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[RFC,v2,03/35] drivers: base: Allow parts of GENERIC_CPU_DEVICES to be overridden

Message ID 20230913163823.7880-4-james.morse@arm.com (mailing list archive)
State Handled Elsewhere
Headers show
Series ACPI/arm64: add support for virtual cpuhotplug | expand

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Commit Message

James Morse Sept. 13, 2023, 4:37 p.m. UTC
Architectures often have extra per-cpu work that needs doing
before a CPU is registered, often to determine if a CPU is
hotpluggable.

To allow the ACPI architectures to use GENERIC_CPU_DEVICES, move
the cpu_register() call into arch_register_cpu(), which is made __weak
so architectures with extra work can override it.
This aligns with the way x86, ia64 and loongarch register hotplug CPUs
when they become present.

Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since RFC:
 * Dropped __init from x86/ia64 arch_register_cpu()
---
 arch/ia64/include/asm/cpu.h      |  1 -
 arch/ia64/kernel/topology.c      |  2 +-
 arch/loongarch/include/asm/cpu.h |  1 -
 arch/x86/include/asm/cpu.h       |  1 -
 arch/x86/kernel/topology.c       |  2 +-
 drivers/base/cpu.c               | 14 ++++++++++----
 include/linux/cpu.h              |  5 +++++
 7 files changed, 17 insertions(+), 9 deletions(-)

Comments

Russell King (Oracle) Sept. 14, 2023, 8:33 a.m. UTC | #1
On Wed, Sep 13, 2023 at 04:37:51PM +0000, James Morse wrote:
> Architectures often have extra per-cpu work that needs doing
> before a CPU is registered, often to determine if a CPU is
> hotpluggable.
> 
> To allow the ACPI architectures to use GENERIC_CPU_DEVICES, move
> the cpu_register() call into arch_register_cpu(), which is made __weak
> so architectures with extra work can override it.
> This aligns with the way x86, ia64 and loongarch register hotplug CPUs
> when they become present.
> 
> Signed-off-by: James Morse <james.morse@arm.com>

LGTM.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Jonathan Cameron Sept. 14, 2023, 11 a.m. UTC | #2
On Wed, 13 Sep 2023 16:37:51 +0000
James Morse <james.morse@arm.com> wrote:

> Architectures often have extra per-cpu work that needs doing
> before a CPU is registered, often to determine if a CPU is
> hotpluggable.
> 
> To allow the ACPI architectures to use GENERIC_CPU_DEVICES, move
> the cpu_register() call into arch_register_cpu(), which is made __weak
> so architectures with extra work can override it.
> This aligns with the way x86, ia64 and loongarch register hotplug CPUs
> when they become present.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> Changes since RFC:
>  * Dropped __init from x86/ia64 arch_register_cpu()
Confused...

> diff --git a/arch/ia64/kernel/topology.c b/arch/ia64/kernel/topology.c
> index 94a848b06f15..741863a187a6 100644
> --- a/arch/ia64/kernel/topology.c
> +++ b/arch/ia64/kernel/topology.c
> @@ -59,7 +59,7 @@ void __ref arch_unregister_cpu(int num)
>  }
>  EXPORT_SYMBOL(arch_unregister_cpu);
>  #else
> -static int __init arch_register_cpu(int num)
> +int __init arch_register_cpu(int num)

Still seems to be here...

>  {
>  	return register_cpu(&sysfs_cpus[num].cpu, num);
>  }

Even more confused because the block wasn't in the RFC at all.
Maybe dropped static?
Jonathan Cameron Sept. 14, 2023, 11:05 a.m. UTC | #3
On Wed, 13 Sep 2023 16:37:51 +0000
James Morse <james.morse@arm.com> wrote:

> Architectures often have extra per-cpu work that needs doing
> before a CPU is registered, often to determine if a CPU is
> hotpluggable.
> 
> To allow the ACPI architectures to use GENERIC_CPU_DEVICES, move
> the cpu_register() call into arch_register_cpu(), which is made __weak
> so architectures with extra work can override it.
> This aligns with the way x86, ia64 and loongarch register hotplug CPUs
> when they become present.

Perhaps call out that you are also making cpu_devices visible outside
of base/cpu.c

Note it isn't obvious to me why you do that in this patch. I assume
it will be needed later...


Otherwise seems sensible to me.

> 
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> Changes since RFC:
>  * Dropped __init from x86/ia64 arch_register_cpu()
> ---
>  arch/ia64/include/asm/cpu.h      |  1 -
>  arch/ia64/kernel/topology.c      |  2 +-
>  arch/loongarch/include/asm/cpu.h |  1 -
>  arch/x86/include/asm/cpu.h       |  1 -
>  arch/x86/kernel/topology.c       |  2 +-
>  drivers/base/cpu.c               | 14 ++++++++++----
>  include/linux/cpu.h              |  5 +++++
>  7 files changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h
> index db125df9e088..a3e690e685e5 100644
> --- a/arch/ia64/include/asm/cpu.h
> +++ b/arch/ia64/include/asm/cpu.h
> @@ -16,7 +16,6 @@ DECLARE_PER_CPU(struct ia64_cpu, cpu_devices);
>  DECLARE_PER_CPU(int, cpu_state);
>  
>  #ifdef CONFIG_HOTPLUG_CPU
> -extern int arch_register_cpu(int num);
>  extern void arch_unregister_cpu(int);
>  #endif
>  
> diff --git a/arch/ia64/kernel/topology.c b/arch/ia64/kernel/topology.c
> index 94a848b06f15..741863a187a6 100644
> --- a/arch/ia64/kernel/topology.c
> +++ b/arch/ia64/kernel/topology.c
> @@ -59,7 +59,7 @@ void __ref arch_unregister_cpu(int num)
>  }
>  EXPORT_SYMBOL(arch_unregister_cpu);
>  #else
> -static int __init arch_register_cpu(int num)
> +int __init arch_register_cpu(int num)
>  {
>  	return register_cpu(&sysfs_cpus[num].cpu, num);
>  }
> diff --git a/arch/loongarch/include/asm/cpu.h b/arch/loongarch/include/asm/cpu.h
> index 7afe8cbb844e..b8568e637420 100644
> --- a/arch/loongarch/include/asm/cpu.h
> +++ b/arch/loongarch/include/asm/cpu.h
> @@ -130,7 +130,6 @@ enum cpu_type_enum {
>  
>  #if !defined(__ASSEMBLY__)
>  #ifdef CONFIG_HOTPLUG_CPU
> -int arch_register_cpu(int num);
>  void arch_unregister_cpu(int cpu);
>  #endif
>  #endif /* ! __ASSEMBLY__ */
> diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
> index 3a233ebff712..96dc4665e87d 100644
> --- a/arch/x86/include/asm/cpu.h
> +++ b/arch/x86/include/asm/cpu.h
> @@ -28,7 +28,6 @@ struct x86_cpu {
>  };
>  
>  #ifdef CONFIG_HOTPLUG_CPU
> -extern int arch_register_cpu(int num);
>  extern void arch_unregister_cpu(int);
>  extern void soft_restart_cpu(void);
>  #endif
> diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
> index ca004e2e4469..0bab03130033 100644
> --- a/arch/x86/kernel/topology.c
> +++ b/arch/x86/kernel/topology.c
> @@ -54,7 +54,7 @@ void arch_unregister_cpu(int num)
>  EXPORT_SYMBOL(arch_unregister_cpu);
>  #else /* CONFIG_HOTPLUG_CPU */
>  
> -static int __init arch_register_cpu(int num)
> +int __init arch_register_cpu(int num)
>  {
>  	return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
>  }
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 34b48f660b6b..579064fda97b 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -525,19 +525,25 @@ bool cpu_is_hotpluggable(unsigned int cpu)
>  EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
>  
>  #ifdef CONFIG_GENERIC_CPU_DEVICES
> -static DEFINE_PER_CPU(struct cpu, cpu_devices);
> +DEFINE_PER_CPU(struct cpu, cpu_devices);
> +
> +int __weak arch_register_cpu(int cpu)
> +{
> +	return register_cpu(&per_cpu(cpu_devices, cpu), cpu);
> +}
>  #endif
>  
>  static void __init cpu_dev_register_generic(void)
>  {
> -#ifdef CONFIG_GENERIC_CPU_DEVICES
>  	int i;
>  
> +	if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES))
> +		return;
> +
>  	for_each_present_cpu(i) {
> -		if (register_cpu(&per_cpu(cpu_devices, i), i))
> +		if (arch_register_cpu(i))
>  			panic("Failed to register CPU device");
>  	}
> -#endif
>  }
>  
>  #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index 0abd60a7987b..a71691d7c2ca 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -80,12 +80,17 @@ extern __printf(4, 5)
>  struct device *cpu_device_create(struct device *parent, void *drvdata,
>  				 const struct attribute_group **groups,
>  				 const char *fmt, ...);
> +extern int arch_register_cpu(int cpu);
>  #ifdef CONFIG_HOTPLUG_CPU
>  extern void unregister_cpu(struct cpu *cpu);
>  extern ssize_t arch_cpu_probe(const char *, size_t);
>  extern ssize_t arch_cpu_release(const char *, size_t);
>  #endif
>  
> +#ifdef CONFIG_GENERIC_CPU_DEVICES
> +DECLARE_PER_CPU(struct cpu, cpu_devices);
> +#endif
> +
>  /*
>   * These states are not related to the core CPU hotplug mechanism. They are
>   * used by various (sub)architectures to track internal state
diff mbox series

Patch

diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h
index db125df9e088..a3e690e685e5 100644
--- a/arch/ia64/include/asm/cpu.h
+++ b/arch/ia64/include/asm/cpu.h
@@ -16,7 +16,6 @@  DECLARE_PER_CPU(struct ia64_cpu, cpu_devices);
 DECLARE_PER_CPU(int, cpu_state);
 
 #ifdef CONFIG_HOTPLUG_CPU
-extern int arch_register_cpu(int num);
 extern void arch_unregister_cpu(int);
 #endif
 
diff --git a/arch/ia64/kernel/topology.c b/arch/ia64/kernel/topology.c
index 94a848b06f15..741863a187a6 100644
--- a/arch/ia64/kernel/topology.c
+++ b/arch/ia64/kernel/topology.c
@@ -59,7 +59,7 @@  void __ref arch_unregister_cpu(int num)
 }
 EXPORT_SYMBOL(arch_unregister_cpu);
 #else
-static int __init arch_register_cpu(int num)
+int __init arch_register_cpu(int num)
 {
 	return register_cpu(&sysfs_cpus[num].cpu, num);
 }
diff --git a/arch/loongarch/include/asm/cpu.h b/arch/loongarch/include/asm/cpu.h
index 7afe8cbb844e..b8568e637420 100644
--- a/arch/loongarch/include/asm/cpu.h
+++ b/arch/loongarch/include/asm/cpu.h
@@ -130,7 +130,6 @@  enum cpu_type_enum {
 
 #if !defined(__ASSEMBLY__)
 #ifdef CONFIG_HOTPLUG_CPU
-int arch_register_cpu(int num);
 void arch_unregister_cpu(int cpu);
 #endif
 #endif /* ! __ASSEMBLY__ */
diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index 3a233ebff712..96dc4665e87d 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -28,7 +28,6 @@  struct x86_cpu {
 };
 
 #ifdef CONFIG_HOTPLUG_CPU
-extern int arch_register_cpu(int num);
 extern void arch_unregister_cpu(int);
 extern void soft_restart_cpu(void);
 #endif
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index ca004e2e4469..0bab03130033 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -54,7 +54,7 @@  void arch_unregister_cpu(int num)
 EXPORT_SYMBOL(arch_unregister_cpu);
 #else /* CONFIG_HOTPLUG_CPU */
 
-static int __init arch_register_cpu(int num)
+int __init arch_register_cpu(int num)
 {
 	return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
 }
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 34b48f660b6b..579064fda97b 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -525,19 +525,25 @@  bool cpu_is_hotpluggable(unsigned int cpu)
 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 
 #ifdef CONFIG_GENERIC_CPU_DEVICES
-static DEFINE_PER_CPU(struct cpu, cpu_devices);
+DEFINE_PER_CPU(struct cpu, cpu_devices);
+
+int __weak arch_register_cpu(int cpu)
+{
+	return register_cpu(&per_cpu(cpu_devices, cpu), cpu);
+}
 #endif
 
 static void __init cpu_dev_register_generic(void)
 {
-#ifdef CONFIG_GENERIC_CPU_DEVICES
 	int i;
 
+	if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES))
+		return;
+
 	for_each_present_cpu(i) {
-		if (register_cpu(&per_cpu(cpu_devices, i), i))
+		if (arch_register_cpu(i))
 			panic("Failed to register CPU device");
 	}
-#endif
 }
 
 #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 0abd60a7987b..a71691d7c2ca 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -80,12 +80,17 @@  extern __printf(4, 5)
 struct device *cpu_device_create(struct device *parent, void *drvdata,
 				 const struct attribute_group **groups,
 				 const char *fmt, ...);
+extern int arch_register_cpu(int cpu);
 #ifdef CONFIG_HOTPLUG_CPU
 extern void unregister_cpu(struct cpu *cpu);
 extern ssize_t arch_cpu_probe(const char *, size_t);
 extern ssize_t arch_cpu_release(const char *, size_t);
 #endif
 
+#ifdef CONFIG_GENERIC_CPU_DEVICES
+DECLARE_PER_CPU(struct cpu, cpu_devices);
+#endif
+
 /*
  * These states are not related to the core CPU hotplug mechanism. They are
  * used by various (sub)architectures to track internal state