[patch 35/53] x86/cpu/topology: Sanitize the APIC admission logic

Thomas Gleixner
2023-08-07T13:54:54Z

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>
---
arch/x86/kernel/cpu/topology.c | 160 +++++++++++++++++-------------------
1 file changed, 78 insertions(+), 82 deletions(-)

--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -30,8 +30,10 @@ 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,
};

/*
@@ -78,78 +80,6 @@ early_initcall(smp_init_primary_thread_m
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;

/*
@@ -217,6 +147,43 @@ static int __initdata setup_possible_cpu
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_assign_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
@@ -229,17 +196,41 @@ void __init topology_register_apic(u32 a

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++;
+ /* CPU numbers exhausted? */
+ if (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;
}

- cpu = generic_processor_info(apic_id);
- if (cpu >= 0)
- early_per_cpu(x86_cpu_to_acpiid, cpu) = acpi_id;
+ 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;
+ }
+
+ if (present) {
+ /*
+ * Prevent double registration, which 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 (test_and_set_bit(apic_id, phys_cpu_present_map))
+ return;
+
+ if (apic_id == topo_info.boot_cpu_apic_id)
+ cpu = 0;
+ else
+ cpu = topo_assign_cpunr(apic_id);
+ topo_set_cpuids(cpu, apic_id, acpi_id);
+ } else {
+ topo_info.nr_disabled_cpus++;
+ }
}

/**
@@ -250,8 +241,10 @@ void __init topology_register_apic(u32 a
*/
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
@@ -269,10 +262,13 @@ int topology_hotplug_apic(u32 apic_id, u

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;
}