Merging upstream version 6.9.7.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 518 insertions, 114 deletions

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index dc13670356..621a151ccf 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -1,167 +1,571 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
- * Check for extended topology enumeration cpuid leaf 0xb and if it
- * exists, use it for populating initial_apicid and cpu topology
- * detection.
+ * CPU/APIC topology
+ *
+ * The APIC IDs describe the system topology in multiple domain levels.
+ * The CPUID topology parser provides the information which part of the
+ * APIC ID is associated to the individual levels:
+ *
+ * [PACKAGE][DIEGRP][DIE][TILE][MODULE][CORE][THREAD]
+ *
+ * The root space contains the package (socket) IDs.
+ *
+ * Not enumerated levels consume 0 bits space, but conceptually they are
+ * always represented. If e.g. only CORE and THREAD levels are enumerated
+ * then the DIE, MODULE and TILE have the same physical ID as the PACKAGE.
+ *
+ * If SMT is not supported, then the THREAD domain is still used. It then
+ * has the same physical ID as the CORE domain and is the only child of
+ * the core domain.
+ *
+ * This allows a unified view on the system independent of the enumerated
+ * domain levels without requiring any conditionals in the code.
  */
-
+#define pr_fmt(fmt) "CPU topo: " fmt
 #include <linux/cpu.h>
+
+#include <xen/xen.h>
+
 #include <asm/apic.h>
-#include <asm/memtype.h>
-#include <asm/processor.h>
+#include <asm/hypervisor.h>
+#include <asm/io_apic.h>
+#include <asm/mpspec.h>
+#include <asm/smp.h>
 
 #include "cpu.h"
 
-/* leaf 0xb SMT level */
-#define SMT_LEVEL	0
+/*
+ * Map cpu index to physical APIC ID
+ */
+DEFINE_EARLY_PER_CPU_READ_MOSTLY(u32, x86_cpu_to_apicid, BAD_APICID);
+DEFINE_EARLY_PER_CPU_READ_MOSTLY(u32, x86_cpu_to_acpiid, CPU_ACPIID_INVALID);
+EXPORT_EARLY_PER_CPU_SYMBOL(x86_cpu_to_apicid);
+EXPORT_EARLY_PER_CPU_SYMBOL(x86_cpu_to_acpiid);
 
-/* extended topology sub-leaf types */
-#define INVALID_TYPE	0
-#define SMT_TYPE	1
-#define CORE_TYPE	2
-#define DIE_TYPE	5
+/* Bitmap of physically present CPUs. */
+DECLARE_BITMAP(phys_cpu_present_map, MAX_LOCAL_APIC) __read_mostly;
 
-#define LEAFB_SUBTYPE(ecx)		(((ecx) >> 8) & 0xff)
-#define BITS_SHIFT_NEXT_LEVEL(eax)	((eax) & 0x1f)
-#define LEVEL_MAX_SIBLINGS(ebx)		((ebx) & 0xffff)
+/* Used for CPU number allocation and parallel CPU bringup */
+u32 cpuid_to_apicid[] __ro_after_init = { [0 ... NR_CPUS - 1] = BAD_APICID, };
 
-unsigned int __max_die_per_package __read_mostly = 1;
-EXPORT_SYMBOL(__max_die_per_package);
+/* Bitmaps to mark registered APICs at each topology domain */
+static struct { DECLARE_BITMAP(map, MAX_LOCAL_APIC); } apic_maps[TOPO_MAX_DOMAIN] __ro_after_init;
 
-#ifdef CONFIG_SMP
 /*
- * Check if given CPUID extended topology "leaf" is implemented
+ * Keep track of assigned, disabled and rejected CPUs. Present assigned
+ * with 1 as CPU #0 is reserved for the boot CPU.
  */
-static int check_extended_topology_leaf(int leaf)
-{
-	unsigned int eax, ebx, ecx, edx;
+static struct {
+	unsigned int		nr_assigned_cpus;
+	unsigned int		nr_disabled_cpus;
+	unsigned int		nr_rejected_cpus;
+	u32			boot_cpu_apic_id;
+	u32			real_bsp_apic_id;
+} topo_info __ro_after_init = {
+	.nr_assigned_cpus	= 1,
+	.boot_cpu_apic_id	= BAD_APICID,
+	.real_bsp_apic_id	= BAD_APICID,
+};
 
-	cpuid_count(leaf, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
+#define domain_weight(_dom)	bitmap_weight(apic_maps[_dom].map, MAX_LOCAL_APIC)
 
-	if (ebx == 0 || (LEAFB_SUBTYPE(ecx) != SMT_TYPE))
-		return -1;
+bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
+{
+	return phys_id == (u64)cpuid_to_apicid[cpu];
+}
 
-	return 0;
+#ifdef CONFIG_SMP
+static void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid)
+{
+	if (!(apicid & (__max_threads_per_core - 1)))
+		cpumask_set_cpu(cpu, &__cpu_primary_thread_mask);
 }
+#else
+static inline void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid) { }
+#endif
+
 /*
- * Return best CPUID Extended Topology Leaf supported
+ * Convert the APIC ID to a domain level ID by masking out the low bits
+ * below the domain level @dom.
  */
-static int detect_extended_topology_leaf(struct cpuinfo_x86 *c)
+static inline u32 topo_apicid(u32 apicid, enum x86_topology_domains dom)
 {
-	if (c->cpuid_level >= 0x1f) {
-		if (check_extended_topology_leaf(0x1f) == 0)
-			return 0x1f;
-	}
+	if (dom == TOPO_SMT_DOMAIN)
+		return apicid;
+	return apicid & (UINT_MAX << x86_topo_system.dom_shifts[dom - 1]);
+}
 
-	if (c->cpuid_level >= 0xb) {
-		if (check_extended_topology_leaf(0xb) == 0)
-			return 0xb;
-	}
+static int topo_lookup_cpuid(u32 apic_id)
+{
+	int i;
 
-	return -1;
+	/* 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;
 }
-#endif
 
-int detect_extended_topology_early(struct cpuinfo_x86 *c)
+static __init int topo_get_cpunr(u32 apic_id)
 {
-#ifdef CONFIG_SMP
-	unsigned int eax, ebx, ecx, edx;
-	int leaf;
+	int cpu = topo_lookup_cpuid(apic_id);
 
-	leaf = detect_extended_topology_leaf(c);
-	if (leaf < 0)
-		return -1;
+	if (cpu >= 0)
+		return cpu;
 
-	set_cpu_cap(c, X86_FEATURE_XTOPOLOGY);
+	return topo_info.nr_assigned_cpus++;
+}
 
-	cpuid_count(leaf, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
-	/*
-	 * initial apic id, which also represents 32-bit extended x2apic id.
-	 */
-	c->topo.initial_apicid = edx;
-	smp_num_siblings = max_t(int, smp_num_siblings, LEVEL_MAX_SIBLINGS(ebx));
+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
-	return 0;
+	set_cpu_present(cpu, true);
 }
 
-/*
- * Check for extended topology enumeration cpuid leaf, and if it
- * exists, use it for populating initial_apicid and cpu topology
- * detection.
- */
-int detect_extended_topology(struct cpuinfo_x86 *c)
+static __init bool check_for_real_bsp(u32 apic_id)
 {
-#ifdef CONFIG_SMP
-	unsigned int eax, ebx, ecx, edx, sub_index;
-	unsigned int ht_mask_width, core_plus_mask_width, die_plus_mask_width;
-	unsigned int core_select_mask, core_level_siblings;
-	unsigned int die_select_mask, die_level_siblings;
-	unsigned int pkg_mask_width;
-	bool die_level_present = false;
-	int leaf;
-
-	leaf = detect_extended_topology_leaf(c);
-	if (leaf < 0)
-		return -1;
+	bool is_bsp = false, has_apic_base = boot_cpu_data.x86 >= 6;
+	u64 msr;
 
 	/*
-	 * Populate HT related information from sub-leaf level 0.
+	 * There is no real good way to detect whether this a kdump()
+	 * kernel, but except on the Voyager SMP monstrosity which is not
+	 * longer supported, the real BSP APIC ID is the first one which is
+	 * enumerated by firmware. That allows to detect whether the boot
+	 * CPU is the real BSP. If it is not, then do not register the APIC
+	 * because sending INIT to the real BSP would reset the whole
+	 * system.
+	 *
+	 * The first APIC ID which is enumerated by firmware is detectable
+	 * because the boot CPU APIC ID is registered before that without
+	 * invoking this code.
 	 */
-	cpuid_count(leaf, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
-	c->topo.initial_apicid = edx;
-	core_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
-	smp_num_siblings = max_t(int, smp_num_siblings, LEVEL_MAX_SIBLINGS(ebx));
-	core_plus_mask_width = ht_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
-	die_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
-	pkg_mask_width = die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
-
-	sub_index = 1;
-	while (true) {
-		cpuid_count(leaf, sub_index, &eax, &ebx, &ecx, &edx);
+	if (topo_info.real_bsp_apic_id != BAD_APICID)
+		return false;
 
+	/*
+	 * Check whether the enumeration order is broken by evaluating the
+	 * BSP bit in the APICBASE MSR. If the CPU does not have the
+	 * APICBASE MSR then the BSP detection is not possible and the
+	 * kernel must rely on the firmware enumeration order.
+	 */
+	if (has_apic_base) {
+		rdmsrl(MSR_IA32_APICBASE, msr);
+		is_bsp = !!(msr & MSR_IA32_APICBASE_BSP);
+	}
+
+	if (apic_id == topo_info.boot_cpu_apic_id) {
 		/*
-		 * Check for the Core type in the implemented sub leaves.
+		 * If the boot CPU has the APIC BSP bit set then the
+		 * firmware enumeration is agreeing. If the CPU does not
+		 * have the APICBASE MSR then the only choice is to trust
+		 * the enumeration order.
 		 */
-		if (LEAFB_SUBTYPE(ecx) == CORE_TYPE) {
-			core_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
-			core_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
-			die_level_siblings = core_level_siblings;
-			die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
-		}
-		if (LEAFB_SUBTYPE(ecx) == DIE_TYPE) {
-			die_level_present = true;
-			die_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
-			die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
+		if (is_bsp || !has_apic_base) {
+			topo_info.real_bsp_apic_id = apic_id;
+			return false;
 		}
+		/*
+		 * If the boot APIC is enumerated first, but the APICBASE
+		 * MSR does not have the BSP bit set, then there is no way
+		 * to discover the real BSP here. Assume a crash kernel and
+		 * limit the number of CPUs to 1 as an INIT to the real BSP
+		 * would reset the machine.
+		 */
+		pr_warn("Enumerated BSP APIC %x is not marked in APICBASE MSR\n", apic_id);
+		pr_warn("Assuming crash kernel. Limiting to one CPU to prevent machine INIT\n");
+		set_nr_cpu_ids(1);
+		goto fwbug;
+	}
 
-		if (LEAFB_SUBTYPE(ecx) != INVALID_TYPE)
-			pkg_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
-		else
-			break;
+	pr_warn("Boot CPU APIC ID not the first enumerated APIC ID: %x != %x\n",
+		topo_info.boot_cpu_apic_id, apic_id);
 
-		sub_index++;
+	if (is_bsp) {
+		/*
+		 * The boot CPU has the APIC BSP bit set. Use it and complain
+		 * about the broken firmware enumeration.
+		 */
+		topo_info.real_bsp_apic_id = topo_info.boot_cpu_apic_id;
+		goto fwbug;
 	}
 
-	core_select_mask = (~(-1 << pkg_mask_width)) >> ht_mask_width;
-	die_select_mask = (~(-1 << die_plus_mask_width)) >>
-				core_plus_mask_width;
+	pr_warn("Crash kernel detected. Disabling real BSP to prevent machine INIT\n");
+
+	topo_info.real_bsp_apic_id = apic_id;
+	return true;
+
+fwbug:
+	pr_warn(FW_BUG "APIC enumeration order not specification compliant\n");
+	return false;
+}
+
+static unsigned int topo_unit_count(u32 lvlid, enum x86_topology_domains at_level,
+				    unsigned long *map)
+{
+	unsigned int id, end, cnt = 0;
+
+	/* Calculate the exclusive end */
+	end = lvlid + (1U << x86_topo_system.dom_shifts[at_level]);
+
+	/* Unfortunately there is no bitmap_weight_range() */
+	for (id = find_next_bit(map, end, lvlid); id < end; id = find_next_bit(map, end, ++id))
+		cnt++;
+	return cnt;
+}
+
+static __init void topo_register_apic(u32 apic_id, u32 acpi_id, bool present)
+{
+	int cpu, dom;
+
+	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);
+
+		cpuid_to_apicid[cpu] = apic_id;
+		topo_set_cpuids(cpu, apic_id, acpi_id);
+	} else {
+		u32 pkgid = topo_apicid(apic_id, TOPO_PKG_DOMAIN);
 
-	c->topo.core_id = apic->phys_pkg_id(c->topo.initial_apicid,
-				ht_mask_width) & core_select_mask;
+		/*
+		 * Check for present APICs in the same package when running
+		 * on bare metal. Allow the bogosity in a guest.
+		 */
+		if (hypervisor_is_type(X86_HYPER_NATIVE) &&
+		    topo_unit_count(pkgid, TOPO_PKG_DOMAIN, phys_cpu_present_map)) {
+			pr_info_once("Ignoring hot-pluggable APIC ID %x in present package.\n",
+				     apic_id);
+			topo_info.nr_rejected_cpus++;
+			return;
+		}
 
-	if (die_level_present) {
-		c->topo.die_id = apic->phys_pkg_id(c->topo.initial_apicid,
-					core_plus_mask_width) & die_select_mask;
+		topo_info.nr_disabled_cpus++;
 	}
 
-	c->topo.pkg_id = apic->phys_pkg_id(c->topo.initial_apicid, pkg_mask_width);
 	/*
-	 * Reinit the apicid, now that we have extended initial_apicid.
+	 * Register present and possible CPUs in the domain
+	 * maps. cpu_possible_map will be updated in
+	 * topology_init_possible_cpus() after enumeration is done.
 	 */
-	c->topo.apicid = apic->phys_pkg_id(c->topo.initial_apicid, 0);
+	for (dom = TOPO_SMT_DOMAIN; dom < TOPO_MAX_DOMAIN; dom++)
+		set_bit(topo_apicid(apic_id, dom), apic_maps[dom].map);
+}
+
+/**
+ * topology_register_apic - Register an APIC in early topology maps
+ * @apic_id:	The APIC ID to set up
+ * @acpi_id:	The ACPI ID associated to the APIC
+ * @present:	True if the corresponding CPU is present
+ */
+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 (check_for_real_bsp(apic_id)) {
+		topo_info.nr_rejected_cpus++;
+		return;
+	}
+
+	/* 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;
+	}
+
+	topo_register_apic(apic_id, acpi_id, present);
+}
+
+/**
+ * topology_register_boot_apic - Register the boot CPU APIC
+ * @apic_id:	The APIC ID to set up
+ *
+ * Separate so CPU #0 can be assigned
+ */
+void __init topology_register_boot_apic(u32 apic_id)
+{
+	WARN_ON_ONCE(topo_info.boot_cpu_apic_id != BAD_APICID);
+
+	topo_info.boot_cpu_apic_id = apic_id;
+	topo_register_apic(apic_id, CPU_ACPIID_INVALID, true);
+}
 
-	c->x86_max_cores = (core_level_siblings / smp_num_siblings);
-	__max_die_per_package = (die_level_siblings / core_level_siblings);
+/**
+ * topology_get_logical_id - Retrieve the logical ID at a given topology domain level
+ * @apicid:		The APIC ID for which to lookup the logical ID
+ * @at_level:		The topology domain level to use
+ *
+ * @apicid must be a full APIC ID, not the normalized variant. It's valid to have
+ * all bits below the domain level specified by @at_level to be clear. So both
+ * real APIC IDs and backshifted normalized APIC IDs work correctly.
+ *
+ * Returns:
+ *  - >= 0:	The requested logical ID
+ *  - -ERANGE:	@apicid is out of range
+ *  - -ENODEV:	@apicid is not registered
+ */
+int topology_get_logical_id(u32 apicid, enum x86_topology_domains at_level)
+{
+	/* Remove the bits below @at_level to get the proper level ID of @apicid */
+	unsigned int lvlid = topo_apicid(apicid, at_level);
+
+	if (lvlid >= MAX_LOCAL_APIC)
+		return -ERANGE;
+	if (!test_bit(lvlid, apic_maps[at_level].map))
+		return -ENODEV;
+	/* Get the number of set bits before @lvlid. */
+	return bitmap_weight(apic_maps[at_level].map, lvlid);
+}
+EXPORT_SYMBOL_GPL(topology_get_logical_id);
+
+/**
+ * topology_unit_count - Retrieve the count of specified units at a given topology domain level
+ * @apicid:		The APIC ID which specifies the search range
+ * @which_units:	The domain level specifying the units to count
+ * @at_level:		The domain level at which @which_units have to be counted
+ *
+ * This returns the number of possible units according to the enumerated
+ * information.
+ *
+ * E.g. topology_count_units(apicid, TOPO_CORE_DOMAIN, TOPO_PKG_DOMAIN)
+ * counts the number of possible cores in the package to which @apicid
+ * belongs.
+ *
+ * @at_level must obviously be greater than @which_level to produce useful
+ * results.  If @at_level is equal to @which_units the result is
+ * unsurprisingly 1. If @at_level is less than @which_units the results
+ * is by definition undefined and the function returns 0.
+ */
+unsigned int topology_unit_count(u32 apicid, enum x86_topology_domains which_units,
+				 enum x86_topology_domains at_level)
+{
+	/* Remove the bits below @at_level to get the proper level ID of @apicid */
+	unsigned int lvlid = topo_apicid(apicid, at_level);
+
+	if (lvlid >= MAX_LOCAL_APIC)
+		return 0;
+	if (!test_bit(lvlid, apic_maps[at_level].map))
+		return 0;
+	if (which_units > at_level)
+		return 0;
+	if (which_units == at_level)
+		return 1;
+	return topo_unit_count(lvlid, at_level, apic_maps[which_units].map);
+}
+
+#ifdef CONFIG_ACPI_HOTPLUG_CPU
+/**
+ * topology_hotplug_apic - Handle a physical hotplugged APIC after boot
+ * @apic_id:	The APIC ID to set up
+ * @acpi_id:	The ACPI ID associated to the APIC
+ */
+int topology_hotplug_apic(u32 apic_id, u32 acpi_id)
+{
+	int cpu;
+
+	if (apic_id >= MAX_LOCAL_APIC)
+		return -EINVAL;
+
+	/* Reject if the APIC ID was not registered during enumeration. */
+	if (!test_bit(apic_id, apic_maps[TOPO_SMT_DOMAIN].map))
+		return -ENODEV;
+
+	cpu = topo_lookup_cpuid(apic_id);
+	if (cpu < 0)
+		return -ENOSPC;
+
+	set_bit(apic_id, phys_cpu_present_map);
+	topo_set_cpuids(cpu, apic_id, acpi_id);
+	cpu_mark_primary_thread(cpu, apic_id);
+	return cpu;
+}
+
+/**
+ * topology_hotunplug_apic - Remove a physical hotplugged APIC after boot
+ * @cpu:	The CPU number for which the APIC ID is removed
+ */
+void topology_hotunplug_apic(unsigned int cpu)
+{
+	u32 apic_id = cpuid_to_apicid[cpu];
+
+	if (apic_id == BAD_APICID)
+		return;
+
+	per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
+	clear_bit(apic_id, phys_cpu_present_map);
+	set_cpu_present(cpu, false);
+}
 #endif
+
+#ifdef CONFIG_X86_LOCAL_APIC
+static unsigned int max_possible_cpus __initdata = NR_CPUS;
+
+/**
+ * topology_apply_cmdline_limits_early - Apply topology command line limits early
+ *
+ * Ensure that command line limits are in effect before firmware parsing
+ * takes place.
+ */
+void __init topology_apply_cmdline_limits_early(void)
+{
+	unsigned int possible = nr_cpu_ids;
+
+	/* 'maxcpus=0' 'nosmp' 'nolapic' 'disableapic' 'noapic' */
+	if (!setup_max_cpus || ioapic_is_disabled || apic_is_disabled)
+		possible = 1;
+
+	/* 'possible_cpus=N' */
+	possible = min_t(unsigned int, max_possible_cpus, possible);
+
+	if (possible < nr_cpu_ids) {
+		pr_info("Limiting to %u possible CPUs\n", possible);
+		set_nr_cpu_ids(possible);
+	}
+}
+
+static __init bool restrict_to_up(void)
+{
+	if (!smp_found_config || ioapic_is_disabled)
+		return true;
+	/*
+	 * XEN PV is special as it does not advertise the local APIC
+	 * properly, but provides a fake topology for it so that the
+	 * infrastructure works. So don't apply the restrictions vs. APIC
+	 * here.
+	 */
+	if (xen_pv_domain())
+		return false;
+
+	return apic_is_disabled;
+}
+
+void __init topology_init_possible_cpus(void)
+{
+	unsigned int assigned = topo_info.nr_assigned_cpus;
+	unsigned int disabled = topo_info.nr_disabled_cpus;
+	unsigned int cnta, cntb, cpu, allowed = 1;
+	unsigned int total = assigned + disabled;
+	u32 apicid, firstid;
+
+	/*
+	 * If there was no APIC registered, then fake one so that the
+	 * topology bitmap is populated. That ensures that the code below
+	 * is valid and the various query interfaces can be used
+	 * unconditionally. This does not affect the actual APIC code in
+	 * any way because either the local APIC address has not been
+	 * registered or the local APIC was disabled on the command line.
+	 */
+	if (topo_info.boot_cpu_apic_id == BAD_APICID)
+		topology_register_boot_apic(0);
+
+	if (!restrict_to_up()) {
+		if (WARN_ON_ONCE(assigned > nr_cpu_ids)) {
+			disabled += assigned - nr_cpu_ids;
+			assigned = nr_cpu_ids;
+		}
+		allowed = min_t(unsigned int, total, nr_cpu_ids);
+	}
+
+	if (total > allowed)
+		pr_warn("%u possible CPUs exceed the limit of %u\n", total, allowed);
+
+	assigned = min_t(unsigned int, allowed, assigned);
+	disabled = allowed - assigned;
+
+	topo_info.nr_assigned_cpus = assigned;
+	topo_info.nr_disabled_cpus = disabled;
+
+	total_cpus = allowed;
+	set_nr_cpu_ids(allowed);
+
+	cnta = domain_weight(TOPO_PKG_DOMAIN);
+	cntb = domain_weight(TOPO_DIE_DOMAIN);
+	__max_logical_packages = cnta;
+	__max_dies_per_package = 1U << (get_count_order(cntb) - get_count_order(cnta));
+
+	pr_info("Max. logical packages: %3u\n", cnta);
+	pr_info("Max. logical dies:     %3u\n", cntb);
+	pr_info("Max. dies per package: %3u\n", __max_dies_per_package);
+
+	cnta = domain_weight(TOPO_CORE_DOMAIN);
+	cntb = domain_weight(TOPO_SMT_DOMAIN);
+	/*
+	 * Can't use order delta here as order(cnta) can be equal
+	 * order(cntb) even if cnta != cntb.
+	 */
+	__max_threads_per_core = DIV_ROUND_UP(cntb, cnta);
+	pr_info("Max. threads per core: %3u\n", __max_threads_per_core);
+
+	firstid = find_first_bit(apic_maps[TOPO_SMT_DOMAIN].map, MAX_LOCAL_APIC);
+	__num_cores_per_package = topology_unit_count(firstid, TOPO_CORE_DOMAIN, TOPO_PKG_DOMAIN);
+	pr_info("Num. cores per package:   %3u\n", __num_cores_per_package);
+	__num_threads_per_package = topology_unit_count(firstid, TOPO_SMT_DOMAIN, TOPO_PKG_DOMAIN);
+	pr_info("Num. threads per package: %3u\n", __num_threads_per_package);
+
+	pr_info("Allowing %u present CPUs plus %u hotplug CPUs\n", assigned, disabled);
+	if (topo_info.nr_rejected_cpus)
+		pr_info("Rejected CPUs %u\n", topo_info.nr_rejected_cpus);
+
+	init_cpu_present(cpumask_of(0));
+	init_cpu_possible(cpumask_of(0));
+
+	/* Assign CPU numbers to non-present CPUs */
+	for (apicid = 0; disabled; disabled--, apicid++) {
+		apicid = find_next_andnot_bit(apic_maps[TOPO_SMT_DOMAIN].map, phys_cpu_present_map,
+					      MAX_LOCAL_APIC, apicid);
+		if (apicid >= MAX_LOCAL_APIC)
+			break;
+		cpuid_to_apicid[topo_info.nr_assigned_cpus++] = apicid;
+	}
+
+	for (cpu = 0; cpu < allowed; cpu++) {
+		apicid = cpuid_to_apicid[cpu];
+
+		set_cpu_possible(cpu, true);
+
+		if (apicid == BAD_APICID)
+			continue;
+
+		cpu_mark_primary_thread(cpu, apicid);
+		set_cpu_present(cpu, test_bit(apicid, phys_cpu_present_map));
+	}
+}
+
+/*
+ * Late SMP disable after sizing CPU masks when APIC/IOAPIC setup failed.
+ */
+void __init topology_reset_possible_cpus_up(void)
+{
+	init_cpu_present(cpumask_of(0));
+	init_cpu_possible(cpumask_of(0));
+
+	bitmap_zero(phys_cpu_present_map, MAX_LOCAL_APIC);
+	if (topo_info.boot_cpu_apic_id != BAD_APICID)
+		set_bit(topo_info.boot_cpu_apic_id, phys_cpu_present_map);
+}
+
+static int __init setup_possible_cpus(char *str)
+{
+	get_option(&str, &max_possible_cpus);
 	return 0;
 }
+early_param("possible_cpus", setup_possible_cpus);
+#endif