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List:       linux-arm-kernel
Subject:    Re: coherent DMA memory on ARMv6
From:       Lennert Buytenhek <buytenh () wantstofly ! org>
Date:       2007-05-31 19:28:22
Message-ID: 20070531192822.GZ26191 () xi ! wantstofly ! org
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On Tue, Apr 10, 2007 at 12:22:40PM +0100, Catalin Marinas wrote:

> >> Overlapping section/supersection TLB entries are already considered
> >> unpredictable by the ARM ARM and Linux breaks this rule when booting.
> >
> > I suspect that's not the only time - consider the following case.
> >
> > Current page tables have section mappings at virtual address 0xe0000000.
> > Next page tables have supersection mappings at that virtual address.
> > We do a MM switch between the two page tables.
> 
> Aren't the global mapping meant to be the same for all the tasks? The
> user mappings use pages only anyway, so no problem with overlapping.

Things like vmalloc() (and ioremap()) cause the global mappings not to
be the same for all tasks, although for the ioremap() case there is an
explicit check.

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