linux-kernel - Re: [PATCH] WIP: HACK: LPAE, BOOTMEM and NO

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Date:	Thu, 25 Jul 2013 18:33:14 -0400
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Tejun Heo <tj@...nel.org>
CC:	Yinghai Lu <yinghai@...nel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	"sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
	Sam Ravnborg <sam@...nborg.org>, <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] WIP: HACK: LPAE, BOOTMEM and NO_BOOTMEM

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@....linux.org.uk> 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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