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

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Date:	Tue, 28 Jan 2014 13:36:28 -0500
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Yinghai Lu <yinghai@...nel.org>, Kevin Hilman <khilman@...aro.org>,
	Olof Johansson <olof@...om.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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>,
	"Strashko, Grygorii" <grygorii.strashko@...com>
Subject: Re: [PATCH 1/3] memblock, nobootmem: Add memblock_virt_alloc_low()

+ Gryagorii,
On Tuesday 28 January 2014 01:22 PM, Russell King - ARM Linux wrote:
> On Tue, Jan 28, 2014 at 12:23:02PM -0500, Santosh Shilimkar wrote:
>> On Tuesday 28 January 2014 12:12 PM, Yinghai Lu wrote:
>>> Index: linux-2.6/include/linux/bootmem.h
>>> ===================================================================
>>> --- linux-2.6.orig/include/linux/bootmem.h
>>> +++ linux-2.6/include/linux/bootmem.h
>>> @@ -179,6 +179,9 @@ static inline void * __init memblock_vir
>>>                                                     NUMA_NO_NODE);
>>>  }
>>>
>>> +/* Take arch's ARCH_LOW_ADDRESS_LIMIT at first*/
>>> +#include <asm/processor.h>
>>> +
>>>  #ifndef ARCH_LOW_ADDRESS_LIMIT
>>>  #define ARCH_LOW_ADDRESS_LIMIT  0xffffffffUL
>>>  #endif
>>
>> This won't help mostly since the ARM 32 arch don't set ARCH_LOW_ADDRESS_LIMIT.
>> Sorry i couldn't respond to the thread earlier because of travel and
>> don't have access to my board to try out the patches.
> 
> Let's think about this for a moment, shall we...
> 
> What does memblock_alloc_virt*() return?  It returns a virtual address.
> 
> How is that virtual address obtained?  ptr = phys_to_virt(alloc);
> 
> What is the valid address range for passing into phys_to_virt() ?  Only
> lowmem addresses.
> 
> 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.
> 
> So... yes, I think reverting the arch/arm part of this patch is the right
> solution, whether the rest of it should be reverted is something I can't
> comment on.
> 
Grygorri mentioned an alternate to update the memblock_find_in_range_node() so
that it takes into account the limit.

Regards,
Santosh 
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