how can I cleanly exclude memory from the kernel memory allocator?

Colin Cross ccross at
Wed Apr 20 02:48:52 EDT 2011

On Tue, Apr 19, 2011 at 4:33 PM, Larry Bassel <lbassel at> wrote:
> On 25 Mar 11 20:27, Russell King - ARM Linux wrote:
>> On Fri, Mar 25, 2011 at 10:39:28AM -0700, Larry Bassel wrote:
>> > OK, please ignore my previous mail, I see that .fixup can be
>> > used to adjust tags. It appears to me, however, that using a
>> > .reserve function calling memblock_reserve will be an
>> > easier way of doing what I need.
>> Absolutely.
> Hopefully I'm just missing something obvious, but
> when I call memblock_reserve (in .38) to reserve a block
> of memory away from the general kernel memory pool,
> I find that an ioremap of memory within the reserved block
> still fails because pte_valid() is apparently true.
> Is this intended behavior? If so, what would the
> correct way of separating memory from the system be
> so that there is no longer a 1-to-1 1M mapping for
> this memory and ioremap (creating the *only* mapping
> for this memory) is allowed?

You need to call memblock_remove, not memblock_reserve.

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