linux-kernel - Re: [PATCH v12 13/16] arm64: kexec_file: invoke the kernel without purgatory

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Date:   Thu, 26 Jul 2018 14:36:07 +0100
From:   James Morse <james.morse@....com>
To:     AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:     catalin.marinas@....com, will.deacon@....com, dhowells@...hat.com,
        vgoyal@...hat.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, dyoung@...hat.com, bhe@...hat.com,
        arnd@...db.de, schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        ard.biesheuvel@...aro.org, bhsharma@...hat.com,
        kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 13/16] arm64: kexec_file: invoke the kernel without
 purgatory

Hi Akashi,

On 24/07/18 07:57, AKASHI Takahiro wrote:
> On arm64, purgatory would do almost nothing. So just invoke secondary
> kernel directly by jumping into its entry code.
> 
> While, in this case, cpu_soft_restart() must be called with dtb address
> in the fifth argument, the behavior still stays compatible with kexec_load
> case as long as the argument is null.

This patch conflicts with commit 76f4e2da45b4 ("arm64: kexec: always reset to
EL2 if present") in the arm64 tree.

Thanks,

James

> diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
> index f76ea92dff91..830a5063e09d 100644
> --- a/arch/arm64/kernel/machine_kexec.c
> +++ b/arch/arm64/kernel/machine_kexec.c
> @@ -205,10 +205,18 @@ void machine_kexec(struct kimage *kimage)
>  	 * uses physical addressing to relocate the new image to its final
>  	 * position and transfers control to the image entry point when the
>  	 * relocation is complete.
> +	 * In kexec case, kimage->start points to purgatory assuming that
> +	 * kernel entry and dtb address are embedded in purgatory by
> +	 * userspace (kexec-tools).
> +	 * In kexec_file case, the kernel starts directly without purgatory.
>  	 */
> -
>  	cpu_soft_restart(kimage != kexec_crash_image,
> -		reboot_code_buffer_phys, kimage->head, kimage->start, 0);
> +		reboot_code_buffer_phys, kimage->head, kimage->start,
> +#ifdef CONFIG_KEXEC_FILE
> +						kimage->arch.dtb_mem);
> +#else
> +						0);
> +#endif
>  
>  	BUG(); /* Should never get here. */
>  }