Messages in this thread Patch in this message | | | From | Suzuki K Poulose <> | Subject | [PATCH] [4.7] arm64: Honor nosmp kernel command line option | Date | Thu, 21 Jul 2016 11:15:27 +0100 |
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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: commit 44dbcc93ab67145 ("arm64: Fix behavior of maxcpus=N") Cc: Will Deacon <will.deacon@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: James Morse <james.morse@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> --- arch/arm64/kernel/smp.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index d242e81..ec08b7a 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -694,6 +694,13 @@ void __init smp_prepare_cpus(unsigned int max_cpus) smp_store_cpu_info(smp_processor_id()); /* + * If UP is mandated by "nosmp"(implies maxcpus=0), don't bother about + * secondary CPUs. + */ + 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. -- 2.7.4
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