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Date:   Thu, 11 Apr 2019 00:01:19 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Atish Patra <atish.patra@wdc.com>
Cc:     linux-kernel@vger.kernel.org, Albert Ou <aou@eecs.berkeley.edu>,
        Andreas Schwab <schwab@suse.de>,
        Anup Patel <anup@brainfault.org>,
        Dmitriy Cherkasov <dmitriy@oss-tech.org>,
        Johan Hovold <johan@kernel.org>,
        linux-riscv@lists.infradead.org,
        Palmer Dabbelt <palmer@sifive.com>,
        Paul Walmsley <paul.walmsley@sifive.com>
Subject: Re: [PATCH v2 3/4] RISC-V: Implement nosmp commandline option.
Message-ID: <20190411070119.GD29422@infradead.org>
References: <20190410230443.15729-1-atish.patra@wdc.com>
 <20190410230443.15729-4-atish.patra@wdc.com>
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On Wed, Apr 10, 2019 at 04:04:42PM -0700, Atish Patra wrote:
> nosmp command line option sets max_cpus to zero. No secondary harts
> will boot if this is enabled. But present cpu mask will still point to
> all possible masks.
> 
> Fix present cpu mask for nosmp usecase.
> 
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> ---
>  arch/riscv/kernel/smpboot.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index eb533b5c2c8c..a8ad200581aa 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -47,6 +47,17 @@ void __init smp_prepare_boot_cpu(void)
>  
>  void __init smp_prepare_cpus(unsigned int max_cpus)
>  {
> +	int cpuid;
> +
> +	/* This covers non-smp usecase mandated by "nosmp" option */
> +	if (max_cpus == 0)
> +		return;
> +
> +	for_each_possible_cpu(cpuid) {
> +		if (cpuid == smp_processor_id())
> +			continue;
> +		set_cpu_present(cpuid, true);
> +	}

Most other architectures seem to use init_cpu_present() here.

Otherwise this looks fine to me.