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From: James Morse <james.morse@arm.com>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: catalin.marinas@arm.com, will.deacon@arm.com,
	dhowells@redhat.com, vgoyal@redhat.com,
	herbert@gondor.apana.org.au, davem@davemloft.net,
	dyoung@redhat.com, bhe@redhat.com, arnd@arndb.de,
	ard.biesheuvel@linaro.org, bhsharma@redhat.com,
	kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 03/11] arm64: kexec_file: invoke the kernel without purgatory
Date: Tue, 1 May 2018 18:46:06 +0100	[thread overview]
Message-ID: <9c830fe8-56d8-b43a-6265-43d31dffe61a@arm.com> (raw)
In-Reply-To: <20180425062629.29404-4-takahiro.akashi@linaro.org>

Hi Akashi,

On 25/04/18 07:26, AKASHI Takahiro wrote:
> On arm64, purugatory would do almosty nothing. So just invoke secondary
> kernel directy by jumping into its entry code.

(Nits: purgatory, almost, directly)


> 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.


> diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S
> index 8021b46c9743..391df91328ac 100644
> --- a/arch/arm64/kernel/cpu-reset.S
> +++ b/arch/arm64/kernel/cpu-reset.S
> @@ -24,9 +24,9 @@
>   *
>   * @el2_switch: Flag to indicate a swich to EL2 is needed.

(Nit: switch)

>   * @entry: Location to jump to for soft reset.
> - * arg0: First argument passed to @entry.
> - * arg1: Second argument passed to @entry.
> - * arg2: Third argument passed to @entry.
> + * arg0: First argument passed to @entry. (relocation list)
> + * arg1: Second argument passed to @entry.(physcal kernel entry)

(Nit: physical)


> + * arg2: Third argument passed to @entry. (physical dtb address)
>   *
>   * Put the CPU into the same state as it would be if it had been reset, and
>   * branch to what would be the reset vector. It must be executed with the
> diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
> index f76ea92dff91..f7dbba00be10 100644
> --- a/arch/arm64/kernel/machine_kexec.c
> +++ b/arch/arm64/kernel/machine_kexec.c
> @@ -205,10 +205,17 @@ 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 case of kexec_file_load syscall, we directly start the kernel,
> +	 * skipping purgatory.

We're not really skipping purgatory, purgatory doesn't exist! For regular kexec
the image/payload we run is up to kexec-tools. For kexec_file_load its a
kernel-image. Purgatory is a kexec-tools-ism.


>  	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->purgatory_info.purgatory_buf ?
> +						0 : kimage->arch.dtb_mem);
> +#else
> +				0);
> +#endif

Where does kimage->arch.dtb_mem come from? This patch won't build until patch 8
adds the config option, which is going to make bisecting any kexec side-effects
tricky.

purgatory_buf seems to only be set in kexec_purgatory_setup_kbuf(), called from
kexec_load_purgatory(), which we don't use. How does this get a value?

Would it be better to always use kimage->arch.dtb_mem, and ensure that is 0 for
regular kexec (as we can't know where the dtb is)? (image_arg may then be a
better name).


Thanks,

James

  reply	other threads:[~2018-05-01 17:49 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25  6:26 [PATCH v9 00/11] arm64: kexec: add kexec_file_load() support AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 01/11] asm-generic: add kexec_file_load system call to unistd.h AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 02/11] kexec_file: make kexec_image_post_load_cleanup_default() global AKASHI Takahiro
2018-04-28  9:45   ` Dave Young
2018-05-01 17:46   ` James Morse
2018-05-07  4:40     ` AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 03/11] arm64: kexec_file: invoke the kernel without purgatory AKASHI Takahiro
2018-05-01 17:46   ` James Morse [this message]
2018-05-07  5:22     ` AKASHI Takahiro
2018-05-11 17:03       ` James Morse
2018-05-15  4:45         ` AKASHI Takahiro
2018-05-15 16:15           ` James Morse
2018-05-18  6:22             ` AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 04/11] arm64: kexec_file: allocate memory walking through memblock list AKASHI Takahiro
2018-05-01 17:46   ` James Morse
2018-05-07  5:59     ` AKASHI Takahiro
2018-05-15  4:35       ` AKASHI Takahiro
2018-05-15 16:17         ` James Morse
2018-05-17  2:10       ` Baoquan He
2018-05-17  2:15         ` Baoquan He
2018-05-17 18:04           ` James Morse
2018-05-18  1:37             ` Baoquan He
2018-05-18  5:07               ` AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 05/11] arm64: kexec_file: load initrd and device-tree AKASHI Takahiro
2018-05-15 16:20   ` James Morse
2018-05-18  7:11     ` AKASHI Takahiro
2018-05-18  7:42       ` AKASHI Takahiro
2018-05-18 15:59         ` James Morse
2018-04-25  6:26 ` [PATCH v9 06/11] arm64: kexec_file: allow for loading Image-format kernel AKASHI Takahiro
2018-05-01 17:46   ` James Morse
2018-05-07  7:21     ` AKASHI Takahiro
2018-05-11 17:07       ` James Morse
2018-05-15  5:13         ` AKASHI Takahiro
2018-05-15 17:14           ` James Morse
2018-05-21  9:32             ` AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 07/11] arm64: kexec_file: add crash dump support AKASHI Takahiro
2018-05-15 17:11   ` James Morse
2018-05-16  8:34     ` James Morse
2018-05-18  9:58       ` AKASHI Takahiro
2018-05-16 10:06     ` James Morse
2018-05-18  9:50       ` AKASHI Takahiro
2018-05-18 10:39     ` AKASHI Takahiro
2018-05-18 16:00       ` James Morse
2018-05-21  9:46         ` AKASHI Takahiro
2018-05-15 17:12   ` James Morse
2018-05-18 15:35     ` Rob Herring
2018-05-21 10:14       ` AKASHI Takahiro
2018-05-24 14:25         ` Rob Herring
2018-04-25  6:26 ` [PATCH v9 08/11] arm64: enable KEXEC_FILE config AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 09/11] include: pe.h: remove message[] from mz header definition AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 10/11] arm64: kexec_file: add kernel signature verification support AKASHI Takahiro
2018-04-25  6:26 ` [PATCH v9 11/11] arm64: kexec_file: add kaslr support AKASHI Takahiro

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