On 2013-12-12 18:36, Mark Rutland wrote:
On Thu, Dec 12, 2013 at 06:50:27AM +0000, Hanjun Guo wrote:
[...]
#endif diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index cb548f1..5c8e69c 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -18,3 +18,29 @@ void arch_fix_phys_package_id(int num, u32 slot) } EXPORT_SYMBOL_GPL(arch_fix_phys_package_id);
+#ifdef CONFIG_HOTPLUG_CPU +int __ref arch_register_cpu(int cpu) +{
struct cpuinfo_arm *cpuinfo = &per_cpu(cpu_data, cpu);/* BSP cann't be taken down on arm */if (cpu)cpuinfo->cpu.hotpluggable = 1;_why_ does the ACPI standard prohibit hotplugging the boot CPU?
ACPI spec has not limitations to hotplug the boot CPU, it depends on the arch.
In non-ACPI systems we can hotplug out the boot CPU (we can do so under KVM using PSCI).
If all the things (interrupts and etc) running on CPU0 can be migrated to other CPUs when offline a CPU, it can be hotplugable in ACPI way too.
I note that the x86 arch_register_cpu allows CPU0 to be hotpluggable on Intel systems as long as there are no dependencies on CPU0 being active. Surely we can test for something more fine-grained rather than disallowing CPU0 hotplug outright?
Ok, will update it when I formally send this patch out.
How does this interact with the existing arm64 hotplug code?
Some other patches are needed for ACPI based CPU hotplug,will send out when the ACPI core for ARM is ready, I will cc you and then you will know what's going on :)
Thanks Hanjun