x86/cpu/topology: Sanitize the APIC admission logic

Move the actually required content of generic_processor_id() into the call
sites and use common helper functions for them. This separates the early
boot registration and the ACPI hotplug mechanism completely which allows
further cleanups and improvements.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.230433953@linutronix.de

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index 815e3eeed41593d4691738f6d17d5a602d16a758..80625f4194de5fff2c4aa72e4fc4d1c07384df89 100644 (file)
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -30,8 +30,10 @@ static struct {
        unsigned int            nr_assigned_cpus;
        unsigned int            nr_disabled_cpus;
        unsigned int            nr_rejected_cpus;
+       u32                     boot_cpu_apic_id;
 } topo_info __read_mostly = {
        .nr_assigned_cpus       = 1,
+       .boot_cpu_apic_id       = BAD_APICID,
 };
 
 /*
@@ -83,78 +85,6 @@ early_initcall(smp_init_primary_thread_mask);
 static inline void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid) { }
 #endif
 
-static int topo_lookup_cpuid(u32 apic_id)
-{
-       int i;
-
-       /* CPU# to APICID mapping is persistent once it is established */
-       for (i = 0; i < topo_info.nr_assigned_cpus; i++) {
-               if (cpuid_to_apicid[i] == apic_id)
-                       return i;
-       }
-       return -ENODEV;
-}
-
-/*
- * Should use this API to allocate logical CPU IDs to keep nr_logical_cpuids
- * and cpuid_to_apicid[] synchronized.
- */
-static int allocate_logical_cpuid(u32 apic_id)
-{
-       int cpu = topo_lookup_cpuid(apic_id);
-
-       if (cpu >= 0)
-               return cpu;
-
-       return topo_info.nr_assigned_cpus++;
-}
-
-static void cpu_update_apic(unsigned int cpu, u32 apic_id)
-{
-#if defined(CONFIG_SMP) || defined(CONFIG_X86_64)
-       early_per_cpu(x86_cpu_to_apicid, cpu) = apic_id;
-#endif
-       cpuid_to_apicid[cpu] = apic_id;
-       set_cpu_possible(cpu, true);
-       set_bit(apic_id, phys_cpu_present_map);
-       set_cpu_present(cpu, true);
-
-       if (system_state != SYSTEM_BOOTING)
-               cpu_mark_primary_thread(cpu, apic_id);
-}
-
-static int generic_processor_info(int apicid)
-{
-       int cpu;
-
-       /* The boot CPU must be set before MADT/MPTABLE parsing happens */
-       if (cpuid_to_apicid[0] == BAD_APICID)
-               panic("Boot CPU APIC not registered yet\n");
-
-       if (apicid == boot_cpu_physical_apicid)
-               return 0;
-
-       if (disabled_cpu_apicid == apicid) {
-               int thiscpu = topo_info.nr_assigned_cpus + topo_info.nr_disabled_cpus;
-
-               pr_warn("APIC: Disabling requested cpu. Processor %d/0x%x ignored.\n",
-                       thiscpu, apicid);
-
-               topo_info.nr_rejected_cpus++;
-               return -ENODEV;
-       }
-
-       if (topo_info.nr_assigned_cpus >= nr_cpu_ids) {
-               pr_warn_once("APIC: CPU limit of %d reached. Ignoring further CPUs\n", nr_cpu_ids);
-               topo_info.nr_rejected_cpus++;
-               return -ENOSPC;
-       }
-
-       cpu = allocate_logical_cpuid(apicid);
-       cpu_update_apic(cpu, apicid);
-       return cpu;
-}
-
 static int __initdata setup_possible_cpus = -1;
 
 /*
@@ -222,6 +152,43 @@ __init void prefill_possible_map(void)
                set_cpu_possible(i, true);
 }
 
+static int topo_lookup_cpuid(u32 apic_id)
+{
+       int i;
+
+       /* CPU# to APICID mapping is persistent once it is established */
+       for (i = 0; i < topo_info.nr_assigned_cpus; i++) {
+               if (cpuid_to_apicid[i] == apic_id)
+                       return i;
+       }
+       return -ENODEV;
+}
+
+static int topo_get_cpunr(u32 apic_id)
+{
+       int cpu = topo_lookup_cpuid(apic_id);
+
+       if (cpu >= 0)
+               return cpu;
+
+       return topo_info.nr_assigned_cpus++;
+}
+
+static void topo_set_cpuids(unsigned int cpu, u32 apic_id, u32 acpi_id)
+{
+#if defined(CONFIG_SMP) || defined(CONFIG_X86_64)
+       early_per_cpu(x86_cpu_to_apicid, cpu) = apic_id;
+       early_per_cpu(x86_cpu_to_acpiid, cpu) = acpi_id;
+#endif
+       cpuid_to_apicid[cpu] = apic_id;
+
+       set_cpu_possible(cpu, true);
+       set_cpu_present(cpu, true);
+
+       if (system_state != SYSTEM_BOOTING)
+               cpu_mark_primary_thread(cpu, apic_id);
+}
+
 /**
  * topology_register_apic - Register an APIC in early topology maps
  * @apic_id:   The APIC ID to set up
@@ -234,17 +201,40 @@ void __init topology_register_apic(u32 apic_id, u32 acpi_id, bool present)
 
        if (apic_id >= MAX_LOCAL_APIC) {
                pr_err_once("APIC ID %x exceeds kernel limit of: %x\n", apic_id, MAX_LOCAL_APIC - 1);
+               topo_info.nr_rejected_cpus++;
                return;
        }
 
-       if (!present) {
-               topo_info.nr_disabled_cpus++;
+       if (disabled_cpu_apicid == apic_id) {
+               pr_info("Disabling CPU as requested via 'disable_cpu_apicid=0x%x'.\n", apic_id);
+               topo_info.nr_rejected_cpus++;
                return;
        }
 
-       cpu = generic_processor_info(apic_id);
-       if (cpu >= 0)
-               early_per_cpu(x86_cpu_to_acpiid, cpu) = acpi_id;
+       /* CPU numbers exhausted? */
+       if (apic_id != topo_info.boot_cpu_apic_id && topo_info.nr_assigned_cpus >= nr_cpu_ids) {
+               pr_warn_once("CPU limit of %d reached. Ignoring further CPUs\n", nr_cpu_ids);
+               topo_info.nr_rejected_cpus++;
+               return;
+       }
+
+       if (present) {
+               set_bit(apic_id, phys_cpu_present_map);
+
+               /*
+                * Double registration is valid in case of the boot CPU
+                * APIC because that is registered before the enumeration
+                * of the APICs via firmware parsers or VM guest
+                * mechanisms.
+                */
+               if (apic_id == topo_info.boot_cpu_apic_id)
+                       cpu = 0;
+               else
+                       cpu = topo_get_cpunr(apic_id);
+               topo_set_cpuids(cpu, apic_id, acpi_id);
+       } else {
+               topo_info.nr_disabled_cpus++;
+       }
 }
 
 /**
@@ -255,8 +245,10 @@ void __init topology_register_apic(u32 apic_id, u32 acpi_id, bool present)
  */
 void __init topology_register_boot_apic(u32 apic_id)
 {
-       cpuid_to_apicid[0] = apic_id;
-       cpu_update_apic(0, apic_id);
+       WARN_ON_ONCE(topo_info.boot_cpu_apic_id != BAD_APICID);
+
+       topo_info.boot_cpu_apic_id = apic_id;
+       topology_register_apic(apic_id, CPU_ACPIID_INVALID, true);
 }
 
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
@@ -274,10 +266,13 @@ int topology_hotplug_apic(u32 apic_id, u32 acpi_id)
 
        cpu = topo_lookup_cpuid(apic_id);
        if (cpu < 0) {
-               cpu = generic_processor_info(apic_id);
-               if (cpu >= 0)
-                       per_cpu(x86_cpu_to_acpiid, cpu) = acpi_id;
+               if (topo_info.nr_assigned_cpus >= nr_cpu_ids)
+                       return -ENOSPC;
+
+               cpu = topo_assign_cpunr(apic_id);
        }
+       set_bit(apic_id, phys_cpu_present_map);
+       topo_set_cpuids(cpu, apic_id, acpi_id);
        return cpu;
 }