On Thu, Jul 21, 2016 at 11:15:27AM +0100, Suzuki K Poulose wrote:
> 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 <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Cc: James Morse <[email protected]>
> Signed-off-by: Suzuki K Poulose <[email protected]>
> ---
> 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
Nit: missing space between the quote abnd opening bracket. It would also
be nicer to have s/implies/which implies/
Otherwise:
Acked-by: Mark Rutland <[email protected]>
Mark.
> + * 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
>
