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arm64: smp: Do not mark secondary CPUs possible under nosmp

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Under nosmp (maxcpus=0), arm64 never brings up secondary CPUs.

smp_prepare_cpus() already treats this as a UP-mandated boot and returns
before marking secondary CPUs present. However, smp_init_cpus() may still
enumerate firmware-described secondary CPUs and mark them possible before
that point.

Avoid marking secondary CPUs possible when nosmp/maxcpus=0 is in effect,
so that cpu_possible_mask reflects the nosmp boot policy for this boot.

Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Pengjie Zhang 2026-05-06 17:08:51 +08:00 committed by Will Deacon
parent 827ce94e08
commit e7cec385d2
1 changed files with 10 additions and 4 deletions
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14
arch/arm64/kernel/smp.c
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@ -745,15 +745,21 @@ void __init smp_init_cpus(void)
else
acpi_parse_and_init_cpus();
if (cpu_count > nr_cpu_ids)
pr_warn("Number of cores (%d) exceeds configured maximum of %u - clipping\n",
cpu_count, nr_cpu_ids);
if (!bootcpu_valid) {
pr_err("missing boot CPU MPIDR, not enabling secondaries\n");
return;
}
/*
* For the nosmp/maxcpus=0 case, do not mark the secondary CPUs
* possible.
*/
if (!setup_max_cpus)
return;
if (cpu_count > nr_cpu_ids)
pr_warn("Number of cores (%d) exceeds configured maximum of %u - clipping\n",
cpu_count, nr_cpu_ids);
/*
* We need to set the cpu_logical_map entries before enabling
* the cpus so that cpu processor description entries (DT cpu nodes