From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965146Ab1GMJMr (ORCPT ); Wed, 13 Jul 2011 05:12:47 -0400 Received: from smtp.eu.citrix.com ([62.200.22.115]:32232 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965124Ab1GMJMq (ORCPT ); Wed, 13 Jul 2011 05:12:46 -0400 X-IronPort-AV: E=Sophos;i="4.65,524,1304294400"; d="scan'208";a="6757848" Subject: Re: [Xen-devel] [PATCH] xen: update machine_to_phys_order on resume From: Ian Campbell To: Konrad Rzeszutek Wilk , Keir Fraser , Jan Beulich CC: Olaf Hering , "linux-kernel@vger.kernel.org" , "xen-devel@lists.xensource.com" In-Reply-To: <20110712181118.GA18662@dumpdata.com> References: <20110701104148.GA32729@aepfle.de> <20110712164342.GA12867@aepfle.de> <20110712181118.GA18662@dumpdata.com> Content-Type: text/plain; charset="UTF-8" Organization: Citrix Systems, Inc. Date: Wed, 13 Jul 2011 10:12:44 +0100 Message-ID: <1310548364.634.355.camel@zakaz.uk.xensource.com> MIME-Version: 1.0 X-Mailer: Evolution 2.32.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-07-12 at 19:11 +0100, Konrad Rzeszutek Wilk wrote: > On Tue, Jul 12, 2011 at 06:43:42PM +0200, Olaf Hering wrote: > > > > Migration of pv guests fails, the guest crashes on the target host once the > > guest is unpaused after transit. It happens when the guest is started on a > > small systen, then migrated from that small system to a large system. > > If the guest is started on a large system, then migrated to a small system and > > back to the large system, the migration will be successful. > > > > The issue is that mfn_to_pfn() makes use of machine_to_phys_order, which > > is only configured once early in the boot process. After migration to a > > large host the mfns will exceed the order from the small system and a > > wrong code path is taken. > > > > Calling xen_setup_machphys_mapping() again in the resume path will avoid > > the crash. > > Oh, duh! > > Let me queue that up for 3.0-rc7 unless there are objections? It's not so much an objection to this patch but this issue seems to have been caused by Xen cset 20892:d311d1efc25e which looks to me like a subtle ABI breakage for guests. Perhaps we should introduce a feature flag to indicate that a guest can cope with the m2p changing size over migration like this? Ian. > > > > > Signed-off-by: Olaf Hering > > > > --- > > arch/x86/xen/mmu.c | 2 +- > > arch/x86/xen/suspend.c | 2 ++ > > 2 files changed, 3 insertions(+), 1 deletion(-) > > > > Index: linux-3.0-rc7/arch/x86/xen/mmu.c > > =================================================================== > > --- linux-3.0-rc7.orig/arch/x86/xen/mmu.c > > +++ linux-3.0-rc7/arch/x86/xen/mmu.c > > @@ -1623,7 +1623,7 @@ static void __init xen_map_identity_earl > > set_page_prot(pmd, PAGE_KERNEL_RO); > > } > > > > -void __init xen_setup_machphys_mapping(void) > > +void xen_setup_machphys_mapping(void) > > { > > struct xen_machphys_mapping mapping; > > unsigned long machine_to_phys_nr_ents; > > Index: linux-3.0-rc7/arch/x86/xen/suspend.c > > =================================================================== > > --- linux-3.0-rc7.orig/arch/x86/xen/suspend.c > > +++ linux-3.0-rc7/arch/x86/xen/suspend.c > > @@ -43,6 +43,8 @@ void xen_arch_hvm_post_suspend(int suspe > > > > void xen_arch_post_suspend(int suspend_cancelled) > > { > > + xen_setup_machphys_mapping(); > > + > > xen_build_mfn_list_list(); > > > > xen_setup_shared_info(); > > > > _______________________________________________ > > Xen-devel mailing list > > Xen-devel@lists.xensource.com > > http://lists.xensource.com/xen-devel > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel