linux-kernel - Re: [PATCH v9 03/11] arm64: kexec_file: invoke the kernel without purgatory

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Message-ID: <ece8d3cc-127f-6855-52fb-24e4a1d4e823@arm.com>
Date:   Fri, 11 May 2018 18:03:49 +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, 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 v9 03/11] arm64: kexec_file: invoke the kernel without
 purgatory

Hi Akashi,

On 07/05/18 06:22, AKASHI Takahiro wrote:
> On Tue, May 01, 2018 at 06:46:06PM +0100, James Morse wrote:
>> On 25/04/18 07:26, AKASHI Takahiro wrote:
>>> 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)

>>>  	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


>> 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).
> 
> The problem is arch.dtb_mem is currently defined only if CONFIG_KEXEC_FILE.

I thought it was ARCH_HAS_KIMAGE_ARCH, which we can define all the time if
that's what we want.


> So I would like to
> - merge this patch with patch#8
> - change the condition
>         #ifdef CONFIG_KEXEC_FILE
>        				kimage->file_mode ? kimage->arch.dtb_mem : 0);
>         #else
>         			0);
>         #endif

If we can avoid even this #ifdef by always having kimage->arch, I'd prefer that.
If we do that 'dtb_mem' would need some thing that indicates its for kexec_file,
as kexec has a DTB too, we just don't know where it is...


Thanks,

James