Subject: mmap'ed memory cacheable or uncheable

From: "Teresa Tao" <[email-masked]>
Date: Thu, 24 Jul 2003 20:26:59 -0700

Hi there,

I got a question regarding the mmap'ed memory. Is the mmap'ed memory cacheable or uncheable? My driver just use the remap_page_range to map a reserved physical memory.

Thanks in advance!

Teresa

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From: Jun Sun <[email-masked]>
Date: Fri, 25 Jul 2003 15:02:24 -0700

> I got a question regarding the mmap'ed memory. Is the mmap'ed memory cacheable or uncheable? My driver just use the remap_page_range to map a reserved physical memory.

I am pretty much sure it is cached, although I can't pin down exactly
where in the mm subsystem it does so - I have had cache bugs related
to mmap().

Jun

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From: Ralf Baechle <[email-masked]>
Date: Thu, 31 Jul 2003 13:31:21 +0200

On Thu, Jul 24, 2003 at 08:26:59PM -0700, Teresa Tao wrote:

> I got a question regarding the mmap'ed memory. Is the mmap'ed memory
> cacheable or uncheable? My driver just use the remap_page_range to map
> a reserved physical memory.

Mmap(2) creates cachable mappings for everything below the highest memory
address and uncached above that.  That's a somewhat naive mechanism
which fails a few systems but somehow nobody did complain so far ...

  Ralf