+        value &= ~APIC_VECTOR_MASK;
+        value |= APIC_SPIV_APIC_ENABLED;
+
+#ifdef CONFIG_X86_32
+        /* This bit is reserved on P4/Xeon and should be cleared */
+        if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) &&
+            (boot_cpu_data.x86 == 15))
+                value &= ~APIC_SPIV_FOCUS_DISABLED;
+        else
+#endif
+                value |= APIC_SPIV_FOCUS_DISABLED;
+        value |= SPURIOUS_APIC_VECTOR;
+        apic_write(APIC_SPIV, value);
+
+        /*
+         * Set up the virtual wire mode.
+         */
+        apic_write(APIC_LVT0, APIC_DM_EXTINT);
+        value = APIC_DM_NMI;
+        if (!lapic_is_integrated())             /* 82489DX */
+                value |= APIC_LVT_LEVEL_TRIGGER;
+        if (apic_extnmi == APIC_EXTNMI_NONE)
+                value |= APIC_LVT_MASKED;
+        apic_write(APIC_LVT1, value);
+}
+
 /* Init the interrupt delivery mode for the BSP */
 void __init apic_intr_mode_init(void)
 {
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index 8da3e909e967..a539410c4ea9 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -61,6 +61,9 @@ void __init init_ISA_irqs(void)
         struct irq_chip *chip = legacy_pic->chip;
         int i;
 
+#if defined(CONFIG_X86_64) || defined(CONFIG_X86_LOCAL_APIC)
+        init_bsp_APIC();
+#endif
         legacy_pic->init(0);
 
         for (i = 0; i < nr_legacy_irqs(); i++)