Commit 2f465989 authored by Zheng Zengkai's avatar Zheng Zengkai
Browse files

arm64: Add config switch and kernel parameter for CPU0 hotplug 

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8RJPO


CVE: NA

-------------------------------------------------

New config switch CONFIG_ARM64_BOOTPARAM_HOTPLUG_CPU0 sets whether
default state of arm64_cpu0_hotpluggable is on or off.

If the config switch is off, arm64_cpu0_hotpluggable is off
by default. But arm64_cpu0_hotpluggable can still be turned on
by kernel parameter arm64_cpu0_hotplug at boot.

If the config switch is on, arm64_cpu0_hotpluggable is always on.

whether CPU0 is hotpluggable depends on cpu_can_disable(0) and
arm64_cpu0_hotpluggable.

The default value of the config switch is off.

Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 4eb5a1ca

Documentation/admin-guide/kernel-parameters.txt

+8 −0
Original line number Diff line number Diff line
@@ -3973,6 +3973,14 @@ 
			parameter, xsave area per process might occupy more

			memory on xsaves enabled systems.



	arm64_cpu0_hotplug [ARM64] Turn on arm64_cpu0_hotpluggable when

			CONFIG_ARM64_BOOTPARAM_HOTPLUG_CPU0 is off.

			Some features depend on CPU0. Known dependency is:

			MegaRAID Tri-Mode SAS3508 may block the reboot process

			after offline CPU0.

			If the dependencies are under your control, you can

			turn on arm64_cpu0_hotplug.



	nps_mtm_hs_ctr=	[KNL,ARC]

			This parameter sets the maximum duration, in

			cycles, each HW thread of the CTOP can run

arch/arm64/Kconfig

+28 −0
Original line number Diff line number Diff line
@@ -1456,6 +1456,34 @@ config HOTPLUG_CPU 
	  Say Y here to experiment with turning CPUs off and on.  CPUs

	  can be controlled through /sys/devices/system/cpu.



config ARM64_BOOTPARAM_HOTPLUG_CPU0

	bool "Set default setting of arm64_cpu0_hotpluggable"

	default n

	depends on HOTPLUG_CPU

	help

	  Set whether default state of arm64_cpu0_hotpluggable is on or off.



	  Say Y here to set arm64_cpu0_hotpluggable on by default. If this

	  switch is turned on, there is no need to give arm64_cpu0_hotplug

	  kernel parameter and arm64_cpu0_hotpluggable is on by default.



	  Please note: there may be some CPU0 dependencies if you want

	  to enable the CPU0 hotplug feature either by this switch or by

	  arm64_cpu0_hotplug kernel parameter.



	  For example:

	  We found the following issue related to CPU0 dependency:

	  1. echo 0 > /sys/devices/system/cpu/cpu0/online

	  2. reboot

	  MegaRAID Tri-Mode SAS3508 may block the reboot process.



	  Please make sure the dependencies are under your control before

	  you enable this feature.



	  Say N if you don't want to enable CPU0 hotplug feature by default.

	  You still can set arm64_cpu0_hotpluggable on at boot by kernel

	  parameter arm64_cpu0_hotplug.



# Common NUMA Features

config NUMA

	bool "NUMA Memory Allocation and Scheduler Support"

arch/arm64/kernel/setup.c

+19 −2
Original line number Diff line number Diff line
@@ -57,6 +57,19 @@ 
static int num_standard_resources;

static struct resource *standard_resources;



#ifdef CONFIG_ARM64_BOOTPARAM_HOTPLUG_CPU0

static int arm64_cpu0_hotpluggable = 1;

#else

static int arm64_cpu0_hotpluggable;

static int __init arm64_enable_cpu0_hotplug(char *str)

{

	arm64_cpu0_hotpluggable = 1;

	return 1;

}



__setup("arm64_cpu0_hotplug", arm64_enable_cpu0_hotplug);

#endif



phys_addr_t __fdt_pointer __initdata;

u64 mmu_enabled_at_boot __initdata;
@@ -396,8 +409,12 @@ static inline bool cpu_can_disable(unsigned int cpu) 
#ifdef CONFIG_HOTPLUG_CPU

	const struct cpu_operations *ops = get_cpu_ops(cpu);



	if (ops && ops->cpu_can_disable)

	if (ops && ops->cpu_can_disable) {

		if (cpu == 0)

			return ops->cpu_can_disable(0) && arm64_cpu0_hotpluggable;

		else

			return ops->cpu_can_disable(cpu);

	}

#endif

	return false;

}