linux-kernel - Re: [PATCH 1/3] memblock, nobootmem: Add memblock_virt_alloc

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Date:	Tue, 28 Jan 2014 12:17:37 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Santosh Shilimkar <santosh.shilimkar@...com>,
	Yinghai Lu <yinghai@...nel.org>,
	Kevin Hilman <khilman@...aro.org>,
	Olof Johansson <olof@...om.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Dave Hansen <dave.hansen@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH 1/3] memblock, nobootmem: Add memblock_virt_alloc_low()

On Tue, Jan 28, 2014 at 10:22 AM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
>
> Hence, having ARCH_LOW_ADDRESS_LIMIT set to 4GB-1 by default seems to be
> completely rediculous - and presumably this also fails on x86_32 if it
> returns memory up at 4GB.

Agreed. That looks broken even on x86-32. The low address limit is not
even *close* to 4GB in general on 32-bit, since you not only have the
TASK_SIZE, you have the kmap and the vmalloc area. On x86-32,
ARCH_LOW_ADDRESS_LIMIT should be MAXMEM, which iirc is somewhere
around 890MB or so. Not 4G.

                    Linus
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