Re: [PATCH] WIP: HACK: LPAE, BOOTMEM and NO_BOOTMEM

[Santosh Shilimkar]

Tejun,

On Monday 01 July 2013 10:10 AM, Santosh Shilimkar wrote:
> On Saturday 29 June 2013 04:08 PM, Yinghai Lu wrote:
>> On Sat, Jun 29, 2013 at 12:55 PM, Russell King - ARM Linux
>> <linux@xxxxxxxxxxxxxxxx> wrote:
>>> On Sat, Jun 29, 2013 at 12:29:55PM -0700, Yinghai Lu wrote:
>>>>>> On these SoCs which Santosh is working on, the main physical memory
>>>>>> mapping is above 4GB, with just a small alias below 4GB to allow the
>>>>>> system to boot without the MMU being on, as they may have more than
>>>>>> 4GB of RAM.  As I understand it, the small alias below 4GB is not
>>>>>> suitable for use as a "lowmem" mapping.
>>>>
>>>> is that 32bit ARM or 64bit ARM?
>>>
>>> Only 32-bit has LPAE.  Such things don't make sense on 64-bit CPUs.
>>
> Thanks Russell for clarifying the issue on the thread. Another major
> reason of not being to use 32 bit alias address space for lowmem
> is that address space isn't coherent on the SOC am dealing with.
> 
>> 32bit ARM does not support NO_BOOTMEM yet.
>>
>> arch/arc/Kconfig:       select NO_BOOTMEM
>> arch/arm64/Kconfig:     select NO_BOOTMEM
>> arch/sparc/Kconfig:     select NO_BOOTMEM
>> arch/x86/Kconfig:config NO_BOOTMEM
>>
>>
>> so may need to
>> 1. make 32bit ARM to use NO_BOOTMEM at first.
>>
> Sorry. I should have mentioned that in the change-log. 
> I have been carrying some WIP patches for ARM. Will post them
> on ARM list after finishing remainder of the testing.
> 
>> 2 .we can add alloc_memblock as MACRO or inline for bootmem arches,
>>
>> 3. NO_BOOTMEM arches will have alloc_memblock in nobootmem.c
>>
>> 4. replace alloc_bootmem calling with alloc_memblock calling in core code.
>>
> Great that we all agree to see back of nobootmem.c and have a direct
> memblock API. Will be happy to help in conversion to proposed new interfaces
> if I can get the alloc_memblock API and core related changes.
> 
> Will be good to know who is going to create proposed memblock API
> so that we all can collaborate in conversion.
> 
Any comments here. I would like to know your plan for the new
API. You might have seen on the ARM no-bootmem thread, we started to
move ARM to nobootmem with Russell's help.

Regards,
Santosh

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