x86/cpu/topology: Move registration out of APIC code

The APIC/CPU registration sits in the middle of the APIC code. In fact this
is a topology evaluation function and has nothing to do with the inner
workings of the local APIC.

Move it out into a file which reflects what this is about.

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/20240213210251.543948812@linutronix.de

2 files changed, 191 insertions, 5 deletions

diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 9e0a1c119a91..eb4dbcdf41f1 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -26,14 +26,16 @@ obj-y			+= bugs.o
 obj-y			+= aperfmperf.o
 obj-y			+= cpuid-deps.o
 obj-y			+= umwait.o
+obj-y 			+= capflags.o powerflags.o
 
-obj-$(CONFIG_PROC_FS)	+= proc.o
-obj-y += capflags.o powerflags.o
+obj-$(CONFIG_X86_LOCAL_APIC)		+= topology.o
 
-obj-$(CONFIG_IA32_FEAT_CTL) += feat_ctl.o
+obj-$(CONFIG_PROC_FS)			+= proc.o
+
+obj-$(CONFIG_IA32_FEAT_CTL)		+= feat_ctl.o
 ifdef CONFIG_CPU_SUP_INTEL
-obj-y			+= intel.o intel_pconfig.o tsx.o
-obj-$(CONFIG_PM)	+= intel_epb.o
+obj-y					+= intel.o intel_pconfig.o tsx.o
+obj-$(CONFIG_PM)			+= intel_epb.o
 endif
 obj-$(CONFIG_CPU_SUP_AMD)		+= amd.o
 obj-$(CONFIG_CPU_SUP_HYGON)		+= hygon.o
diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
new file mode 100644
index 000000000000..b99cd19b7d12
--- /dev/null
+++ b/arch/x86/kernel/cpu/topology.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/cpu.h>
+
+#include <xen/xen.h>
+
+#include <asm/apic.h>
+#include <asm/mpspec.h>
+#include <asm/smp.h>
+
+/*
+ * 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);
+
+/* Bitmap of physically present CPUs. */
+DECLARE_BITMAP(phys_cpu_present_map, MAX_LOCAL_APIC) __read_mostly;
+
+/* Used for CPU number allocation and parallel CPU bringup */
+u32 cpuid_to_apicid[] __read_mostly = { [0 ... NR_CPUS - 1] = BAD_APICID, };
+
+/*
+ * Processor to be disabled specified by kernel parameter
+ * disable_cpu_apicid=<int>, mostly used for the kdump 2nd kernel to
+ * avoid undefined behaviour caused by sending INIT from AP to BSP.
+ */
+static u32 disabled_cpu_apicid __ro_after_init = BAD_APICID;
+
+unsigned int num_processors;
+unsigned disabled_cpus;
+
+/*
+ * The number of allocated logical CPU IDs. Since logical CPU IDs are allocated
+ * contiguously, it equals to current allocated max logical CPU ID plus 1.
+ * All allocated CPU IDs should be in the [0, nr_logical_cpuids) range,
+ * so the maximum of nr_logical_cpuids is nr_cpu_ids.
+ *
+ * NOTE: Reserve 0 for BSP.
+ */
+static int nr_logical_cpuids = 1;
+
+bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
+{
+	return phys_id == (u64)cpuid_to_apicid[cpu];
+}
+
+#ifdef CONFIG_SMP
+static void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid)
+{
+	/* Isolate the SMT bit(s) in the APICID and check for 0 */
+	u32 mask = (1U << (fls(smp_num_siblings) - 1)) - 1;
+
+	if (smp_num_siblings == 1 || !(apicid & mask))
+		cpumask_set_cpu(cpu, &__cpu_primary_thread_mask);
+}
+
+/*
+ * Due to the utter mess of CPUID evaluation smp_num_siblings is not valid
+ * during early boot. Initialize the primary thread mask before SMP
+ * bringup.
+ */
+static int __init smp_init_primary_thread_mask(void)
+{
+	unsigned int cpu;
+
+	/*
+	 * XEN/PV provides either none or useless topology information.
+	 * Pretend that all vCPUs are primary threads.
+	 */
+	if (xen_pv_domain()) {
+		cpumask_copy(&__cpu_primary_thread_mask, cpu_possible_mask);
+		return 0;
+	}
+
+	for (cpu = 0; cpu < nr_logical_cpuids; cpu++)
+		cpu_mark_primary_thread(cpu, cpuid_to_apicid[cpu]);
+	return 0;
+}
+early_initcall(smp_init_primary_thread_mask);
+#else
+static inline void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid) { }
+#endif
+
+/*
+ * Should use this API to allocate logical CPU IDs to keep nr_logical_cpuids
+ * and cpuid_to_apicid[] synchronized.
+ */
+static int allocate_logical_cpuid(int apicid)
+{
+	int i;
+
+	/*
+	 * cpuid <-> apicid mapping is persistent, so when a cpu is up,
+	 * check if the kernel has allocated a cpuid for it.
+	 */
+	for (i = 0; i < nr_logical_cpuids; i++) {
+		if (cpuid_to_apicid[i] == apicid)
+			return i;
+	}
+
+	/* Allocate a new cpuid. */
+	if (nr_logical_cpuids >= nr_cpu_ids) {
+		WARN_ONCE(1, "APIC: NR_CPUS/possible_cpus limit of %u reached. "
+			     "Processor %d/0x%x and the rest are ignored.\n",
+			     nr_cpu_ids, nr_logical_cpuids, apicid);
+		return -EINVAL;
+	}
+
+	cpuid_to_apicid[nr_logical_cpuids] = apicid;
+	return nr_logical_cpuids++;
+}
+
+static void cpu_update_apic(int cpu, u32 apicid)
+{
+#if defined(CONFIG_SMP) || defined(CONFIG_X86_64)
+	early_per_cpu(x86_cpu_to_apicid, cpu) = apicid;
+#endif
+	set_cpu_possible(cpu, true);
+	set_bit(apicid, phys_cpu_present_map);
+	set_cpu_present(cpu, true);
+	num_processors++;
+
+	if (system_state != SYSTEM_BOOTING)
+		cpu_mark_primary_thread(cpu, apicid);
+}
+
+void __init topology_register_boot_apic(u32 apic_id)
+{
+	cpuid_to_apicid[0] = apic_id;
+	cpu_update_apic(0, apic_id);
+}
+
+int generic_processor_info(int apicid)
+{
+	int cpu, max = nr_cpu_ids;
+
+	/* 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 = num_processors + disabled_cpus;
+
+		pr_warn("APIC: Disabling requested cpu. Processor %d/0x%x ignored.\n",
+			thiscpu, apicid);
+
+		disabled_cpus++;
+		return -ENODEV;
+	}
+
+	if (num_processors >= nr_cpu_ids) {
+		int thiscpu = max + disabled_cpus;
+
+		pr_warn("APIC: NR_CPUS/possible_cpus limit of %i reached. "
+			"Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
+
+		disabled_cpus++;
+		return -EINVAL;
+	}
+
+	cpu = allocate_logical_cpuid(apicid);
+	if (cpu < 0) {
+		disabled_cpus++;
+		return -EINVAL;
+	}
+
+	cpu_update_apic(cpu, apicid);
+	return cpu;
+}
+
+static int __init apic_set_disabled_cpu_apicid(char *arg)
+{
+	if (!arg || !get_option(&arg, &disabled_cpu_apicid))
+		return -EINVAL;
+
+	return 0;
+}
+early_param("disable_cpu_apicid", apic_set_disabled_cpu_apicid);