linux-kernel - [PATCH 14/21] x86/topology: Switch over to GENERIC_CPU

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Message-Id: <E1r5R3l-00Cszm-UA@rmk-PC.armlinux.org.uk>
Date:   Tue, 21 Nov 2023 13:45:01 +0000
From:   Russell King (Oracle) <rmk+kernel@...linux.org.uk>
To:     linux-pm@...r.kernel.org, loongarch@...ts.linux.dev,
        linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev,
        x86@...nel.org, linux-csky@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-parisc@...r.kernel.org
Cc:     Salil Mehta <salil.mehta@...wei.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        jianyong.wu@....com, justin.he@....com,
        James Morse <james.morse@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 14/21] x86/topology: Switch over to GENERIC_CPU_DEVICES

From: James Morse <james.morse@....com>

Now that GENERIC_CPU_DEVICES calls arch_register_cpu(), which can be
overridden by the arch code, switch over to this to allow common code
to choose when the register_cpu() call is made.

x86's struct cpus come from struct x86_cpu, which has no other members
or users. Remove this and use the version defined by common code.

This is an intermediate step to the logic being moved to drivers/acpi,
where GENERIC_CPU_DEVICES will do the work when booting with acpi=off.

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@....com>
Reviewed-by: Gavin Shan <gshan@...hat.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
----
Changes since RFC:
 * Fixed the second copy of arch_register_cpu() used for non-hotplug
Changes since RFC v2:
 * Remove duplicate of the weak generic arch_register_cpu(), spotted
   by Jonathan Cameron. Add note about initialisation order change.
Changes since RFC v3:
 * Adapt to removal of EXPORT_SYMBOL()s
---
 arch/x86/Kconfig           |  1 +
 arch/x86/include/asm/cpu.h |  4 ----
 arch/x86/kernel/topology.c | 27 ++++-----------------------
 3 files changed, 5 insertions(+), 27 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index dbdcfc708369..8330c4ac26b3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -148,6 +148,7 @@ config X86
 	select GENERIC_CLOCKEVENTS_MIN_ADJUST
 	select GENERIC_CMOS_UPDATE
 	select GENERIC_CPU_AUTOPROBE
+	select GENERIC_CPU_DEVICES
 	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_ENTRY
diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index fecc4fe1d68a..f8f9a9b79395 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -23,10 +23,6 @@ static inline void prefill_possible_map(void) {}
 
 #endif /* CONFIG_SMP */
 
-struct x86_cpu {
-	struct cpu cpu;
-};
-
 #ifdef CONFIG_HOTPLUG_CPU
 extern void soft_restart_cpu(void);
 #endif
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index fcb62cfdf946..c2ed3145a93b 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -35,36 +35,17 @@
 #include <asm/io_apic.h>
 #include <asm/cpu.h>
 
-static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
-
 #ifdef CONFIG_HOTPLUG_CPU
 int arch_register_cpu(int cpu)
 {
-	struct x86_cpu *xc = per_cpu_ptr(&cpu_devices, cpu);
+	struct cpu *c = per_cpu_ptr(&cpu_devices, cpu);
 
-	xc->cpu.hotpluggable = cpu > 0;
-	return register_cpu(&xc->cpu, cpu);
+	c->hotpluggable = cpu > 0;
+	return register_cpu(c, cpu);
 }
 
 void arch_unregister_cpu(int num)
 {
-	unregister_cpu(&per_cpu(cpu_devices, num).cpu);
-}
-#else /* CONFIG_HOTPLUG_CPU */
-
-int __init arch_register_cpu(int num)
-{
-	return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
+	unregister_cpu(&per_cpu(cpu_devices, num));
 }
 #endif /* CONFIG_HOTPLUG_CPU */
-
-static int __init topology_init(void)
-{
-	int i;
-
-	for_each_present_cpu(i)
-		arch_register_cpu(i);
-
-	return 0;
-}
-subsys_initcall(topology_init);
-- 
2.30.2