3 files changed, 59 insertions, 9 deletions

diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
index c2f94dcc92ce..32007041ef8c 100644
--- a/arch/x86/include/asm/mpspec.h
+++ b/arch/x86/include/asm/mpspec.h
@@ -86,6 +86,7 @@ static inline void early_reserve_e820_mpc_new(void) { }
 #endif
 
 int generic_processor_info(int apicid, int version);
+int __generic_processor_info(int apicid, int version, bool enabled);
 
 #define PHYSID_ARRAY_SIZE       BITS_TO_LONGS(MAX_LOCAL_APIC)
 
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 0447e314e7f5..7d668d172fce 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -176,15 +176,10 @@ static int acpi_register_lapic(int id, u32 acpiid, u8 enabled)
                 return -EINVAL;
         }
 
-        if (!enabled) {
-                ++disabled_cpus;
-                return -EINVAL;
-        }
-
         if (boot_cpu_physical_apicid != -1U)
                 ver = boot_cpu_apic_version;
 
-        cpu = generic_processor_info(id, ver);
+        cpu = __generic_processor_info(id, ver, enabled);
         if (cpu >= 0)
                 early_per_cpu(x86_cpu_to_acpiid, cpu) = acpiid;
 
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index a8c94bb6b528..2dc01c38ad8e 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2021,7 +2021,53 @@ void disconnect_bsp_APIC(int virt_wire_setup)
         apic_write(APIC_LVT1, value);
 }
 
-static int __generic_processor_info(int apicid, int version, bool enabled)
+/*
+ * 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 ID should be in [0, nr_logical_cpuidi), so the maximum of
+ * nr_logical_cpuids is nr_cpu_ids.
+ *
+ * NOTE: Reserve 0 for BSP.
+ */
+static int nr_logical_cpuids = 1;
+
+/*
+ * Used to store mapping between logical CPU IDs and APIC IDs.
+ */
+static int cpuid_to_apicid[] = {
+        [0 ... NR_CPUS - 1] = -1,
+};
+
+/*
+ * 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, "Only %d processors supported."
+                             "Processor %d/0x%x and the rest are ignored.\n",
+                             nr_cpu_ids - 1, nr_logical_cpuids, apicid);
+                return -1;
+        }
+
+        cpuid_to_apicid[nr_logical_cpuids] = apicid;
+        return nr_logical_cpuids++;
+}
+
+int __generic_processor_info(int apicid, int version, bool enabled)
 {
         int cpu, max = nr_cpu_ids;
         bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
@@ -2096,8 +2142,16 @@ static int __generic_processor_info(int apicid, int version, bool enabled)
                  * for BSP.
                  */
                 cpu = 0;
-        } else
-                cpu = cpumask_next_zero(-1, cpu_present_mask);
+
+                /* Logical cpuid 0 is reserved for BSP. */
+                cpuid_to_apicid[0] = apicid;
+        } else {
+                cpu = allocate_logical_cpuid(apicid);
+                if (cpu < 0) {
+                        disabled_cpus++;
+                        return -EINVAL;
+                }
+        }
 
         /*
          * This can happen on physical hotplug. The sanity check at boot time