Re: [PATCH 1/3] memblock, nobootmem: Add memblock_virt_alloc_low()

From: Linus Torvalds
Date: Tue Jan 28 2014 - 15:17:49 EST


On Tue, Jan 28, 2014 at 10:22 AM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> 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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