From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: xm save fails to save all pages Date: Tue, 25 Oct 2011 14:32:55 +0100 Message-ID: References: <4EA6B68C.8050404@ts.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4EA6B68C.8050404@ts.fujitsu.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Juergen Gross , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 25/10/2011 14:15, "Juergen Gross" wrote: > in preparation to support live migration for BS2000 I'm testing my domU (HVM > with PV-drivers) with xm save/restore. I'm running xen 4.0.2 (from SLES11 > SP1). > > During xm save I see the following line in xend.log: > > [2011-10-25 13:25:25 31519] INFO (XendCheckpoint:484) Saving memory pages: > iter 1 0%type fail: page 510 mfn 000011fe > > I added some diagnostic code to the hypervisor (in arch/x86/domctl.c) and > found > that the hypervisor believes gmfn 11fe of the domU is part of the xen heap. > > The problem is always reported for gmfn 11fe, regardless of the memory size of > the domU: I tried 1, 2 and 8 GB. The memory page isn't used for anything > special in the domU, there is no problem accessing it or mapping it to dom0 > before doing the xm save (or after xm save -c). > > When I try to restore the saved domain I can't map gmfn 11fe of the domU any > longer in dom0 (this was the first hint there is a problem at all). > > How can a domU memory page be part of the xen heap? It could be the domain's shared-info page, or one of its grant-table pages. It doesn't make sense to save/restore such pages -- they get reconstructed appropriately on the receiving end, by the toolstack and/or by the domain itself when it resumes execution. -- Keir