linux-kernel - Re: [PATCH 0/4] memblock related fixes for -tip

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Date:	Wed, 13 Oct 2010 16:14:43 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH 0/4] memblock related fixes for -tip

 On 10/13/2010 03:06 PM, Yinghai Lu wrote:
> On 10/13/2010 01:03 PM, Jeremy Fitzhardinge wrote:
>>> a) Add an explicit interface to allocate bottoms-up, and have Xen use it
>>> because it needs it.  This is appropriate if (and only if) the
>>> allocations in Xen aren't underneath a bunch of extra layers.
>> The allocation is done in find_early_table_space() in x86/mm/init.c, so
>> the allocation call itself can't be easily replaced, but I suppose some
>> of the parameters could be global and tweaked by Xen code, but that's
>> pretty ugly.
> we already have
>         base = memblock_find_in_range(start, max_pfn_mapped<<PAGE_SHIFT,
>                                         tables, PAGE_SIZE);
>
> so looks like xen have set max_pfn_mapped wrong?

The Xen code is setting the max_pfn_mapped correctly, but it is just
being overridden by:

	max_pfn_mapped = KERNEL_IMAGE_SIZE >> PAGE_SHIFT;

in setup_arch() - and KERNEL_IMAGE_SIZE is hard-coded to 512MB...

How is this correct?  Does kernel/head_64.S map everything up to 512MB
or something?

    J
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