[PATCH v2 0/4] arm64: Add HOTPLUG_PARALLEL support for secondary CPUs

[Jinjie Ruan]

Please ignore this patchset, will update in v3.

On 6/18/2026 5:24 PM, Jinjie Ruan wrote:
> Support for parallel secondary CPU bringup is already utilized by x86,
> MIPS, and RISC-V. This patch brings this capability to the arm64
> architecture.
> 
> Introduce CONFIG_PARALLEL_SMT_PRIMARY_FIRST to avoid primary SMT threads
> to boot first constraint.
> 
> And Add a 'cpu' parameter to update_cpu_boot_status() to allow updating the
> boot status at a per-CPU granularity during parallel bringup.
> 
> Rework the global `secondary_data` accessed during early boot into
> a per-CPU array `cpu_boot_data` to allow secondary CPUs to boot
> in parallel.
> 
> And reuse `__cpu_logical_map` array in the early boot code in head.S
> to resolve each secondary CPU's logical ID concurrently.
> 
> Changes in v2:
> - Remove RFC.
> - Add Tested-by.
> - Fix AI review issues in [1].
> - Add arch_cpuhp_init_parallel_bringup() to check psci boot.
> - Reuse `__cpu_logical_map` instead of a new aray.
> - Defer rcutree_report_cpu_starting() until after
>   check_local_cpu_capabilities() to prevent a potential control CPU
>   deadlock if an early capability check fails.
> - Move the assembly in head.S to a macro called `mpidr_to_cpuid`.
> - Add `SECONDARY_DATA_SHIFT` for `lsl` to access `cpu_boot_data`.
> - Add sizeof(struct secondary_data) power of 2 assert check.
> - Expand testing with more data collected from real hardware.
> 
> [1] https://sashiko.dev/#/patchset/20260611133809.3854977-1-ruanjinjie%40huawei.com
> 
> Jinjie Ruan (4):
>   cpu/hotplug: Introduce CONFIG_PARALLEL_SMT_PRIMARY_FIRST
>   arm64: smp: Pass CPU ID to update_cpu_boot_status()
>   arm64: smp: Defer RCU reporting until after local CPU capability
>     checks
>   arm64: Add HOTPLUG_PARALLEL support for secondary CPUs
> 
>  arch/Kconfig                    |  4 +++
>  arch/arm64/Kconfig              |  1 +
>  arch/arm64/include/asm/smp.h    | 17 ++++++++++---
>  arch/arm64/kernel/asm-offsets.c |  4 +++
>  arch/arm64/kernel/cpufeature.c  | 22 ++++++++--------
>  arch/arm64/kernel/head.S        | 36 ++++++++++++++++++++++++++
>  arch/arm64/kernel/smp.c         | 45 ++++++++++++++++++++++++++++-----
>  arch/arm64/mm/context.c         |  4 +--
>  arch/mips/Kconfig               |  1 +
>  arch/riscv/Kconfig              |  1 +
>  arch/x86/Kconfig                |  1 +
>  kernel/cpu.c                    |  6 ++++-
>  12 files changed, 119 insertions(+), 23 deletions(-)
>