linux-kernel - Re: [PATCH 28/31] memblock: Export MEMBLOCK

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Date:	Wed, 28 Jul 2010 16:29:52 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 28/31] memblock: Export MEMBLOCK_ERROR again

On Tue, 2010-07-27 at 22:53 -0700, H. Peter Anvin wrote:
> On 07/27/2010 10:19 PM, Benjamin Herrenschmidt wrote:
> > 
> > Screw it, I don't like it but I'll just split your patch in two for now
> > and keep 0. It's a bit fishy but memblock does mostly top-down
> > allocations and so shouldn't hit 0, and in practice the region at 0 is,
> > I beleive, reserved, but we need to be extra careful and might need to
> > revisit that a bit.
> > 
> > That's an area where I don't completely agree with Linus, ie, 0 is a
> > perfectly valid physical address for memblock to return :-)
> > 
> 
> On x86, physical address 0 contains the real-mode IVT and will thus be
> reserved, at least for the forseeable future.  Other architectures may
> very well have non-special RAM there.

Right, that's my point. Anyways, I'm making 0 special for now and adding
a wart to prevent the allocator from returning something below
PAGE_SIZE. If we want to revisit that later we can.

Cheers,
Ben.


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