On Thu, Apr 26, 2007 at 05:53:49PM +1000, Nick Piggin wrote: > I had a couple of questions which I'm hoping someone would be kind > enough to explain :) ... > I wonder how this is different to all the other code which calls > lazy_mmu_prot_update() after set_pte_at(). do_swap_page, for example, > _could_ fault in executable code, couldn't it? The do_swap_page code does look suspect. It seems to be working on ia64 because a DMA transfer of data from swap to the allocated page is removing old lines from the icache. If code on an anonymous page was swapping in without direct DMA to the page then the same problem could occur. I can't think of a reasonable situation that would cause swapping in to not use DMA. Swapping to/from NFS does not seem reasonable to me anyway. > It is because do_swap_page uses flush_icache_page()? So why doesn't > the flush_icache_page() work in do_no_page as well? (It seems to look > like a superset of lazy_mmu_prot_update on ia64?!?). flush_icache_page() on ia64 is provided by include/asm-ia64/cacheflush.h. It doesn't have any effect at all. #define flush_icache_page(vma,page) do { } while (0) lazy_mmu_prot_update() is supposed to get icache flushes done when they need to be. And it is supposed to avoid unneeded flushes when the icache is known to be clean for a page. -- Mike Stroyan, mike.stroyan@xxxxxx - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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