text: // SPDX-License-Identifier: GPL-2.0
  /*
   * NOOP APIC driver.
   *
   * Does almost nothing and should be substituted by a real apic driver via
   * probe routine.
   *
   * Though in case if apic is disabled (for some reason) we try
   * to not uglify the caller's code and allow to call (some) apic routines
   * like self-ipi, etc...
   */
  #include <linux/cpumask.h>
  #include <linux/thread_info.h>
  
  #include <asm/apic.h>
  
  static void noop_init_apic_ldr(void) { }
  static void noop_send_IPI(int cpu, int vector) { }
  static void noop_send_IPI_mask(const struct cpumask *cpumask, int vector) { }
  static void noop_send_IPI_mask_allbutself(const struct cpumask *cpumask, int vector) { }
  static void noop_send_IPI_allbutself(int vector) { }
  static void noop_send_IPI_all(int vector) { }
  static void noop_send_IPI_self(int vector) { }
  static void noop_apic_wait_icr_idle(void) { }
  static void noop_apic_icr_write(u32 low, u32 id) { }
  
  static int noop_wakeup_secondary_cpu(int apicid, unsigned long start_eip)
  {
  	return -1;
  }
  
  static u32 noop_safe_apic_wait_icr_idle(void)
  {
  	return 0;
  }
  
  static u64 noop_apic_icr_read(void)
  {
  	return 0;
  }
  
  static int noop_phys_pkg_id(int cpuid_apic, int index_msb)
  {
  	return 0;
  }
  
  static unsigned int noop_get_apic_id(unsigned long x)
  {
  	return 0;
  }
  
  static int noop_probe(void)
  {
  	/*
  	 * NOOP apic should not ever be
  	 * enabled via probe routine
  	 */
  	return 0;
  }
  
  static int noop_apic_id_registered(void)
  {
  	/*
  	 * if we would be really "pedantic"
  	 * we should pass read_apic_id() here
  	 * but since NOOP suppose APIC ID = 0
  	 * lets save a few cycles
  	 */
  	return physid_isset(0, phys_cpu_present_map);
  }
  
  static u32 noop_apic_read(u32 reg)
  {
  	WARN_ON_ONCE(boot_cpu_has(X86_FEATURE_APIC) && !disable_apic);
  	return 0;
  }
  
  static void noop_apic_write(u32 reg, u32 v)
  {
  	WARN_ON_ONCE(boot_cpu_has(X86_FEATURE_APIC) && !disable_apic);
  }
  
  #ifdef CONFIG_X86_32
  static int noop_x86_32_early_logical_apicid(int cpu)
  {
  	return BAD_APICID;
  }
  #endif
  
  struct apic apic_noop __ro_after_init = {
  	.name				= "noop",
  	.probe				= noop_probe,
  	.acpi_madt_oem_check		= NULL,
  
  	.apic_id_valid			= default_apic_id_valid,
  	.apic_id_registered		= noop_apic_id_registered,
  
  	.irq_delivery_mode		= dest_Fixed,
  	/* logical delivery broadcast to all CPUs: */
  	.irq_dest_mode			= 1,
  
  	.disable_esr			= 0,
  	.dest_logical			= APIC_DEST_LOGICAL,
  	.check_apicid_used		= default_check_apicid_used,
  
  	.init_apic_ldr			= noop_init_apic_ldr,
  
  	.ioapic_phys_id_map		= default_ioapic_phys_id_map,
  	.setup_apic_routing		= NULL,
  
  	.cpu_present_to_apicid		= default_cpu_present_to_apicid,
  	.apicid_to_cpu_present		= physid_set_mask_of_physid,
  
  	.check_phys_apicid_present	= default_check_phys_apicid_present,
  
  	.phys_pkg_id			= noop_phys_pkg_id,
  
  	.get_apic_id			= noop_get_apic_id,
  	.set_apic_id			= NULL,
  
  	.calc_dest_apicid		= apic_flat_calc_apicid,
  
  	.send_IPI			= noop_send_IPI,
  	.send_IPI_mask			= noop_send_IPI_mask,
  	.send_IPI_mask_allbutself	= noop_send_IPI_mask_allbutself,
  	.send_IPI_allbutself		= noop_send_IPI_allbutself,
  	.send_IPI_all			= noop_send_IPI_all,
  	.send_IPI_self			= noop_send_IPI_self,
  
  	.wakeup_secondary_cpu		= noop_wakeup_secondary_cpu,
  
  	.inquire_remote_apic		= NULL,
  
  	.read				= noop_apic_read,
  	.write				= noop_apic_write,
  	.eoi_write			= noop_apic_write,
  	.icr_read			= noop_apic_icr_read,
  	.icr_write			= noop_apic_icr_write,
  	.wait_icr_idle			= noop_apic_wait_icr_idle,
  	.safe_wait_icr_idle		= noop_safe_apic_wait_icr_idle,
  
  #ifdef CONFIG_X86_32
  	.x86_32_early_logical_apicid	= noop_x86_32_early_logical_apicid,
  #endif
  };
  