linux-kernel - Re: mmap hw behavior

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Message-ID: <4A54FFFE.10306@petalogix.com>
Date:	Wed, 08 Jul 2009 22:22:22 +0200
From:	Michal Simek <michal.simek@...alogix.com>
To:	David Miller <davem@...emloft.net>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	mingo@...e.hu, arnd@...db.de, lethal@...ux-sh.org,
	ltp-list@...ts.sourceforge.net
Subject: Re: mmap hw behavior

David Miller wrote:
> From: Michal Simek <michal.simek@...alogix.com>
> Date: Wed, 08 Jul 2009 20:03:27 +0200
>
>   
>> David Miller wrote:
>>     
>>> From: Michal Simek <michal.simek@...alogix.com>
>>> Date: Wed, 08 Jul 2009 19:03:11 +0200
>>>
>>>   
>>>       
>>>> When I call mmap for that open file with pointer to calloc place
>>>> (first parameter, + length zero) it should be one tlb invalidation
>>>> for calloc and new tlb which connect open file.  We check it and we
>>>> don't have any tlb invalidation that's why I think that kernel do
>>>> different thigs.  Or is it there any copying? Or anything different?
>>>>     
>>>>         
>>> There is no need to tlb flush the calloc area unless that memory area
>>> is actually touched by the user application and thus the page is
>>> faulted in.
>>>   
>>>       
>> That calloc area is filled by any value (in that test). Is it mean that
>> for this case when calloc area is touched
>> there must be tlb invalidation + remapping?
>>     
>
> Yes, if the calloc area is written to by the application, there
> should be a tlb flush when the mmap() overrides that virtual region
> with a different mapping.
>   
Can you please point me to any code which exactly do this? (for example
file mm/mmap.c line from ... to ... )

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663

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