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authorThomas Gleixner <tglx@linutronix.de>2023-05-13 00:07:04 +0300
committerPeter Zijlstra <peterz@infradead.org>2023-05-15 14:44:49 +0300
commite59e74dc48a309cb848ffc3d76a0d61aa6803c05 (patch)
tree9e58c48aff3090ed62f0d81d0f7443160ba82ed7 /Documentation
parent666e1156b2c514f045827f50263ed2eb9d78671b (diff)
downloadlinux-e59e74dc48a309cb848ffc3d76a0d61aa6803c05.tar.xz
x86/topology: Remove CPU0 hotplug option
This was introduced together with commit e1c467e69040 ("x86, hotplug: Wake up CPU0 via NMI instead of INIT, SIPI, SIPI") to eventually support physical hotplug of CPU0: "We'll change this code in the future to wake up hard offlined CPU0 if real platform and request are available." 11 years later this has not happened and physical hotplug is not officially supported. Remove the cruft. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Michael Kelley <mikelley@microsoft.com> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Tested-by: Helge Deller <deller@gmx.de> # parisc Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck Link: https://lore.kernel.org/r/20230512205255.715707999@linutronix.de
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt14
-rw-r--r--Documentation/core-api/cpu_hotplug.rst13
2 files changed, 2 insertions, 25 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9e5bab29685f..ccb91a255c6d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -818,20 +818,6 @@
Format:
<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
- cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
- CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
- Some features depend on CPU0. Known dependencies are:
- 1. Resume from suspend/hibernate depends on CPU0.
- Suspend/hibernate will fail if CPU0 is offline and you
- need to online CPU0 before suspend/hibernate.
- 2. PIC interrupts also depend on CPU0. CPU0 can't be
- removed if a PIC interrupt is detected.
- It's said poweroff/reboot may depend on CPU0 on some
- machines although I haven't seen such issues so far
- after CPU0 is offline on a few tested machines.
- If the dependencies are under your control, you can
- turn on cpu0_hotplug.
-
cpuidle.off=1 [CPU_IDLE]
disable the cpuidle sub-system
diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst
index f75778d37488..e6f5bc39cf5c 100644
--- a/Documentation/core-api/cpu_hotplug.rst
+++ b/Documentation/core-api/cpu_hotplug.rst
@@ -127,17 +127,8 @@ bring CPU4 back online::
$ echo 1 > /sys/devices/system/cpu/cpu4/online
smpboot: Booting Node 0 Processor 4 APIC 0x1
-The CPU is usable again. This should work on all CPUs. CPU0 is often special
-and excluded from CPU hotplug. On X86 the kernel option
-*CONFIG_BOOTPARAM_HOTPLUG_CPU0* has to be enabled in order to be able to
-shutdown CPU0. Alternatively the kernel command option *cpu0_hotplug* can be
-used. Some known dependencies of CPU0:
-
-* Resume from hibernate/suspend. Hibernate/suspend will fail if CPU0 is offline.
-* PIC interrupts. CPU0 can't be removed if a PIC interrupt is detected.
-
-Please let Fenghua Yu <fenghua.yu@intel.com> know if you find any dependencies
-on CPU0.
+The CPU is usable again. This should work on all CPUs, but CPU0 is often special
+and excluded from CPU hotplug.
The CPU hotplug coordination
============================