Re: [PATCH RFC 13/22] arm64: setup: Switch over to GENERIC_CPU_DEVICES using arch_register_cpu()

From: Gavin Shan
Date: Sun Nov 12 2023 - 23:08:34 EST


On 11/7/23 20:30, Russell King (Oracle) wrote:
From: James Morse <james.morse@xxxxxxx>

To allow ACPI's _STA value to hide CPUs that are present, but not
available to online right now due to VMM or firmware policy, the
register_cpu() call needs to be made by the ACPI machinery when ACPI
is in use. This allows it to hide CPUs that are unavailable from sysfs.

Switching to GENERIC_CPU_DEVICES is an intermediate step to allow all
five ACPI architectures to be modified at once.

Switch over to GENERIC_CPU_DEVICES, and provide an arch_register_cpu()
that populates the hotpluggable flag. arch_register_cpu() is also the
interface the ACPI machinery expects.

The struct cpu in struct cpuinfo_arm64 is never used directly, remove
it to use the one GENERIC_CPU_DEVICES provides.

This changes the CPUs visible in sysfs from possible to present, but
on arm64 smp_prepare_cpus() ensures these are the same.

This patch also has the effect of moving the registration of CPUs from
subsys to driver core initialisation, prior to any initcalls running.

Signed-off-by: James Morse <james.morse@xxxxxxx>
Reviewed-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
---
Changes since RFC v2:
* Add note about initialisation order change.
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/cpu.h | 1 -
arch/arm64/kernel/setup.c | 13 ++++---------
3 files changed, 5 insertions(+), 10 deletions(-)


Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>