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

[Jinjie Ruan]

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(-)

-- 
2.34.1