linux-kernel - Re: [RFC 5/6] RISC-V: Move spinwait booting method to its own config

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Date:   Fri, 3 Dec 2021 16:40:26 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Atish Patra <atishp@...shpatra.org>, linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...osinc.com>, Alexandre Ghiti <alex@...ti.fr>,
        Anup Patel <anup.patel@....com>,
        Greentime Hu <greentime.hu@...ive.com>,
        Guo Ren <guoren@...ux.alibaba.com>,
        Heinrich Schuchardt <xypron.glpk@....de>,
        Ingo Molnar <mingo@...nel.org>,
        Jisheng Zhang <jszhang@...nel.org>,
        kvm-riscv@...ts.infradead.org, kvm@...r.kernel.org,
        linux-riscv@...ts.infradead.org, Marc Zyngier <maz@...nel.org>,
        Nanyong Sun <sunnanyong@...wei.com>,
        Nick Kossifidis <mick@....forth.gr>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Pekka Enberg <penberg@...nel.org>,
        Vincent Chen <vincent.chen@...ive.com>,
        Vitaly Wool <vitaly.wool@...sulko.com>
Subject: Re: [RFC 5/6] RISC-V: Move spinwait booting method to its own config

Hi--

On 12/3/21 16:20, Atish Patra wrote:
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 821252b65f89..4afb42d5707d 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -403,6 +403,20 @@ config RISCV_SBI_V01
>  	  This config allows kernel to use SBI v0.1 APIs. This will be
>  	  deprecated in future once legacy M-mode software are no longer in use.
>  
> +config RISCV_BOOT_SPINWAIT
> +	bool "Spinwait booting method"
> +	depends on SMP
> +	default y
> +	help
> +	  This enables support for booting Linux via spinwait method. In the
> +	  spinwait method, all cores randomly jump to Linux. One of the core

	                                                                cores

> +	  gets chosen via lottery and all other keeps spinning on a percpu

	                                  others keep

> +	  variable. This method can not support cpu hotplug and sparse hartid

	                        cannot support CPU hotplug and sparse hartid

> +	  scheme. It should be only enabled for M-mode Linux or platforms relying
> +	  on older firmware without SBI HSM extension. All other platform should

	                                                         platforms

> +	  rely on ordered booing via SBI HSM extension which gets chosen

	                  booting

> +          dynamically at runtime if the firmware supports it.

	  dynamically at runtime if the firmware supports it.

(Last line should be indented with tab + 2 spaces, not 10 spaces.)


-- 
~Randy