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From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
	Thomas Gleixner <tglx@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Borislav Petkov <bp@alien8.de>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Jinjie Ruan <ruanjinjie@huawei.com>,
	Mark Rutland <mark.rutland@arm.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Peter Zijlstra <peterz@infradead.org>,
	Marc Zyngier <maz@kernel.org>
Subject: [PATCH 05/19] arm64: smp: Tidy up smp_prepare_cpus()
Date: Mon,  7 Sep 2026 17:40:08 +0100	[thread overview]
Message-ID: <20260907164024.17164-6-will@kernel.org> (raw)
In-Reply-To: <20260907164024.17164-1-will@kernel.org>

smp_prepare_cpus() is always run on the boot CPU (i.e. CPU 0) but goes
to great lengths to support running on a CPU where smp_processor_id()
is non-zero.

Clean up the code a little by hardcoding zero for the boot CPU ID.

Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/smp.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index a61dc3016a11..ff045080ca1b 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -779,16 +779,14 @@ void __init smp_init_cpus(void)
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
 	const struct cpu_operations *ops;
-	int err;
 	unsigned int cpu;
-	unsigned int this_cpu;
+	int err;
 
 	init_cpu_topology();
 
-	this_cpu = smp_processor_id();
-	store_cpu_topology(this_cpu);
-	numa_store_cpu_info(this_cpu);
-	numa_add_cpu(this_cpu);
+	store_cpu_topology(0);
+	numa_store_cpu_info(0);
+	numa_add_cpu(0);
 
 	/*
 	 * If UP is mandated by "nosmp" (which implies "maxcpus=0"), don't set
@@ -803,8 +801,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 	 * secondaries from the bootloader.
 	 */
 	for_each_possible_cpu(cpu) {
-
-		if (cpu == smp_processor_id())
+		if (cpu == 0)
 			continue;
 
 		ops = get_cpu_ops(cpu);
-- 
2.55.0.979.g7e5102b832-goog



  parent reply	other threads:[~2026-09-07 16:41 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-07 16:40 [PATCH 00/19] arm64: Implement parallel CPU onlining with PSCI v0.2+ Will Deacon
2026-09-07 16:40 ` [PATCH 01/19] cpu/hotplug: Clean up cmpxchg() logic in cpuhp_can_boot_ap() Will Deacon
2026-09-08  2:55   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 02/19] cpu/hotplug: Avoid trying to bring up CPUs that are already online Will Deacon
2026-09-08  3:13   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 03/19] cpu/hotplug: Avoid busy-polling on archs where cpu_relax() is a no-op Will Deacon
2026-09-08  4:00   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 04/19] cpu/hotplug: Propagate bring-up status to arch_cpuhp_cleanup_kick_cpu() Will Deacon
2026-09-08  4:05   ` Jinjie Ruan
2026-09-07 16:40 ` Will Deacon [this message]
2026-09-08  7:35   ` [PATCH 05/19] arm64: smp: Tidy up smp_prepare_cpus() Jinjie Ruan
2026-09-07 16:40 ` [PATCH 06/19] arm64: smp: Tidy up cpuinfo init and cpufeature updates Will Deacon
2026-09-08  7:53   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 07/19] arm64: smp: Defer update of secondary CPU capabilities Will Deacon
2026-09-08  8:20   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 08/19] arm64: smp: Don't bother printing the I-cache policy for each CPU Will Deacon
2026-09-08  8:33   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 09/19] arm64: smp: Defer RCU registration during secondary CPU bringup Will Deacon
2026-09-08  8:55   ` Jinjie Ruan
2026-09-08 10:19     ` Will Deacon
2026-09-08 11:25       ` Jinjie Ruan
2026-09-09 12:36         ` Will Deacon
2026-09-10  2:47           ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 10/19] arm64: smp: Use generic HOTPLUG_CORE_SYNC_FULL machinery for CPU onlining Will Deacon
2026-09-08  9:01   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 11/19] arm64: smp: Use generic HOTPLUG_SPLIT_STARTUP " Will Deacon
2026-09-08  9:10   ` Jinjie Ruan
2026-09-08 11:35   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 12/19] arm64: cpu_ops: Make 'cpu_operations' pointer global instead of per-cpu Will Deacon
2026-09-08 11:32   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 13/19] arm64: cpu_ops: Introduce get_secondary_cpu_ops() Will Deacon
2026-09-08 11:56   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 14/19] firmware/psci: Cache PSCI v0.2+ version number to avoid redundant SMCs Will Deacon
2026-09-08 11:57   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 15/19] firmware/psci: Extend ->cpu_on() callback to take an additional argument Will Deacon
2026-09-08 12:05   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 16/19] arm64: cpu_ops: Expose optional argument to target cpu in ->cpu_boot() Will Deacon
2026-09-08 12:12   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 17/19] arm64: smp: Pass secondary CPU boot parameters via firmware if possible Will Deacon
2026-09-08 12:16   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 18/19] arm64: smp: Use generic HOTPLUG_PARALLEL machinery for CPU onlining Will Deacon
2026-09-08 13:05   ` Jinjie Ruan
2026-09-07 16:40 ` [PATCH 19/19] arm64: smp: Harden parallel CPU bringup against broken PSCI firmware Will Deacon
2026-09-08 13:36   ` Will Deacon

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