linux-kernel - RE: [PATCH] crash dump: don't delete non-E820

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Message-ID: <88DC34334CA3444C85D647DBFA962C270FD7F4B6@SHSMSX102.ccr.corp.intel.com>
Date:	Mon, 5 Nov 2012 01:37:54 +0000
From:	"Zhang, Jun" <jun.zhang@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Fleming, Matt" <matt.fleming@...el.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] crash dump: don't delete non-E820_RAM during init

Hello, Gortmaker
I will modify my subject. Thanks!

Hello, Anvin
from our three options, I think third option is better. But in 3) option, there are two choose, 3.1) is like memmap=REMOVERAM, 3.2) is memmap=CRASHKDUMP.
In 3.1) we maybe need ifdef/endif within the { } of the function (like exactmap).
In 3.2) we can remove the ifdef/endif. 
Which one is the better? Maybe you have a better solution, please share it. 
Thanks!

Next is our three option.
1)  my patch.
2)  modify kexec, only pass two parameters -- memmap=544K@64K 
    memmap=64964K@...68K, in kernel setup_memory_map, we can remove RAM 
    range.
3)  add extra optional, 3.1) like memmap=REMOVERAM
                   3.2) like memmap=CRASHKDUMP

Best Regards!

Jun Zhang
Inet: 8821-4273
Dir.Tel: 86-21-6116-4273
Email: jun.zhang@...el.com

-----Original Message-----
From: H. Peter Anvin [mailto:hpa@...or.com] 
Sent: Saturday, November 03, 2012 12:38 AM
To: Zhang, Jun
Cc: Thomas Gleixner; Ingo Molnar; x86@...nel.org; Andrew Morton; Fleming, Matt; Paul Gortmaker; linux-kernel@...r.kernel.org
Subject: Re: [PATCH] To crash dump, we need keep other memory type except E820_RAM, because other type come from BIOS or firmware is used by other code(for example: PCI_MMCONFIG).

On 11/01/2012 01:49 AM, Zhang, Jun wrote:
> Hello, Anvin
> 
> Thank for your advice.
> 
> Hello, All
> 
> the next patch is made by 2), please review it. Thanks!
> 

No, it is not.

You are still modifying the behavior of the kernel depending on CONFIG_CRASH_DUMP.

CONFIG_CRASH_DUMP doesn't mean "we are doing a crash dump".  It means "it is possible to use this kernel to do a crash dump".

Either you are using standard kernel parameters in a standard way which is what option 2 was supposed to be -- it should require no kernel changes! -- or you have to put something in a code path specific to a crash dump.

	-hpa