linux-kernel - Re: [PATCH] x86: only put e820 ram entries in resource tree

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Message-ID: <20080825141901.GE18914@redhat.com>
Date:	Mon, 25 Aug 2008 10:19:01 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Bernhard Walle <bwalle@...e.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] x86: only put e820 ram entries in resource tree

On Sun, Aug 24, 2008 at 03:44:57PM -0700, Yinghai Lu wrote:
> may need user to have new kexec tools that could create e820 table
> from /sys/firmware/memmap instead of /proc/iomem for second kernel
> 
> Signed-off-by: Yinghai Lu <yhlu.kernel@...il.com>
> Cc: Bernhard Walle <bwalle@...e.de>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> 
> Index: linux-2.6/arch/x86/kernel/e820.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/e820.c
> +++ linux-2.6/arch/x86/kernel/e820.c
> @@ -1279,6 +1279,10 @@ void __init e820_reserve_resources(void)
>  
>  	res = alloc_bootmem_low(sizeof(struct resource) * e820.nr_map);
>  	for (i = 0; i < e820.nr_map; i++) {
> +		if (e820.map[i].type != E820_RAM) {
> +			res++;
> +			continue;
> +		}
>  		end = e820.map[i].addr + e820.map[i].size - 1;
>  #ifndef CONFIG_RESOURCES_64BIT
>  		if (end > 0x100000000ULL) {

I think this will wipe out ACPI related entries also from /proc/iomem
and kdump will be broken as second kernel needs to know about the ACPI
areas.

Though, if all these entries are available in /sys/firmware/memap then
probably one can modify kexec-tools to grep RAM entries from /proc/iomem and
rest of the entries from /sys/firmware/memmap.

I would not prefer doing that it makes the logic twisted.

Thanks
Vivek
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