On Tue, 07 Nov 2023 10:30:25 +0000
Russell King <rmk+kernel@xxxxxxxxxxxxxxx> 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>
Given this series adds an arch_cpu_is_hotpluggable() callback we probably
want something in this patch description to say why this
isn't using that, but instead overriding arch_register_cpu()
Jonathan
> ---
> 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 7b071a00425d..84bce830e365 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 f3034099fd95..b1e43f56ee46 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)
> {
