linux-kernel - Re: [v2 1/5] arm64: kdump: reserve memory for crash dump kernel

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Message-ID: <20150428091935.GJ15033@dhcp-16-116.nay.redhat.com>
Date:	Tue, 28 Apr 2015 17:19:35 +0800
From:	Baoquan He <bhe@...hat.com>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:	catalin.marinas@....com, will.deacon@....com, vgoyal@...hat.com,
	hbabus@...ibm.com, geoff@...radead.org, broonie@...nel.org,
	david.griego@...aro.org, kexec@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [v2 1/5] arm64: kdump: reserve memory for crash dump kernel

> +#ifdef CONFIG_CRASH_DUMP
> +/*
> + * reserve_elfcorehdr() - reserves memory for elf core header
> + *
> + * This function reserves memory area given in "elfcorehdr=" kernel command
> + * line parameter. The memory reserved is used by a dump capture kernel to
> + * identify the memory used by primary kernel.
> + */

Hi AKASHI,

May I know why elfcorehdr need be reserved separately but not locate a
memory region in crashkernel reserved region like all other ARCHs? Is
there any special reason?

Thanks
Baoquan

> +static void __init reserve_elfcorehdr(void)
> +{
> +	if (!elfcorehdr_size)
> +		return;
> +
> +	if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
> +		pr_warn("elfcorehdr reservation failed - memory is in use (0x%llx)\n",
> +			elfcorehdr_addr);
> +		return;
> +	}
> +
> +	if (memblock_reserve(elfcorehdr_addr, elfcorehdr_size)) {
> +		pr_warn("elfcorehdr reservation failed - out of memory\n");
> +		return;
> +	}
> +
> +	pr_info("Reserving %lldKB of memory at %lldMB for elfcorehdr\n",
> +		elfcorehdr_size >> 10, elfcorehdr_addr >> 20);
> +}
> +#endif /* CONFIG_CRASH_DUMP */
>  /*
>   * Return the maximum physical address for ZONE_DMA (DMA_BIT_MASK(32)). It
>   * currently assumes that for memory starting above 4G, 32-bit devices will
> @@ -170,6 +247,13 @@ void __init arm64_memblock_init(void)
>  		memblock_reserve(__virt_to_phys(initrd_start), initrd_end - initrd_start);
>  #endif
>  
> +#ifdef CONFIG_KEXEC
> +	reserve_crashkernel(memory_limit);
> +#endif
> +#ifdef CONFIG_CRASH_DUMP
> +	reserve_elfcorehdr();
> +#endif
> +
>  	early_init_fdt_scan_reserved_mem();
>  
>  	/* 4GB maximum for 32-bit only capable devices */
> -- 
> 1.7.9.5
> 
> --
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