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authorSuzuki K Poulose <suzuki.poulose@arm.com>2016-07-21 11:15:27 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2016-07-21 16:48:37 +0100
commite75118a7b581b19b08282c7819c1ec6f68b91b79 (patch)
treeb2f9b83d8f4627a243c20001ec064e27aad10a01 /arch/arm64
parent9113c2aa05e9848cd4f1154abee17d4f265f012d (diff)
downloadlinux-e75118a7b581b19b08282c7819c1ec6f68b91b79.tar.bz2
arm64: Honor nosmp kernel command line option
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: <stable@vger.kernel.org> # 4.7+ Cc: Will Deacon <will.deacon@arm.com> Cc: James Morse <james.morse@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.com> [catalin.marinas@arm.com: updated code comment] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kernel/smp.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 298dd745651e..490db85dec23 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -693,6 +693,13 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
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.