linux-kernel - FAILED: Patch "powerpc/smp: Adjust nr_cpu_ids to cover all threads of a core" failed to apply to 4.19-stable tree

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Message-ID: <20240327122657.2841493-1-sashal@kernel.org>
Date: Wed, 27 Mar 2024 08:26:57 -0400
From: Sasha Levin <sashal@...nel.org>
To: stable@...r.kernel.org,
	mpe@...erman.id.au
Cc: linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: FAILED: Patch "powerpc/smp: Adjust nr_cpu_ids to cover all threads of a core" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-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@...r.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

>From 5580e96dad5a439d561d9648ffcbccb739c2a120 Mon Sep 17 00:00:00 2001
From: Michael Ellerman <mpe@...erman.id.au>
Date: Thu, 15 Feb 2024 00:14:04 +1100
Subject: [PATCH] powerpc/smp: Adjust nr_cpu_ids to cover all threads of a core

If nr_cpu_ids is too low to include at least all the threads of a single
core adjust nr_cpu_ids upwards. This avoids triggering odd bugs in code
that assumes all threads of a core are available.

Cc: stable@...r.kernel.org
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://msgid.link/20231229120107.2281153-1-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 0b5878c3125b1..58e80076bed5c 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -375,6 +375,12 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
 	if (IS_ENABLED(CONFIG_PPC64))
 		boot_cpu_hwid = be32_to_cpu(intserv[found_thread]);
 
+	if (nr_cpu_ids % nthreads != 0) {
+		set_nr_cpu_ids(ALIGN(nr_cpu_ids, nthreads));
+		pr_warn("nr_cpu_ids was not a multiple of threads_per_core, adjusted to %d\n",
+			nr_cpu_ids);
+	}
+
 	/*
 	 * PAPR defines "logical" PVR values for cpus that
 	 * meet various levels of the architecture:
-- 
2.43.0