On Mon, Apr 08, 2013 at 03:53:31PM +0100, Andy Whitcroft wrote: > On Sat, Apr 06, 2013 at 04:58:04PM +0200, Andrea Arcangeli wrote: > > > You're right, so this location clearly didn't trigger the problem so I > > didn't notice the noop here. I only exercised the fix in the other > > locations of the file that had the same problem. > > > > It was a noop, so it really couldn't hurt but the below change should > > activate the fix there too. On the same lines, there was a superfluous > > initialization of new_prot too which I cleaned up. > > Although the new code is essentially noop, the other part of the change > in try_preserve_large_page() moves the canon_pgprot() up above the > static_protections() incantation which replaces its value, thus we lose > the effect of that on the protection bits. I suspect this only affects > older CPUs (?) but I do think there is a negative semantic change here: > > + new_prot = canon_pgprot(new_prot); > [...] > new_prot = static_protections(req_prot, address, pfn); > [...] > - new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot)); > + new_pte = pfn_pte(pte_pfn(old_pte), new_prot);
Agreed, canon_pgprot is only for old cpus so it went unnoticed. The patch I posted yesterday will fix that too. static_protections only clear bits. canon_pgprot only clear bits too. So the order won't matter. And unless we want to enforce canon_pgprot to always run after static_protections for whatever reason it should be fine now. If you want to enforce canon_pgprot to always run last let me know. Thanks, Andrea -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
