CPU physical hot-add/hot-remove are supported on some hardwares, and it
was already supported in current linux kernel. NUMA Hotplug Emulator provides
a mechanism to emulate the process with software method. It can be used for
testing or debuging purpose.
CPU physical hotplug is different with logical CPU online/offline. Logical
online/offline is controled by interface /sys/device/cpu/cpuX/online. CPU
hotplug emulator uses probe/release interface. It becomes possible to do cpu
hotplug automation and stress
Add cpu interface probe/release under sysfs for x86_64. User can use this
interface to emulate the cpu hot-add and hot-remove process.
Directive:
*) Reserve CPU thru 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.
CC: Ingo Molnar <[email protected]>
CC: Len Brown <[email protected]>
CC: Yinghai Lu <[email protected]>
Signed-off-by: Shaohui Zheng <[email protected]>
Signed-off-by: Haicheng Li <[email protected]>
Signed-off-by: Yang Zhang <[email protected]>
---
Documentation/x86/x86_64/boot-options.txt | 5 ++
arch/x86/kernel/acpi/boot.c | 31 +++++++++++
arch/x86/kernel/smpboot.c | 2 -
arch/x86/kernel/topology.c | 81 ++++++++++++++++++++++++++++-
arch/x86/mm/numa_64.c | 15 +++++
drivers/acpi/processor_driver.c | 9 +++
drivers/base/cpu.c | 8 +++-
include/linux/acpi.h | 1 +
include/linux/cpu.h | 4 ++
9 files changed, 151 insertions(+), 5 deletions(-)
diff --git a/Documentation/x86/x86_64/boot-options.txt linux-hpe4/Documentation/x86/x86_64/boot-options.txt
index d8d5bf9..82fb04d 100644
--- a/Documentation/x86/x86_64/boot-options.txt
+++ linux-hpe4/Documentation/x86/x86_64/boot-options.txt
@@ -311,3 +311,8 @@ Miscellaneous
Do not use GB pages for kernel direct mappings.
gbpages
Use GB pages for kernel direct mappings.
+ cpu_hpe=on/off
+ Enable/disable CPU hotplug emulation with software method. When cpu_hpe=on,
+ sysfs provides probe/release interface to hot add/remove CPUs dynamically.
+ We can use maxcpus=<N> to reserve CPUs.
+ This option is disabled by default.
diff --git a/arch/x86/kernel/acpi/boot.c linux-hpe4/arch/x86/kernel/acpi/boot.c
index 9a966c5..cd3a896 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ linux-hpe4/arch/x86/kernel/acpi/boot.c
@@ -680,8 +680,39 @@ 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
+ set_apicid_to_node(physid, nid);
+ numa_set_node(cpu, nid);
+#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/smpboot.c linux-hpe4/arch/x86/kernel/smpboot.c
index c2871d3..f98122e 100644
--- a/arch/x86/kernel/smpboot.c
+++ linux-hpe4/arch/x86/kernel/smpboot.c
@@ -104,8 +104,6 @@ void cpu_hotplug_driver_unlock(void)
mutex_unlock(&x86_cpu_hotplug_driver_mutex);
}
-ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; }
-ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; }
#else
static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
#define get_idle_for_cpu(x) (idle_thread_array[(x)])
diff --git a/arch/x86/kernel/topology.c linux-hpe4/arch/x86/kernel/topology.c
index 1e53227..ab62c94 100644
--- a/arch/x86/kernel/topology.c
+++ linux-hpe4/arch/x86/kernel/topology.c
@@ -30,6 +30,9 @@
#include <linux/init.h>
#include <linux/smp.h>
#include <asm/cpu.h>
+#include <linux/cpu.h>
+#include <linux/topology.h>
+#include <linux/acpi.h>
static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
@@ -66,6 +69,74 @@ 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_node(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);
+
#else /* CONFIG_HOTPLUG_CPU */
static int __init arch_register_cpu(int num)
@@ -83,8 +154,14 @@ 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 linux-hpe4/arch/x86/mm/numa_64.c
index c3f8050..d13b5b8 100644
--- a/arch/x86/mm/numa_64.c
+++ linux-hpe4/arch/x86/mm/numa_64.c
@@ -14,6 +14,7 @@
#include <linux/nodemask.h>
#include <linux/sched.h>
#include <linux/acpi.h>
+#include <linux/cpu.h>
#include <asm/e820.h>
#include <asm/proto.h>
@@ -665,3 +666,17 @@ int __cpuinit numa_cpu_node(int cpu)
return __apicid_to_node[apicid];
return NUMA_NO_NODE;
}
+
+#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 */
diff --git a/drivers/acpi/processor_driver.c linux-hpe4/drivers/acpi/processor_driver.c
index 360a74e..e6da38a 100644
--- a/drivers/acpi/processor_driver.c
+++ linux-hpe4/drivers/acpi/processor_driver.c
@@ -492,6 +492,14 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
per_cpu(processors, pr->id) = pr;
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_free_cpumask;
@@ -532,6 +540,7 @@ 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 linux-hpe4/drivers/base/cpu.c
index 6b791ae..87be7a9 100644
--- a/drivers/base/cpu.c
+++ linux-hpe4/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)
{
diff --git a/include/linux/acpi.h linux-hpe4/include/linux/acpi.h
index a2e910e..9cd5676 100644
--- a/include/linux/acpi.h
+++ linux-hpe4/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 linux-hpe4/include/linux/cpu.h
index 014856d..a4258ba 100644
--- a/include/linux/cpu.h
+++ linux-hpe4/include/linux/cpu.h
@@ -25,6 +25,8 @@ struct cpu {
struct sys_device sysdev;
};
+DECLARE_PER_CPU(struct sys_device *, cpu_sys_devices);
+
extern int register_cpu_node(struct cpu *cpu, int num, int nid);
static inline int register_cpu(struct cpu *cpu, int num)
@@ -144,6 +146,7 @@ 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);
@@ -166,6 +169,7 @@ 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
--
1.7.1.1
---
best regards
yang