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Date:   Thu, 30 Aug 2018 23:18:59 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Atish Patra <atish.patra@wdc.com>
Cc:     palmer@sifive.com, linux-riscv@lists.infradead.org,
        mark.rutland@arm.com, anup@brainfault.org, hch@infradead.org,
        tglx@linutronix.de, linux-kernel@vger.kernel.org,
        damein@vger.kernel.org
Subject: Re: [PATCH v2 3/3] RISC-V: Support cpu hotplug.
Message-ID: <20180831061859.GC19292@infradead.org>
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> +#else
> +static inline bool can_hotplug_cpu(void) { return 0; }
> +static inline void arch_send_call_wakeup_ipi(int cpu) { }

Please use normal coding style for these stubs.

>  #define INTERRUPT_CAUSE_FLAG	(1UL << (__riscv_xlen - 1))
> +#define get_scause(cause)	(cause & ~INTERRUPT_CAUSE_FLAG)

I think this helper is misleading - the cause includes the interrupt
flag.  I'd rather open code this in the other place as well.

> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index d7c6ca7c..cb209139 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -42,6 +42,13 @@ void arch_cpu_idle(void)
>  	local_irq_enable();
>  }
>  
> +#ifdef CONFIG_HOTPLUG_CPU
> +void arch_cpu_idle_dead(void)
> +{
> +	cpu_play_dead();
> +}
> +#endif

I wonder if it might be worth to introduce a small
arch/riscv/kernel/cpu-hotplug.c file for the various CONFIG_HOTPLUG_CPU
only functions.