Revert "x86/apic: Remove init_bsp_APIC()"

This reverts commit b371ae0d. 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

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);

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)
 {

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++)