linux-kernel - Re: [PATCH] mm: fix boundary checking in free_bootmem

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Date:	Fri, 14 Mar 2008 09:44:50 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	"Andi Kleen" <ak@...e.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>, mingo@...e.hu,
	clameter@....com, linux-kernel@...r.kernel.org,
	"Yasunori Goto" <y-goto@...fujitsu.com>,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] mm: fix boundary checking in free_bootmem_core

On 14 Mar 2008 12:58:44 +0100, Andi Kleen <andi@...stfloor.org> wrote:
> "Yinghai Lu" <yhlu.kernel@...il.com> writes:
>  >
>  > then i tried to reserve 64M or 128M RAM before that, and free that
>  > before gart/switotble try to allloc_bootmem under 4g.
>
>  Sounds like an incredible hack. There are far better ways to do that
>  for bootmem allocations. e.g. you can just specify a high enough "goal"
>  That is how swiotlb solves a similar problem (at least before my
>  mask allocator rewrite)

I don't think so.

anyway, otherway to workaround it is
change
                return __earlyonly_bootmem_alloc(node, size, size,
                                __pa(MAX_DMA_ADDRESS));
in vmemmap_alloc_block to
                return __earlyonly_bootmem_alloc(node, size, size,
                                __pa(MAX_DMA_ADDRESS + (1<<27)));
to make room for gart. but that is global change. and may affect other
platform. and don't make sure gart will get it.

also i assume swiotlb need that range is less than 4g.

>
>
>  > >  with your improved free_bootmem()
>  >
>  > using phys_to_nid()? it seems we only have that on x86_64.
>
>  pfn/page_to_nid() is generic afaik.

still in bootmem stage? page->flags is ready at that time?

YH
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