From: James Bottomley <[EMAIL PROTECTED]> Date: Sun, 19 Mar 2006 14:53:08 -0600
> Actually, this is my specific worry. On parisc, the coherence index > associated with the DMA is that of the kernel mapping, not the user > mappings, so DMA only flushes the kernel cache for the line, not the > user one. If nothing happens to purge the user line, DMA to anon pages > won't work on parisc either. You have physically indexed caches, thus cache coherency transactions should purge all cache lines with that same physical TAG. If not, you have much larger problems. > I do think we need to begin considering it. The user space device > managers, like hal, are starting to use SG_IO to interrogate devices, > making it much more prevalent than before. It's got to be only a matter > of time before this issue bites something like hal. > > Is the principle that get_user_pages() should return coherent pages OK? > If so, I think the fix is to have get_user_pages do a specific user page > flush for anonymous pages. Direct I/O is another problematic case. - To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
