The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Thanks, Sasha
------------------ original commit in Linus's tree ------------------
From 777f81f0a9c780a6443bcf2c7785f0cc2e87c1ef Mon Sep 17 00:00:00 2001 From: Michael Ellerman mpe@ellerman.id.au Date: Thu, 15 Feb 2024 00:14:04 +1100 Subject: [PATCH] powerpc/smp: Increase nr_cpu_ids to include the boot CPU
If nr_cpu_ids is too low to include the boot CPU adjust nr_cpu_ids upward. Otherwise the kernel will BUG when trying to allocate a paca for the boot CPU and fail to boot.
Cc: stable@vger.kernel.org Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://msgid.link/20231229120107.2281153-2-mpe@ellerman.id.au --- arch/powerpc/kernel/prom.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c index 58e80076bed5c..77364729a1b61 100644 --- a/arch/powerpc/kernel/prom.c +++ b/arch/powerpc/kernel/prom.c @@ -381,6 +381,12 @@ static int __init early_init_dt_scan_cpus(unsigned long node, nr_cpu_ids); }
+ if (boot_cpuid >= nr_cpu_ids) { + set_nr_cpu_ids(min(CONFIG_NR_CPUS, ALIGN(boot_cpuid + 1, nthreads))); + pr_warn("Boot CPU %d >= nr_cpu_ids, adjusted nr_cpu_ids to %d\n", + boot_cpuid, nr_cpu_ids); + } + /* * PAPR defines "logical" PVR values for cpus that * meet various levels of the architecture: