From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933428Ab3B0BDZ (ORCPT ); Tue, 26 Feb 2013 20:03:25 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:24632 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760226Ab3BZX5s convert rfc822-to-8bit (ORCPT ); Tue, 26 Feb 2013 18:57:48 -0500 MIME-Version: 1.0 Message-ID: <91983d94-7b7d-4a0b-9470-e7cd823ba139@default> Date: Tue, 26 Feb 2013 15:57:35 -0800 (PST) From: Boris Ostrovsky To: Cc: , , , , Subject: Re: [PATCH] mm/x86: Flush lazy MMU when DEBUG_PAGEALLOC is set X-Mailer: Zimbra on Oracle Beehive Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Content-Disposition: inline X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- hpa@zytor.com wrote: > On 02/26/2013 02:56 PM, Boris Ostrovsky wrote: > > When CONFIG_DEBUG_PAGEALLOC is set page table updates made by > > kernel_map_pages() are not made visible (via TLB flush) immediately > if lazy > > MMU is on. In environments that support lazy MMU (e.g. Xen) this may > lead to > > fatal page faults, for example, when zap_pte_range() needs to > allocate pages > > in __tlb_remove_page() -> tlb_next_batch(). > > > > Signed-off-by: Boris Ostrovsky > > --- > > arch/x86/mm/pageattr.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c > > index ca1f1c2..7b3216e 100644 > > --- a/arch/x86/mm/pageattr.c > > +++ b/arch/x86/mm/pageattr.c > > @@ -1369,6 +1369,8 @@ void kernel_map_pages(struct page *page, int > numpages, int enable) > > * but that can deadlock->flush only current cpu: > > */ > > __flush_tlb_all(); > > + > > + arch_flush_lazy_mmu_mode(); > > } > > > > #ifdef CONFIG_HIBERNATION > > > > This sounds like a critical fix, i.e. a -stable candidate. Am I > correct? I considered copying stable but then I decided that this is a debugging feature --- kernel_map_pages() is only defined if CONFIG_DEBUG_PAGEALLOC is set and my thinking was that stable kernels usually don't do this. -boris