[PATCH 11/39] arm64: setup: Switch over to GENERIC_CPU_DEVICES using arch_register_cpu()

Russell King
2023-10-24T15:18:31Z

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@arm.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
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(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 78f20e632712..4042cd6fc6b2 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -132,6 +132,7 @@ config ARM64
select GENERIC_ARCH_TOPOLOGY
select GENERIC_CLOCKEVENTS_BROADCAST
select GENERIC_CPU_AUTOPROBE
+ select GENERIC_CPU_DEVICES
select GENERIC_CPU_VULNERABILITIES
select GENERIC_EARLY_IOREMAP
select GENERIC_IDLE_POLL_SETUP
diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
index e749838b9c5d..887bd0d992bb 100644
--- a/arch/arm64/include/asm/cpu.h
+++ b/arch/arm64/include/asm/cpu.h
@@ -38,7 +38,6 @@ struct cpuinfo_32bit {
};

struct cpuinfo_arm64 {
- struct cpu cpu;
struct kobject kobj;
u64 reg_ctr;
u64 reg_cntfrq;
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 417a8a86b2db..165bd2c0dd5a 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -402,19 +402,14 @@ static inline bool cpu_can_disable(unsigned int cpu)
return false;
}

-static int __init topology_init(void)
+int arch_register_cpu(int num)
{
- int i;
+ struct cpu *cpu = &per_cpu(cpu_devices, num);

- for_each_possible_cpu(i) {
- struct cpu *cpu = &per_cpu(cpu_data.cpu, i);
- cpu->hotpluggable = cpu_can_disable(i);
- register_cpu(cpu, i);
- }
+ cpu->hotpluggable = cpu_can_disable(num);

- return 0;
+ return register_cpu(cpu, num);
}
-subsys_initcall(topology_init);

static void dump_kernel_offset(void)
{
--
2.30.2