text: // SPDX-License-Identifier: GPL-2.0
  
  #include <linux/cpumask.h>
  #include <linux/smp.h>
  #include <asm/io_apic.h>
  
  #include "local.h"
  
  DEFINE_STATIC_KEY_FALSE(apic_use_ipi_shorthand);
  
  #ifdef CONFIG_SMP
  static int apic_ipi_shorthand_off __ro_after_init;
  
  static __init int apic_ipi_shorthand(char *str)
  {
  	get_option(&str, &apic_ipi_shorthand_off);
  	return 1;
  }
  __setup("no_ipi_broadcast=", apic_ipi_shorthand);
  
  static int __init print_ipi_mode(void)
  {
  	pr_info("IPI shorthand broadcast: %s\n",
  		apic_ipi_shorthand_off ? "disabled" : "enabled");
  	return 0;
  }
  late_initcall(print_ipi_mode);
  
  void apic_smt_update(void)
  {
  	/*
  	 * Do not switch to broadcast mode if:
  	 * - Disabled on the command line
  	 * - Only a single CPU is online
  	 * - Not all present CPUs have been at least booted once
  	 *
  	 * The latter is important as the local APIC might be in some
  	 * random state and a broadcast might cause havoc. That's
  	 * especially true for NMI broadcasting.
  	 */
  	if (apic_ipi_shorthand_off || num_online_cpus() == 1 ||
  	    !cpumask_equal(cpu_present_mask, &cpus_booted_once_mask)) {
  		static_branch_disable(&apic_use_ipi_shorthand);
  	} else {
  		static_branch_enable(&apic_use_ipi_shorthand);
  	}
  }
  
  void apic_send_IPI_allbutself(unsigned int vector)
  {
  	if (num_online_cpus() < 2)
  		return;
  
  	if (static_branch_likely(&apic_use_ipi_shorthand))
  		apic->send_IPI_allbutself(vector);
  	else
  		apic->send_IPI_mask_allbutself(cpu_online_mask, vector);
  }
  
  /*
   * Send a 'reschedule' IPI to another CPU. It goes straight through and
   * wastes no time serializing anything. Worst case is that we lose a
   * reschedule ...
   */
  void native_smp_send_reschedule(int cpu)
  {
  	if (unlikely(cpu_is_offline(cpu))) {
  		WARN(1, "sched: Unexpected reschedule of offline CPU#%d!\n", cpu);
  		return;
  	}
  	apic->send_IPI(cpu, RESCHEDULE_VECTOR);
  }
  
  void native_send_call_func_single_ipi(int cpu)
  {
  	apic->send_IPI(cpu, CALL_FUNCTION_SINGLE_VECTOR);
  }
  
  void native_send_call_func_ipi(const struct cpumask *mask)
  {
  	if (static_branch_likely(&apic_use_ipi_shorthand)) {
  		unsigned int cpu = smp_processor_id();
  
  		if (!cpumask_or_equal(mask, cpumask_of(cpu), cpu_online_mask))
  			goto sendmask;
  
  		if (cpumask_test_cpu(cpu, mask))
  			apic->send_IPI_all(CALL_FUNCTION_VECTOR);
  		else if (num_online_cpus() > 1)
  			apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR);
  		return;
  	}
  
  sendmask:
  	apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
  }
  
  #endif /* CONFIG_SMP */
  
  static inline int __prepare_ICR2(unsigned int mask)
  {
  	return SET_APIC_DEST_FIELD(mask);
  }
  
  static inline void __xapic_wait_icr_idle(void)
  {
  	while (native_apic_mem_read(APIC_ICR) & APIC_ICR_BUSY)
  		cpu_relax();
  }
  
  void __default_send_IPI_shortcut(unsigned int shortcut, int vector)
  {
  	/*
  	 * Subtle. In the case of the 'never do double writes' workaround
  	 * we have to lock out interrupts to be safe.  As we don't care
  	 * of the value read we use an atomic rmw access to avoid costly
  	 * cli/sti.  Otherwise we use an even cheaper single atomic write
  	 * to the APIC.
  	 */
  	unsigned int cfg;
  
  	/*
  	 * Wait for idle.
  	 */
  	if (unlikely(vector == NMI_VECTOR))
  		safe_apic_wait_icr_idle();
  	else
  		__xapic_wait_icr_idle();
  
  	/*
  	 * No need to touch the target chip field. Also the destination
  	 * mode is ignored when a shorthand is used.
  	 */
  	cfg = __prepare_ICR(shortcut, vector, 0);
  
  	/*
  	 * Send the IPI. The write to APIC_ICR fires this off.
  	 */
  	native_apic_mem_write(APIC_ICR, cfg);
  }
  
  /*
   * This is used to send an IPI with no shorthand notation (the destination is
   * specified in bits 56 to 63 of the ICR).
   */
  void __default_send_IPI_dest_field(unsigned int mask, int vector, unsigned int dest)
  {
  	unsigned long cfg;
  
  	/*
  	 * Wait for idle.
  	 */
  	if (unlikely(vector == NMI_VECTOR))
  		safe_apic_wait_icr_idle();
  	else
  		__xapic_wait_icr_idle();
  
  	/*
  	 * prepare target chip field
  	 */
  	cfg = __prepare_ICR2(mask);
  	native_apic_mem_write(APIC_ICR2, cfg);
  
  	/*
  	 * program the ICR
  	 */
  	cfg = __prepare_ICR(0, vector, dest);
  
  	/*
  	 * Send the IPI. The write to APIC_ICR fires this off.
  	 */
  	native_apic_mem_write(APIC_ICR, cfg);
  }
  
  void default_send_IPI_single_phys(int cpu, int vector)
  {
  	unsigned long flags;
  
  	local_irq_save(flags);
  	__default_send_IPI_dest_field(per_cpu(x86_cpu_to_apicid, cpu),
  				      vector, APIC_DEST_PHYSICAL);
  	local_irq_restore(flags);
  }
  
  void default_send_IPI_mask_sequence_phys(const struct cpumask *mask, int vector)
  {
  	unsigned long query_cpu;
  	unsigned long flags;
  
  	/*
  	 * Hack. The clustered APIC addressing mode doesn't allow us to send
  	 * to an arbitrary mask, so I do a unicast to each CPU instead.
  	 * - mbligh
  	 */
  	local_irq_save(flags);
  	for_each_cpu(query_cpu, mask) {
  		__default_send_IPI_dest_field(per_cpu(x86_cpu_to_apicid,
  				query_cpu), vector, APIC_DEST_PHYSICAL);
  	}
  	local_irq_restore(flags);
  }
  
  void default_send_IPI_mask_allbutself_phys(const struct cpumask *mask,
  						 int vector)
  {
  	unsigned int this_cpu = smp_processor_id();
  	unsigned int query_cpu;
  	unsigned long flags;
  
  	/* See Hack comment above */
  
  	local_irq_save(flags);
  	for_each_cpu(query_cpu, mask) {
  		if (query_cpu == this_cpu)
  			continue;
  		__default_send_IPI_dest_field(per_cpu(x86_cpu_to_apicid,
  				 query_cpu), vector, APIC_DEST_PHYSICAL);
  	}
  	local_irq_restore(flags);
  }
  
  /*
   * Helper function for APICs which insist on cpumasks
   */
  void default_send_IPI_single(int cpu, int vector)
  {
  	apic->send_IPI_mask(cpumask_of(cpu), vector);
  }
  
  void default_send_IPI_allbutself(int vector)
  {
  	__default_send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
  }
  
  void default_send_IPI_all(int vector)
  {
  	__default_send_IPI_shortcut(APIC_DEST_ALLINC, vector);
  }
  
  void default_send_IPI_self(int vector)
  {
  	__default_send_IPI_shortcut(APIC_DEST_SELF, vector);
  }
  
  #ifdef CONFIG_X86_32
  
  void default_send_IPI_mask_sequence_logical(const struct cpumask *mask,
  						 int vector)
  {
  	unsigned long flags;
  	unsigned int query_cpu;
  
  	/*
  	 * Hack. The clustered APIC addressing mode doesn't allow us to send
  	 * to an arbitrary mask, so I do a unicasts to each CPU instead. This
  	 * should be modified to do 1 message per cluster ID - mbligh
  	 */
  
  	local_irq_save(flags);
  	for_each_cpu(query_cpu, mask)
  		__default_send_IPI_dest_field(
  			early_per_cpu(x86_cpu_to_logical_apicid, query_cpu),
  			vector, APIC_DEST_LOGICAL);
  	local_irq_restore(flags);
  }
  
  void default_send_IPI_mask_allbutself_logical(const struct cpumask *mask,
  						 int vector)
  {
  	unsigned long flags;
  	unsigned int query_cpu;
  	unsigned int this_cpu = smp_processor_id();
  
  	/* See Hack comment above */
  
  	local_irq_save(flags);
  	for_each_cpu(query_cpu, mask) {
  		if (query_cpu == this_cpu)
  			continue;
  		__default_send_IPI_dest_field(
  			early_per_cpu(x86_cpu_to_logical_apicid, query_cpu),
  			vector, APIC_DEST_LOGICAL);
  		}
  	local_irq_restore(flags);
  }
  
  /*
   * This is only used on smaller machines.
   */
  void default_send_IPI_mask_logical(const struct cpumask *cpumask, int vector)
  {
  	unsigned long mask = cpumask_bits(cpumask)[0];
  	unsigned long flags;
  
  	if (!mask)
  		return;
  
  	local_irq_save(flags);
  	WARN_ON(mask & ~cpumask_bits(cpu_online_mask)[0]);
  	__default_send_IPI_dest_field(mask, vector, APIC_DEST_LOGICAL);
  	local_irq_restore(flags);
  }
  
  /* must come after the send_IPI functions above for inlining */
  static int convert_apicid_to_cpu(int apic_id)
  {
  	int i;
  
  	for_each_possible_cpu(i) {
  		if (per_cpu(x86_cpu_to_apicid, i) == apic_id)
  			return i;
  	}
  	return -1;
  }
  
  int safe_smp_processor_id(void)
  {
  	int apicid, cpuid;
  
  	if (!boot_cpu_has(X86_FEATURE_APIC))
  		return 0;
  
  	apicid = hard_smp_processor_id();
  	if (apicid == BAD_APICID)
  		return 0;
  
  	cpuid = convert_apicid_to_cpu(apicid);
  
  	return cpuid >= 0 ? cpuid : 0;
  }
  #endif
  