[tip-bot2@linutronix.de:,[tip:,x86/urgent] x86/timer: Don't skip PIT setup when APIC is disabled or in legacy mode]

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 2ebc17d..be0b9cf 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -140,6 +140,7 @@  extern void apic_soft_disable(void);
 extern void lapic_shutdown(void);
 extern void sync_Arb_IDs(void);
 extern void init_bsp_APIC(void);
+extern void apic_intr_mode_select(void);
 extern void apic_intr_mode_init(void);
 extern void init_apic_mappings(void);
 void register_lapic_address(unsigned long address);
@@ -188,6 +189,7 @@  static inline void disable_local_APIC(void) { }
 # define setup_secondary_APIC_clock x86_init_noop
 static inline void lapic_update_tsc_freq(void) { }
 static inline void init_bsp_APIC(void) { }
+static inline void apic_intr_mode_select(void) { }
 static inline void apic_intr_mode_init(void) { }
 static inline void lapic_assign_system_vectors(void) { }
 static inline void lapic_assign_legacy_vector(unsigned int i, bool r) { }
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 1943585..96d9cd2 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -51,12 +51,14 @@  struct x86_init_resources {
  *				are set up.
  * @intr_init:			interrupt init code
  * @trap_init:			platform specific trap setup
+ * @intr_mode_select:		interrupt delivery mode selection
  * @intr_mode_init:		interrupt delivery mode setup
  */
 struct x86_init_irqs {
 	void (*pre_vector_init)(void);
 	void (*intr_init)(void);
 	void (*trap_init)(void);
+	void (*intr_mode_select)(void);
 	void (*intr_mode_init)(void);
 };
 
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 28446fa..4b0f911 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -830,8 +830,17 @@  bool __init apic_needs_pit(void)
 	if (!tsc_khz || !cpu_khz)
 		return true;
 
-	/* Is there an APIC at all? */
-	if (!boot_cpu_has(X86_FEATURE_APIC))
+	/* Is there an APIC at all or is it disabled? */
+	if (!boot_cpu_has(X86_FEATURE_APIC) || disable_apic)
+		return true;
+
+	/*
+	 * If interrupt delivery mode is legacy PIC or virtual wire without
+	 * configuration, the local APIC timer wont be set up. Make sure
+	 * that the PIT is initialized.
+	 */
+	if (apic_intr_mode == APIC_PIC ||
+	    apic_intr_mode == APIC_VIRTUAL_WIRE_NO_CONFIG)
 		return true;
 
 	/* Virt guests may lack ARAT, but still have DEADLINE */
@@ -1322,7 +1331,7 @@  void __init sync_Arb_IDs(void)
 
 enum apic_intr_mode_id apic_intr_mode __ro_after_init;
 
-static int __init apic_intr_mode_select(void)
+static int __init __apic_intr_mode_select(void)
 {
 	/* Check kernel option */
 	if (disable_apic) {
@@ -1384,6 +1393,12 @@  static int __init apic_intr_mode_select(void)
 	return APIC_SYMMETRIC_IO;
 }
 
+/* Select the interrupt delivery mode for the BSP */
+void __init apic_intr_mode_select(void)
+{
+	apic_intr_mode = __apic_intr_mode_select();
+}
+
 /*
  * An initial setup of the virtual wire mode.
  */
@@ -1440,8 +1455,6 @@  void __init apic_intr_mode_init(void)
 {
 	bool upmode = IS_ENABLED(CONFIG_UP_LATE_INIT);
 
-	apic_intr_mode = apic_intr_mode_select();
-
 	switch (apic_intr_mode) {
 	case APIC_PIC:
 		pr_info("APIC: Keep in PIC mode(8259)\n");
diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index 7ce29ce..d8673d8 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -91,10 +91,18 @@  void __init hpet_time_init(void)
 
 static __init void x86_late_time_init(void)
 {
+	/*
+	 * Before PIT/HPET init, select the interrupt mode. This is required
+	 * to make the decision whether PIT should be initialized correct.
+	 */
+	x86_init.irqs.intr_mode_select();
+
+	/* Setup the legacy timers */
 	x86_init.timers.timer_init();
+
 	/*
-	 * After PIT/HPET timers init, select and setup
-	 * the final interrupt mode for delivering IRQs.
+	 * After PIT/HPET timers init, set up the final interrupt mode for
+	 * delivering IRQs.
 	 */
 	x86_init.irqs.intr_mode_init();
 	tsc_init();
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index ce89430..9a89261 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -80,6 +80,7 @@  struct x86_init_ops x86_init __initdata = {
 		.pre_vector_init	= init_ISA_irqs,
 		.intr_init		= native_init_IRQ,
 		.trap_init		= x86_init_noop,
+		.intr_mode_select	= apic_intr_mode_select,
 		.intr_mode_init		= apic_intr_mode_init
 	},
 
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index ae4a41c..1f756ff 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1205,6 +1205,7 @@  asmlinkage __visible void __init xen_start_kernel(void)
 	x86_platform.get_nmi_reason = xen_get_nmi_reason;
 
 	x86_init.resources.memory_setup = xen_memory_setup;
+	x86_init.irqs.intr_mode_select	= x86_init_noop;
 	x86_init.irqs.intr_mode_init	= x86_init_noop;
 	x86_init.oem.arch_setup = xen_arch_setup;
 	x86_init.oem.banner = xen_banner;