Message-ID: <4142161F.1060904@nortelnetworks.com>
Date: Fri, 10 Sep 2004 15:01:19 -0600
From: Chris Friesen <cfriesen@nortelnetworks.com>
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To: Linux kernel <linux-kernel@vger.kernel.org>
CC: Hugh Dickins <hugh@veritas.com>
Subject: problems with remap_page_range() and virt_to_phys() -- solved
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Friesen, Christopher [CAR:VC21:EXCH] wrote:


> The problem that I'm having is that after the call to remap_page_range, 
> the result of
> 
> virt_to_phys(map_addr)
> 
> is not equal to "phys", and I assume it should be since its supposed to 
> be pointing to the same physical page as "virt".

I seem to have found my problem.  There were two things involved:

1) virt_to_phys() doesn't work on user addresses, so you basically have to walk 
the page tables.  For ppc, iopa() seems to do this although there is a comment 
about it not working on pmac (which it seems to).

2) to setup the vma for unmapped areas I was using mmap with MAP_PRIVATE.  On 
the first write by userspace, the mapping was changed and the user page was no 
longer mapped to the desired kernel page.  Changing this to MAP_SHARED fixed it.

Chris
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