Russell King - ARM Linux wrote: > 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. 1. Does the architecture not prevent speculative instruction prefetches from crossing a page boundary? It would be handy under the circumstances. 2. Is NX available on all the CPUs with speculative prefetching behaviour? If it is, just use that for device mappings? -- Jamie -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
