From: Zheng Zengkai zhengzengkai@huawei.com
hulk inclusion category: feature bugzilla: 51775 CVE: NA
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New config switch CONFIG_ARM64_BOOTPARAM_HOTPLUG_CPU0 sets default state of whether the CPU0 hotplug is on or off.
If the config switch is off, CPU0 is not hotpluggable by default. But the CPU0 hotplug feature can still be turned on by kernel parameter arm64_cpu0_hotplug at boot.
If the config switch is on, CPU0 is always hotpluggable.
The default value of the config switch is off.
Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Reviewed-by: Hanjun Guo guohanjun@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- .../admin-guide/kernel-parameters.txt | 8 ++++++ arch/arm64/Kconfig | 28 +++++++++++++++++++ arch/arm64/kernel/setup.c | 18 +++++++++++- 3 files changed, 53 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 1b733bcbdd763..564b14b0b9b84 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3176,6 +3176,14 @@ If the dependencies are under your control, you can turn on cpu0_hotplug.
+ arm64_cpu0_hotplug [ARM64] Turn on CPU0 hotplug feature 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 diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index bb9834277eeeb..2f3197d7385ba 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -810,6 +810,34 @@ 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 enable CPU0 hotplug by default. If this switch + is turned on, there is no need to give arm64_cpu0_hotplug kernel + parameter and the CPU0 hotplug feature is enabled 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 enable the CPU0 hotplug feature at boot by kernel + parameter arm64_cpu0_hotplug. + config ARM64_ERR_RECOV bool "Support arm64 RAS error recovery" depends on ACPI_APEI_SEA && MEMORY_FAILURE diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index 81156801afe13..64f12477016a1 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -68,6 +68,19 @@ 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;
/* @@ -401,7 +414,10 @@ static int __init topology_init(void)
for_each_present_cpu(i) { struct cpu *cpu = &per_cpu(cpu_data.cpu, i); - cpu->hotpluggable = 1; + if (i == 0) + cpu->hotpluggable = arm64_cpu0_hotpluggable; + else + cpu->hotpluggable = 1; register_cpu(cpu, i); }