[RFC,5/7] NUMA hotplug emulator

Shaohui Zheng
2010-05-13T12:19:18Z

[-- Attachment #1: Type: text/plain, Size: 12577 bytes --]

hotplug emulator: support cpu probe/release in x86

Add cpu interface probe/release under sysfs for x86. User can use this
interface to emulate the cpu hot-add process, it is for cpu hotplug
test purpose. Add a kernel option CONFIG_ARCH_CPU_PROBE_RELEASE for this
feature.

This interface provides a mechanism to emulate cpu hotplug with software
methods, it becomes possible to do cpu hotplug automation and stress
testing.

Directive:
*) Reserve CPU throu grub parameter like:
maxcpus=4

the rest CPUs will not be initiliazed.

*) Probe CPU
we can use the probe interface to hot-add new CPUs:
echo nid > /sys/devices/system/cpu/probe

*) Release a CPU
echo cpu > /sys/devices/system/cpu/release

A reserved CPU will be hot-added to the specified node.
1) nid == 0, the CPU will be added to the real node which the CPU
should be in
2) nid != 0, add the CPU to node nid even through it is a fake node.

Signed-off-by: Shaohui Zheng <shaohui.zheng@intel.com>
Signed-off-by: Haicheng Li <haicheng.li@intel.com>
---
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2c078c8..54ccb0d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1228,6 +1228,17 @@ config NODE_HOTPLUG_EMU
N is the number of hidden nodes, size is the memory size per
hidden node. This is only useful for debugging.

+config ARCH_CPU_PROBE_RELEASE
+ def_bool y
+ bool "CPU hotplug emulation"
+ depends on NUMA_HOTPLUG_EMU
+ ---help---
+ Enable cpu hotplug emulation. Reserve cpu with grub parameter
+ "maxcpus=N", where N is the initial CPU number, the rest physical
+ CPUs will not be initialized; there is a probe/release interface
+ is for cpu hot-add/hot-remove to specified node in software method.
+ This is for debuging and testing purpose
+
config NODES_SHIFT
int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
range 1 10
@@ -1651,6 +1662,9 @@ config HOTPLUG_CPU
( Note: power management support will enable this option
automatically on SMP systems. )
Say N if you want to disable CPU hotplug.
+config ARCH_CPU_PROBE_RELEASE
+ def_bool y
+ depends on HOTPLUG_CPU

config COMPAT_VDSO
def_bool y
diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index b185091..339ac2d 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -28,6 +28,9 @@ struct x86_cpu {
#ifdef CONFIG_HOTPLUG_CPU
extern int arch_register_cpu(int num);
extern void arch_unregister_cpu(int);
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+extern int arch_register_cpu_emu(int num, int nid);
+#endif
#endif

DECLARE_PER_CPU(int, cpu_state);
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index cd40aba..c3c7878 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -592,8 +592,44 @@ int __ref acpi_map_lsapic(acpi_handle handle, int *pcpu)
}
EXPORT_SYMBOL(acpi_map_lsapic);

+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+static void acpi_map_cpu2node_emu(int cpu, int physid, int nid)
+{
+#ifdef CONFIG_ACPI_NUMA
+#ifdef CONFIG_X86_64
+ apicid_to_node[physid] = nid;
+ numa_set_node(cpu, nid);
+#else /* CONFIG_X86_32 */
+ apicid_2_node[physid] = nid;
+ cpu_to_node_map[cpu] = nid;
+#endif
+#endif
+}
+
+static u16 cpu_to_apicid_saved[CONFIG_NR_CPUS];
+int __ref acpi_map_lsapic_emu(int pcpu, int nid)
+{
+ /* backup cpu apicid to array cpu_to_apicid_saved */
+ if (cpu_to_apicid_saved[pcpu] == 0 &&
+ per_cpu(x86_cpu_to_apicid, pcpu) != BAD_APICID)
+ cpu_to_apicid_saved[pcpu] = per_cpu(x86_cpu_to_apicid, pcpu);
+
+ per_cpu(x86_cpu_to_apicid, pcpu) = cpu_to_apicid_saved[pcpu];
+ acpi_map_cpu2node_emu(pcpu, per_cpu(x86_cpu_to_apicid, pcpu), nid);
+
+ return pcpu;
+}
+EXPORT_SYMBOL(acpi_map_lsapic_emu);
+#endif
+
int acpi_unmap_lsapic(int cpu)
{
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+ /* backup cpu apicid to array cpu_to_apicid_saved */
+ if (cpu_to_apicid_saved[cpu] == 0 &&
+ per_cpu(x86_cpu_to_apicid, cpu) != BAD_APICID)
+ cpu_to_apicid_saved[cpu] = per_cpu(x86_cpu_to_apicid, cpu);
+#endif
per_cpu(x86_cpu_to_apicid, cpu) = -1;
set_cpu_present(cpu, false);
num_processors--;
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index f716cd9..3a7b788 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -29,6 +29,9 @@
#include <linux/mmzone.h>
#include <linux/init.h>
#include <linux/smp.h>
+#include <linux/cpu.h>
+#include <linux/topology.h>
+#include <linux/acpi.h>
#include <asm/cpu.h>

static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
@@ -37,6 +40,11 @@ static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
/*
* Add nid(NUMA node id) as parameter for cpu hotplug emulation. It supports
* to register a CPU to any nodes.
+ *
+ * nid is a special parameter, it has 2 different branches:
+ * 1) when nid == NUMA_NO_NODE, the CPU will be registered into the normal node
+ * which it should be in.
+ * 2) nid != NUMA_NO_NODE, it will be registered into the specified node.
*/
static int __ref __arch_register_cpu(int num, int nid)
{
@@ -52,9 +60,24 @@ static int __ref __arch_register_cpu(int num, int nid)
if (num)
per_cpu(cpu_devices, num).cpu.hotpluggable = 1;

- return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
+ if (nid == NUMA_NO_NODE)
+ return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
+ else
+ return register_cpu_emu(&per_cpu(cpu_devices, num).cpu, num, nid);
}

+/*
+ * Emulated version of function arch_register_cpu
+ * Parameter:
+ * num: cpu_id
+ * nid: emulated numa id
+ */
+int __ref arch_register_cpu_emu(int num, int nid)
+{
+ return __arch_register_cpu(num, nid);
+}
+EXPORT_SYMBOL(arch_register_cpu_emu);
+
int __ref arch_register_cpu(int num)
{
return __arch_register_cpu(num, NUMA_NO_NODE);
@@ -66,6 +89,84 @@ void arch_unregister_cpu(int num)
unregister_cpu(&per_cpu(cpu_devices, num).cpu);
}
EXPORT_SYMBOL(arch_unregister_cpu);
+
+ssize_t arch_cpu_probe(const char *buf, size_t count)
+{
+ int nid = 0;
+ int num = 0, selected = 0;
+
+ /* check parameters */
+ if (!buf || count < 2)
+ return -EPERM;
+
+ nid = simple_strtoul(buf, NULL, 0);
+ printk(KERN_DEBUG "Add a cpu to node : %d\n", nid);
+
+ if (nid < 0 || nid > nr_node_ids - 1) {
+ printk(KERN_ERR "Invalid NUMA node id: %d (0 <= nid < %d).\n",
+ nid, nr_node_ids);
+ return -EPERM;
+ }
+
+ if (!node_online(nid)) {
+ printk(KERN_ERR "NUMA node %d is not online, give up.\n", nid);
+ return -EPERM;
+ }
+
+ /* find first uninitialized cpu */
+ for_each_present_cpu(num) {
+ if (per_cpu(cpu_sys_devices, num) == NULL) {
+ selected = num;
+ break;
+ }
+ }
+
+ if (selected >= num_possible_cpus()) {
+ printk(KERN_ERR "No free cpu, give up cpu probing.\n");
+ return -EPERM;
+ }
+
+ /* register cpu */
+ arch_register_cpu_emu(selected, nid);
+ acpi_map_lsapic_emu(selected, nid);
+
+ return count;
+}
+EXPORT_SYMBOL(arch_cpu_probe);
+
+ssize_t arch_cpu_release(const char *buf, size_t count)
+{
+ int cpu = 0;
+
+ cpu = simple_strtoul(buf, NULL, 0);
+ /* cpu 0 is not hotplugable */
+ if (cpu == 0) {
+ printk(KERN_ERR "can not release cpu 0.\n");
+ return -EPERM;
+ }
+
+ if (cpu_online(cpu)) {
+ printk(KERN_DEBUG "offline cpu %d.\n", cpu);
+ cpu_down(cpu);
+ }
+
+ arch_unregister_cpu(cpu);
+ acpi_unmap_lsapic(cpu);
+
+ return count;
+}
+EXPORT_SYMBOL(arch_cpu_release);
+
+void cpu_hotplug_driver_unlock(void)
+{
+}
+EXPORT_SYMBOL(cpu_hotplug_driver_unlock);
+
+void cpu_hotplug_driver_lock(void)
+{
+}
+EXPORT_SYMBOL(cpu_hotplug_driver_lock);
+
#else /* CONFIG_HOTPLUG_CPU */

static int __init arch_register_cpu(int num)
@@ -83,8 +184,14 @@ static int __init topology_init(void)
register_one_node(i);
#endif

- for_each_present_cpu(i)
- arch_register_cpu(i);
+ /*
+ * when cpu hotplug emulation enabled, register the online cpu only,
+ * the rests are reserved for cpu probe.
+ */
+ for_each_present_cpu(i) {
+ if ((cpu_hpe_on && cpu_online(i)) || !cpu_hpe_on)
+ arch_register_cpu(i);
+ }

return 0;
}
diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index 7c61208..3430ff2 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -12,6 +12,7 @@
#include <linux/module.h>
#include <linux/nodemask.h>
#include <linux/sched.h>
+#include <linux/cpu.h>

#include <asm/e820.h>
#include <asm/proto.h>
@@ -889,6 +890,19 @@ void __init init_cpu_to_node(void)
}
#endif

+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+static __init int cpu_hpe_setup(char *opt)
+{
+ if (!opt)
+ return -EINVAL;
+
+ if (!strncmp(opt, "on", 2) || !strncmp(opt, "1", 1))
+ cpu_hpe_on = 1;
+
+ return 0;
+}
+early_param("cpu_hpe", cpu_hpe_setup);
+#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */

void __cpuinit numa_set_node(int cpu, int node)
{
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 5675d97..e024143 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -604,6 +604,14 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
goto err_free_cpumask;

sysdev = get_cpu_sysdev(pr->id);
+ /*
+ * Reserve cpu for hotplug emulation, the reserved cpu can be hot-added
+ * throu the cpu probe interface. Return directly.
+ */
+ if (sysdev == NULL) {
+ goto out;
+ }
+
if (sysfs_create_link(&device->dev.kobj, &sysdev->kobj, "sysdev")) {
result = -EFAULT;
goto err_remove_fs;
@@ -643,6 +651,7 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
goto err_remove_sysfs;
}

+out:
return 0;

err_remove_sysfs:
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index a1bc9c6..3225b32 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -22,9 +22,15 @@ struct sysdev_class cpu_sysdev_class = {
};
EXPORT_SYMBOL(cpu_sysdev_class);

-static DEFINE_PER_CPU(struct sys_device *, cpu_sys_devices);
+DEFINE_PER_CPU(struct sys_device *, cpu_sys_devices);

#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * cpu_hpe_on is a switch to enable/disable cpu hotplug emulation. it is
+ * disabled in default, we can enable it throu grub parameter cpu_hpe=on
+ */
+int cpu_hpe_on;
+
static ssize_t show_online(struct sys_device *dev, struct sysdev_attribute *attr,
char *buf)
{
@@ -80,6 +86,7 @@ void unregister_cpu(struct cpu *cpu)
}

#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+
static ssize_t cpu_probe_store(struct sysdev_class *class,
struct sysdev_class_attribute *attr,
const char *buf,
@@ -250,6 +257,18 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
return __register_cpu(cpu, num, cpu_to_node(num));
}

+/*
+ * Register cpu to the specified NUMA node
+ *
+ * emulated version of function register_cpu, but is more flexible. it supports
+ * an extra parameter nid, We can register a CPU to any specified node throu
+ * this function.
+ */
+int __cpuinit register_cpu_emu(struct cpu *cpu, int num, int nid)
+{
+ return __register_cpu(cpu, num, nid);
+}
+
struct sys_device *get_cpu_sysdev(unsigned cpu)
{
if (cpu < nr_cpu_ids && cpu_possible(cpu))
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index b926afe..c3bc5c7 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -102,6 +102,7 @@ void acpi_numa_arch_fixup(void);
#ifdef CONFIG_ACPI_HOTPLUG_CPU
/* Arch dependent functions for cpu hotplug support */
int acpi_map_lsapic(acpi_handle handle, int *pcpu);
+int acpi_map_lsapic_emu(int pcpu, int nid);
int acpi_unmap_lsapic(int cpu);
#endif /* CONFIG_ACPI_HOTPLUG_CPU */

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index e287863..2d4df89 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -30,7 +30,10 @@ struct cpu {
struct sys_device sysdev;
};

+DECLARE_PER_CPU(struct sys_device *, cpu_sys_devices);
+
extern int register_cpu(struct cpu *cpu, int num);
+extern int register_cpu_emu(struct cpu *cpu, int num, int nid);
extern struct sys_device *get_cpu_sysdev(unsigned cpu);

extern int cpu_add_sysdev_attr(struct sysdev_attribute *attr);
@@ -116,6 +119,7 @@ extern void put_online_cpus(void);
#define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
#define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
int cpu_down(unsigned int cpu);
+extern int cpu_hpe_on;

#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
extern void cpu_hotplug_driver_lock(void);
@@ -138,6 +142,7 @@ static inline void cpu_hotplug_driver_unlock(void)
/* These aren't inline functions due to a GCC bug. */
#define register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
#define unregister_hotcpu_notifier(nb) ({ (void)(nb); })
+static int cpu_hpe_on;
#endif /* CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_PM_SLEEP_SMP
--
Thanks & Regards,
Shaohui

[-- Attachment #2: 005-hotplug-emulator-x86-support-cpu-probe-release-in-x86.patch --]
[-- Type: text/x-diff, Size: 12546 bytes --]

hotplug emulator: support cpu probe/release in x86

Add cpu interface probe/release under sysfs for x86. User can use this
interface to emulate the cpu hot-add process, it is for cpu hotplug
test purpose. Add a kernel option CONFIG_ARCH_CPU_PROBE_RELEASE for this
feature.

This interface provides a mechanism to emulate cpu hotplug with software
methods, it becomes possible to do cpu hotplug automation and stress
testing.

Directive:
*) Reserve CPU throu grub parameter like:
maxcpus=4

the rest CPUs will not be initiliazed.

*) Probe CPU
we can use the probe interface to hot-add new CPUs:
echo nid > /sys/devices/system/cpu/probe

*) Release a CPU
echo cpu > /sys/devices/system/cpu/release

A reserved CPU will be hot-added to the specified node.
1) nid == 0, the CPU will be added to the real node which the CPU
should be in
2) nid != 0, add the CPU to node nid even through it is a fake node.

Signed-off-by: Shaohui Zheng <shaohui.zheng@intel.com>
Signed-off-by: Haicheng Li <haicheng.li@intel.com>
---
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2c078c8..54ccb0d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1228,6 +1228,17 @@ config NODE_HOTPLUG_EMU
N is the number of hidden nodes, size is the memory size per
hidden node. This is only useful for debugging.

+config ARCH_CPU_PROBE_RELEASE
+ def_bool y
+ bool "CPU hotplug emulation"
+ depends on NUMA_HOTPLUG_EMU
+ ---help---
+ Enable cpu hotplug emulation. Reserve cpu with grub parameter
+ "maxcpus=N", where N is the initial CPU number, the rest physical
+ CPUs will not be initialized; there is a probe/release interface
+ is for cpu hot-add/hot-remove to specified node in software method.
+ This is for debuging and testing purpose
+
config NODES_SHIFT
int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
range 1 10
@@ -1651,6 +1662,9 @@ config HOTPLUG_CPU
( Note: power management support will enable this option
automatically on SMP systems. )
Say N if you want to disable CPU hotplug.
+config ARCH_CPU_PROBE_RELEASE
+ def_bool y
+ depends on HOTPLUG_CPU

config COMPAT_VDSO
def_bool y
diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index b185091..339ac2d 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -28,6 +28,9 @@ struct x86_cpu {
#ifdef CONFIG_HOTPLUG_CPU
extern int arch_register_cpu(int num);
extern void arch_unregister_cpu(int);
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+extern int arch_register_cpu_emu(int num, int nid);
+#endif
#endif

DECLARE_PER_CPU(int, cpu_state);
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index cd40aba..c3c7878 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -592,8 +592,44 @@ int __ref acpi_map_lsapic(acpi_handle handle, int *pcpu)
}
EXPORT_SYMBOL(acpi_map_lsapic);

+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+static void acpi_map_cpu2node_emu(int cpu, int physid, int nid)
+{
+#ifdef CONFIG_ACPI_NUMA
+#ifdef CONFIG_X86_64
+ apicid_to_node[physid] = nid;
+ numa_set_node(cpu, nid);
+#else /* CONFIG_X86_32 */
+ apicid_2_node[physid] = nid;
+ cpu_to_node_map[cpu] = nid;
+#endif
+#endif
+}
+
+static u16 cpu_to_apicid_saved[CONFIG_NR_CPUS];
+int __ref acpi_map_lsapic_emu(int pcpu, int nid)
+{
+ /* backup cpu apicid to array cpu_to_apicid_saved */
+ if (cpu_to_apicid_saved[pcpu] == 0 &&
+ per_cpu(x86_cpu_to_apicid, pcpu) != BAD_APICID)
+ cpu_to_apicid_saved[pcpu] = per_cpu(x86_cpu_to_apicid, pcpu);
+
+ per_cpu(x86_cpu_to_apicid, pcpu) = cpu_to_apicid_saved[pcpu];
+ acpi_map_cpu2node_emu(pcpu, per_cpu(x86_cpu_to_apicid, pcpu), nid);
+
+ return pcpu;
+}
+EXPORT_SYMBOL(acpi_map_lsapic_emu);
+#endif
+
int acpi_unmap_lsapic(int cpu)
{
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+ /* backup cpu apicid to array cpu_to_apicid_saved */
+ if (cpu_to_apicid_saved[cpu] == 0 &&
+ per_cpu(x86_cpu_to_apicid, cpu) != BAD_APICID)
+ cpu_to_apicid_saved[cpu] = per_cpu(x86_cpu_to_apicid, cpu);
+#endif
per_cpu(x86_cpu_to_apicid, cpu) = -1;
set_cpu_present(cpu, false);
num_processors--;
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index f716cd9..3a7b788 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -29,6 +29,9 @@
#include <linux/mmzone.h>
#include <linux/init.h>
#include <linux/smp.h>
+#include <linux/cpu.h>
+#include <linux/topology.h>
+#include <linux/acpi.h>
#include <asm/cpu.h>

static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
@@ -37,6 +40,11 @@ static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
/*
* Add nid(NUMA node id) as parameter for cpu hotplug emulation. It supports
* to register a CPU to any nodes.
+ *
+ * nid is a special parameter, it has 2 different branches:
+ * 1) when nid == NUMA_NO_NODE, the CPU will be registered into the normal node
+ * which it should be in.
+ * 2) nid != NUMA_NO_NODE, it will be registered into the specified node.
*/
static int __ref __arch_register_cpu(int num, int nid)
{
@@ -52,9 +60,24 @@ static int __ref __arch_register_cpu(int num, int nid)
if (num)
per_cpu(cpu_devices, num).cpu.hotpluggable = 1;

- return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
+ if (nid == NUMA_NO_NODE)
+ return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
+ else
+ return register_cpu_emu(&per_cpu(cpu_devices, num).cpu, num, nid);
}

+/*
+ * Emulated version of function arch_register_cpu
+ * Parameter:
+ * num: cpu_id
+ * nid: emulated numa id
+ */
+int __ref arch_register_cpu_emu(int num, int nid)
+{
+ return __arch_register_cpu(num, nid);
+}
+EXPORT_SYMBOL(arch_register_cpu_emu);
+
int __ref arch_register_cpu(int num)
{
return __arch_register_cpu(num, NUMA_NO_NODE);
@@ -66,6 +89,84 @@ void arch_unregister_cpu(int num)
unregister_cpu(&per_cpu(cpu_devices, num).cpu);
}
EXPORT_SYMBOL(arch_unregister_cpu);
+
+ssize_t arch_cpu_probe(const char *buf, size_t count)
+{
+ int nid = 0;
+ int num = 0, selected = 0;
+
+ /* check parameters */
+ if (!buf || count < 2)
+ return -EPERM;
+
+ nid = simple_strtoul(buf, NULL, 0);
+ printk(KERN_DEBUG "Add a cpu to node : %d\n", nid);
+
+ if (nid < 0 || nid > nr_node_ids - 1) {
+ printk(KERN_ERR "Invalid NUMA node id: %d (0 <= nid < %d).\n",
+ nid, nr_node_ids);
+ return -EPERM;
+ }
+
+ if (!node_online(nid)) {
+ printk(KERN_ERR "NUMA node %d is not online, give up.\n", nid);
+ return -EPERM;
+ }
+
+ /* find first uninitialized cpu */
+ for_each_present_cpu(num) {
+ if (per_cpu(cpu_sys_devices, num) == NULL) {
+ selected = num;
+ break;
+ }
+ }
+
+ if (selected >= num_possible_cpus()) {
+ printk(KERN_ERR "No free cpu, give up cpu probing.\n");
+ return -EPERM;
+ }
+
+ /* register cpu */
+ arch_register_cpu_emu(selected, nid);
+ acpi_map_lsapic_emu(selected, nid);
+
+ return count;
+}
+EXPORT_SYMBOL(arch_cpu_probe);
+
+ssize_t arch_cpu_release(const char *buf, size_t count)
+{
+ int cpu = 0;
+
+ cpu = simple_strtoul(buf, NULL, 0);
+ /* cpu 0 is not hotplugable */
+ if (cpu == 0) {
+ printk(KERN_ERR "can not release cpu 0.\n");
+ return -EPERM;
+ }
+
+ if (cpu_online(cpu)) {
+ printk(KERN_DEBUG "offline cpu %d.\n", cpu);
+ cpu_down(cpu);
+ }
+
+ arch_unregister_cpu(cpu);
+ acpi_unmap_lsapic(cpu);
+
+ return count;
+}
+EXPORT_SYMBOL(arch_cpu_release);
+
+void cpu_hotplug_driver_unlock(void)
+{
+}
+EXPORT_SYMBOL(cpu_hotplug_driver_unlock);
+
+void cpu_hotplug_driver_lock(void)
+{
+}
+EXPORT_SYMBOL(cpu_hotplug_driver_lock);
+
#else /* CONFIG_HOTPLUG_CPU */

static int __init arch_register_cpu(int num)
@@ -83,8 +184,14 @@ static int __init topology_init(void)
register_one_node(i);
#endif

- for_each_present_cpu(i)
- arch_register_cpu(i);
+ /*
+ * when cpu hotplug emulation enabled, register the online cpu only,
+ * the rests are reserved for cpu probe.
+ */
+ for_each_present_cpu(i) {
+ if ((cpu_hpe_on && cpu_online(i)) || !cpu_hpe_on)
+ arch_register_cpu(i);
+ }

return 0;
}
diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index 7c61208..3430ff2 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -12,6 +12,7 @@
#include <linux/module.h>
#include <linux/nodemask.h>
#include <linux/sched.h>
+#include <linux/cpu.h>

#include <asm/e820.h>
#include <asm/proto.h>
@@ -889,6 +890,19 @@ void __init init_cpu_to_node(void)
}
#endif

+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+static __init int cpu_hpe_setup(char *opt)
+{
+ if (!opt)
+ return -EINVAL;
+
+ if (!strncmp(opt, "on", 2) || !strncmp(opt, "1", 1))
+ cpu_hpe_on = 1;
+
+ return 0;
+}
+early_param("cpu_hpe", cpu_hpe_setup);
+#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */

void __cpuinit numa_set_node(int cpu, int node)
{
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 5675d97..e024143 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -604,6 +604,14 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
goto err_free_cpumask;

sysdev = get_cpu_sysdev(pr->id);
+ /*
+ * Reserve cpu for hotplug emulation, the reserved cpu can be hot-added
+ * throu the cpu probe interface. Return directly.
+ */
+ if (sysdev == NULL) {
+ goto out;
+ }
+
if (sysfs_create_link(&device->dev.kobj, &sysdev->kobj, "sysdev")) {
result = -EFAULT;
goto err_remove_fs;
@@ -643,6 +651,7 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
goto err_remove_sysfs;
}

+out:
return 0;

err_remove_sysfs:
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index a1bc9c6..3225b32 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -22,9 +22,15 @@ struct sysdev_class cpu_sysdev_class = {
};
EXPORT_SYMBOL(cpu_sysdev_class);

-static DEFINE_PER_CPU(struct sys_device *, cpu_sys_devices);
+DEFINE_PER_CPU(struct sys_device *, cpu_sys_devices);

#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * cpu_hpe_on is a switch to enable/disable cpu hotplug emulation. it is
+ * disabled in default, we can enable it throu grub parameter cpu_hpe=on
+ */
+int cpu_hpe_on;
+
static ssize_t show_online(struct sys_device *dev, struct sysdev_attribute *attr,
char *buf)
{
@@ -80,6 +86,7 @@ void unregister_cpu(struct cpu *cpu)
}

#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+
static ssize_t cpu_probe_store(struct sysdev_class *class,
struct sysdev_class_attribute *attr,
const char *buf,
@@ -250,6 +257,18 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
return __register_cpu(cpu, num, cpu_to_node(num));
}

+/*
+ * Register cpu to the specified NUMA node
+ *
+ * emulated version of function register_cpu, but is more flexible. it supports
+ * an extra parameter nid, We can register a CPU to any specified node throu
+ * this function.
+ */
+int __cpuinit register_cpu_emu(struct cpu *cpu, int num, int nid)
+{
+ return __register_cpu(cpu, num, nid);
+}
+
struct sys_device *get_cpu_sysdev(unsigned cpu)
{
if (cpu < nr_cpu_ids && cpu_possible(cpu))
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index b926afe..c3bc5c7 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -102,6 +102,7 @@ void acpi_numa_arch_fixup(void);
#ifdef CONFIG_ACPI_HOTPLUG_CPU
/* Arch dependent functions for cpu hotplug support */
int acpi_map_lsapic(acpi_handle handle, int *pcpu);
+int acpi_map_lsapic_emu(int pcpu, int nid);
int acpi_unmap_lsapic(int cpu);
#endif /* CONFIG_ACPI_HOTPLUG_CPU */

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index e287863..2d4df89 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -30,7 +30,10 @@ struct cpu {
struct sys_device sysdev;
};

+DECLARE_PER_CPU(struct sys_device *, cpu_sys_devices);
+
extern int register_cpu(struct cpu *cpu, int num);
+extern int register_cpu_emu(struct cpu *cpu, int num, int nid);
extern struct sys_device *get_cpu_sysdev(unsigned cpu);

extern int cpu_add_sysdev_attr(struct sysdev_attribute *attr);
@@ -116,6 +119,7 @@ extern void put_online_cpus(void);
#define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
#define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
int cpu_down(unsigned int cpu);
+extern int cpu_hpe_on;

#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
extern void cpu_hotplug_driver_lock(void);
@@ -138,6 +142,7 @@ static inline void cpu_hotplug_driver_unlock(void)
/* These aren't inline functions due to a GCC bug. */
#define register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
#define unregister_hotcpu_notifier(nb) ({ (void)(nb); })
+static int cpu_hpe_on;
#endif /* CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_PM_SLEEP_SMP