linux-kernel - Re: [PATCH] x86: crash kernel reserve with reserve

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Message-ID: <m18wdypvjd.fsf@fess.ebiederm.org>
Date:	Sun, 22 Nov 2009 04:56:54 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vivek Goyal <vgoyal@...hat.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	kexec@...ts.infradead.org
Subject: Re: [PATCH] x86: crash kernel reserve with reserve_early

Yinghai Lu <yhlu.kernel@...il.com> writes:

> [PATCH] x86: crash kernel reserve with reserve_early
>
> use find_e820_area/reserve_early instead.
> will get next good one automatically with alignment

Semantically this is broken, as you are now ignoring a passed in
base address if one is supplied.  What problem are you trying to fix?

Eric

>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> ---
>  arch/x86/kernel/setup.c |   60 ++++++++++--------------------------------------
>  1 file changed, 13 insertions(+), 47 deletions(-)
>
> Index: linux-2.6/arch/x86/kernel/setup.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/setup.c
> +++ linux-2.6/arch/x86/kernel/setup.c
> @@ -488,42 +488,11 @@ static void __init reserve_early_setup_d
>  
>  #ifdef CONFIG_KEXEC
>  
> -/**
> - * Reserve @size bytes of crashkernel memory at any suitable offset.
> - *
> - * @size: Size of the crashkernel memory to reserve.
> - * Returns the base address on success, and -1ULL on failure.
> - */
> -static
> -unsigned long long __init find_and_reserve_crashkernel(unsigned long long size)
> -{
> -	const unsigned long long alignment = 16<<20; 	/* 16M */
> -	unsigned long long start = 0LL;
> -
> -	while (1) {
> -		int ret;
> -
> -		start = find_e820_area(start, ULONG_MAX, size, alignment);
> -		if (start == -1ULL)
> -			return start;
> -
> -		/* try to reserve it */
> -		ret = reserve_bootmem_generic(start, size, BOOTMEM_EXCLUSIVE);
> -		if (ret >= 0)
> -			return start;
> -
> -		start += alignment;
> -	}
> -}
> -
>  static inline unsigned long long get_total_mem(void)
>  {
>  	unsigned long long total;
>  
> -	total = max_low_pfn - min_low_pfn;
> -#ifdef CONFIG_HIGHMEM
> -	total += highend_pfn - highstart_pfn;
> -#endif
> +	total = max_pfn - min_low_pfn;
>  
>  	return total << PAGE_SHIFT;
>  }
> @@ -532,6 +501,8 @@ static void __init reserve_crashkernel(v
>  {
>  	unsigned long long total_mem;
>  	unsigned long long crash_size, crash_base;
> +	const unsigned long long alignment = 16<<20;	/* 16M */
> +	unsigned long long start;
>  	int ret;
>  
>  	total_mem = get_total_mem();
> @@ -543,21 +514,16 @@ static void __init reserve_crashkernel(v
>  
>  	/* 0 means: find the address automatically */
>  	if (crash_base <= 0) {
> -		crash_base = find_and_reserve_crashkernel(crash_size);
> -		if (crash_base == -1ULL) {
> -			pr_info("crashkernel reservation failed. "
> -				"No suitable area found.\n");
> -			return;
> -		}
> +		start = alignment;
>  	} else {
> -		ret = reserve_bootmem_generic(crash_base, crash_size,
> -					BOOTMEM_EXCLUSIVE);
> -		if (ret < 0) {
> -			pr_info("crashkernel reservation failed - "
> -				"memory is in use\n");
> -			return;
> -		}
> +		start = crash_base;
> +	}
> +	crash_base = find_e820_area(start, ULONG_MAX, crash_size, alignment);
> +	if (crash_base == -1ULL) {
> +		pr_info("crashkernel reservation failed - No suitable area found.\n");
> +		return;
>  	}
> +	reserve_early(crash_base, crash_base + crash_size, "CRASH KERNEL");
>  
>  	printk(KERN_INFO "Reserving %ldMB of memory at %ldMB "
>  			"for crashkernel (System RAM: %ldMB)\n",
> @@ -935,6 +901,8 @@ void __init setup_arch(char **cmdline_p)
>  
>  	reserve_initrd();
>  
> +	reserve_crashkernel();
> +
>  	vsmp_init();
>  
>  	io_delay_init();
> @@ -965,8 +933,6 @@ void __init setup_arch(char **cmdline_p)
>  
>  	initmem_init(0, max_pfn, acpi, k8);
>  
> -	reserve_crashkernel();
> -
>  #ifdef CONFIG_X86_64
>  	/*
>  	 * dma32_reserve_bootmem() allocates bootmem which may conflict
--
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