This is a note to let you know that I've just added the patch titled
arm64: Honor nosmp kernel command line option
to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-honor-nosmp-kernel-command-line-option.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e75118a7b581b19b08282c7819c1ec6f68b91b79 Mon Sep 17 00:00:00 2001
From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Date: Thu, 21 Jul 2016 11:15:27 +0100
Subject: arm64: Honor nosmp kernel command line option
From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
commit e75118a7b581b19b08282c7819c1ec6f68b91b79 upstream.
Passing "nosmp" should boot the kernel with a single processor, without
provision to enable secondary CPUs even if they are present. "nosmp" is
implemented by setting maxcpus=0. At the moment we still mark the secondary
CPUs present even with nosmp, which allows the userspace to bring them
up. This patch corrects the smp_prepare_cpus() to honor the maxcpus == 0.
Commit 44dbcc93ab67145 ("arm64: Fix behavior of maxcpus=N") fixed the
behavior for maxcpus >= 1, but broke maxcpus = 0.
Fixes: 44dbcc93ab67 ("arm64: Fix behavior of maxcpus=N")
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
[catalin.marinas@xxxxxxx: updated code comment]
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/smp.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -693,6 +693,13 @@ void __init smp_prepare_cpus(unsigned in
smp_store_cpu_info(smp_processor_id());
/*
+ * If UP is mandated by "nosmp" (which implies "maxcpus=0"), don't set
+ * secondary CPUs present.
+ */
+ if (max_cpus == 0)
+ return;
+
+ /*
* Initialise the present map (which describes the set of CPUs
* actually populated at the present time) and release the
* secondaries from the bootloader.
Patches currently in stable-queue which might be from suzuki.poulose@xxxxxxx are
queue-4.7/arm64-fix-incorrect-per-cpu-usage-for-boot-cpu.patch
queue-4.7/arm64-honor-nosmp-kernel-command-line-option.patch
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