linux-kernel - 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

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Message-ID: <5090AB3C.5050405@zytor.com>
Date:	Tue, 30 Oct 2012 21:38:20 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Zhang, Jun" <jun.zhang@...el.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] 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 10/30/2012 08:39 PM, Zhang, Jun wrote:
> Hello, Anvin
> Thanks!
>
> Hello, all
> Next is my the latest version, please review it.
> Thanks!

You're still starting in the wrong end which is confusing for the reader.

What you probably want to say is something more like:

"We are doing a crash dump, so remove all RAM ranges as they are the 
ones that need to be dumped.  We still need all non-RAM information in 
order to do I/O."

At that point it should be pretty obvious that the patch is wrong.  What 
if we are *not* doing a crash dump?  Just because crash dump is compiled 
in doesn't mean that that is what we are doing right now.

	-hpa

>  From 141546c77ff7be523a9e72f5259df4a6827f2c1a Mon Sep 17 00:00:00 2001
> From: jzha144 <jun.zhang@...el.com>
> Date: Wed, 31 Oct 2012 08:51:18 +0800
> Subject: [PATCH] If we are doing a crash dump, we still need non-E820_RAM
>   memory type address information, which come from BIOS or
>   firmware. for example: PCI_MMCONFIG check this address.
>
> Signed-off-by: jzha144 <jun.zhang@...el.com>
> ---
>   arch/x86/kernel/e820.c |    9 +++++++++
>   1 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index df06ade..f8672d0 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -851,6 +851,15 @@ static int __init parse_memmap_opt(char *p)
>   		 * reset.
>   		 */
>   		saved_max_pfn = e820_end_of_ram_pfn();
> +
> +		/*
> +		 * If we are doing a crash dump, we still need non-E820_RAM
> +		 * memory type address information. so we only remove
> +		 * E820_RAM type.
> +		 */
> +		e820_remove_range(0, ULLONG_MAX, E820_RAM, 1);
> +		userdef = 1;
> +		return 0;
>   #endif
>   		e820.nr_map = 0;
>   		userdef = 1;
>


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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