Re: [patch 05/37] x86/topology: Remove CPU0 hotplug option

Paul E. McKenney
2023-06-21T16:51:22Z

On Sat, Apr 15, 2023 at 01:44:21AM +0200, Thomas Gleixner wrote:
> 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>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 14 ---
> Documentation/core-api/cpu_hotplug.rst | 13 ---
> arch/x86/Kconfig | 43 ----------
> arch/x86/include/asm/cpu.h | 3
> arch/x86/kernel/topology.c | 98 ------------------------
> arch/x86/power/cpu.c | 37 ---------
> 6 files changed, 6 insertions(+), 202 deletions(-)

[ . . . ]

> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2294,49 +2294,6 @@ config HOTPLUG_CPU
> def_bool y
> depends on SMP
>
> -config BOOTPARAM_HOTPLUG_CPU0

Removing this requires also removing its use in rcutorture.

I have therefore queued the commit below in -rcu, but please feel
free to take it along with the BOOTPARAM_HOTPLUG_CPU0-removal patch.
Just please let me know if you do.

(Yes, I finally got back to testing -next. Why do you ask?)

Thanx, Paul

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

commit 95588de780c0e81004b72526aa3e3ef5ce054719
Author: Paul E. McKenney <paulmck@kernel.org>
Date: Wed Jun 21 09:44:52 2023 -0700

rcutorture: Remove obsolete BOOTPARAM_HOTPLUG_CPU0 Kconfig option

Now that the BOOTPARAM_HOTPLUG_CPU0 Kconfig option is in the process of
being removed, it is time to remove rcutorture's use of it.

Link: https://lore.kernel.org/lkml/20230414232309.510911744@linutronix.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <x86@kernel.org>

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE01 b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
index 04831ef1f9b5..8ae41d5f81a3 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
@@ -15,4 +15,3 @@ CONFIG_DEBUG_LOCK_ALLOC=n
CONFIG_RCU_BOOST=n
CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
CONFIG_RCU_EXPERT=y
-CONFIG_BOOTPARAM_HOTPLUG_CPU0=y