Re: How to efficiently handle DMA and cache on ARMv7 ? (was "Isget_user_pages() enough to prevent pages from being swapped out ?")

[Russell King - ARM Linux]

On Fri, Aug 07, 2009 at 09:58:30AM +0200, Laurent Pinchart wrote:
> Sorry about this, but I'm not sure to understand the speculative prefetching 
> cache issue completely.

The general case with speculative prefetching is that if memory is
accessible, it can be prefetched.

In other words, if we mapped devices without NX (non-exec) set, the
CPU can prefetch instructions from devices, causing random read
accesses.  Yes, I know it sounds crazy, but that's what I'm told
_can_ happen.
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