linux-kernel - Re: [PATCH] x86: put initial_pg

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Message-ID: <49AACAA3.1060806@kernel.org>
Date:	Sun, 01 Mar 2009 09:49:23 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: [PATCH] x86: put initial_pg_tables into bss -v2

H. Peter Anvin wrote:
> Yinghai Lu wrote:
>> Impact: cleanup
>>
>> Don't use ram after _end blindly for pagetables.
>> put those pg table into bss
>>
>> also remove init_pg_tables_start/end tricks all around
>>
>> v2: keep initial page table up to 512M only.
>>
> 
> I really, REALLY, don't like this.  This is going right back to the
> situation which we had before the dynamically generated page tables.  We
> now have yet another hardcoded limit, and big chunk of wasted memory in
> case we don't need to allocate it all.

that limit is there in for 64 too. aka 512M direct mapping. (need 1Mbytes space for page tables)

we can get rid of that limit: with careful link sequence to make sure that code init_memory_mapping and before is some fixed range.

YH
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