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

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On 11/7/23 18:30, 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>
Reviewed-by: Shaoqin Huang <shahuang@xxxxxxxxxx>
---
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)
  {

--
Shaoqin




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