linux-kernel - get_user_pages() cache issues on ARM

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Date:	Sat, 30 Sep 2006 18:59:50 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	rmk@....linux.org.uk
CC:	dhylands@...il.com, guinan@...ebutton.com,
	linux-kernel@...r.kernel.org
Subject: get_user_pages() cache issues on ARM

Hi Russell,

The get_user_pages() vs dcache coherency issue still seems to be
unresolved on ARM.

See flush_anon_page() and flush_kernel_dcache_page() in
Documentation/cachetlb.txt and their implementation on PARISC.

Can you please take a look at this?

Thanks,
Miklos

------- Start of forwarded message -------
Date: Sun, 24 Sep 2006 20:20:15 -0700
From: "Dave Hylands" <dhylands@...il.com>
To: "Miklos Szeredi" <miklos@...redi.hu>
Subject: Re: [fuse-devel] ARM cross build issues
Cc: guinan@...ebutton.com, fuse-devel@...ts.sourceforge.net
In-Reply-To: <E1GR461-0003WJ-00@...ka.pomaz.szeredi.hu>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

Hi Miklos,

Sending this to the list...

> > 2.6.18 still calls get_user_pages will the NULL vma. I verified that
> > the flush_cache_all patch made things work for me under 2.6.11
> > (big-endian ARM) and 2.6.17 (little-endian ARM).
>
> get_user_pages() should do the right thing on it's own.  So passing
> NULL vma is the normal thing to do, and the workaround should not be
> needed.
>
> So if 2.6.18 works without the patch, then it's fixed, otherwise not.

So 2.6.18 does NOT work on the ARM using the fuse.ko that gets built from the
kernel sources.

If I add the flush_cache_all() patch or the DCAHCE_BUG patch, then
everything works fine.

This was tested on my gumstix, which is an ARM XScale PXA255 running
in little-endian mode, using 2.6.18. I was using the hello filesystem
for the tests.

- -- 
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/
------- End of forwarded message -------
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