linux-kernel - 答复: [PATCH] Initialize max_pfn_mapped as initial ident mapping size for x86

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Message-ID: <d493264b-7da0-41bd-b0bc-219b1a180f10@default>
Date:	Sun, 4 Mar 2012 23:49:31 -0800 (PST)
From:	Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:	<stable@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Cc:	<mingo@...hat.com>, <konrad.wilk@...cle.com>, <yinghai@...nel.org>,
	<tglx@...utronix.de>, <joe.jin@...cle.com>, <hpa@...or.com>
Subject: 答复: [PATCH] Initialize max_pfn_mapped as initial ident mapping size for x86_64


----- zhenzhong.duan@...cle.com 写道：

> It's better to initialize max_pfn_mapped as initial ident
> mapping size but not initial kernel map size for x86_64.
> This is also in accordance with i386 code.
> 
> It lead to page tables allocation to as high as 1G for
> init_memory_mapping,
> this will allow larger crashkernel reservation.
> 
> Tested on HP DL980G7, it can reserve more than 521MiB space for kdump
> kernel now.
> http://bugzilla.oracle.com/bugzilla/show_bug.cgi?id=13405
> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Yinghai Lu <yinghai@...nel.org>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
> Tested-by: Dawei Pang <dawei.pang@...com>
> ---
>  arch/x86/kernel/head64.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 3a3b779..3beb94f 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -77,7 +77,7 @@ void __init x86_64_start_kernel(char *
> real_mode_data)
>  	/* Make NULL pointers segfault */
>  	zap_identity_mappings();
>  
> -	max_pfn_mapped = KERNEL_IMAGE_SIZE >> PAGE_SHIFT;
> +	max_pfn_mapped = PUD_PAGE_SIZE >> PAGE_SHIFT;
>  
>  	for (i = 0; i < NUM_EXCEPTION_VECTORS; i++) {
>  #ifdef CONFIG_EARLY_PRINTK
> -- 
> 1.7.3

Hmm, any comment is welcome
thanks

zduan
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