From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: live migration question Date: Tue, 31 Jan 2012 08:50:46 +0100 Message-ID: <4F279D56.3030303@ts.fujitsu.com> References: <4F268C03.5000003@ts.fujitsu.com> <4F26D2A8020000780006FF2F@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F26D2A8020000780006FF2F@nat28.tlf.novell.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: Jan Beulich Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 01/30/2012 05:26 PM, Jan Beulich wrote: >>>> On 30.01.12 at 13:24, Juergen Gross wrote: >> To avoid this stall I tried to start a little daemon on the target machine >> and watch for a new BS2000 domain to show up due to live migration. I wanted >> to map the domain memory as soon as the needed mapping information located >> in a fixed guest mfn was transferred. Discovery of the new domain works as >> expected, but I'm not capable doing any memory mapping until the restore of >> the domain is finished. The mapping ioctl using IOCTL_PRIVCMD_MMAP returns >> EINVAL until xc_restore is finished (more or less). >> >> Why can xc_restore do the mapping while I can't? I know xc_restore is using >> IOCTL_PRIVCMD_MMAPBATCH_V2, but I can't see a difference which should matter >> between those two, as both are using the same hypercall to update the dom0 >> page tables. > I cannot immediately think of a reason (and indeed the difference > between the two is only how errors get handled), so I wonder > whether you checked where the - pretty generic - -EINVAL is > coming from. You also didn't mention whether any hypervisor log > entries are associated with you failed attempts. I'll start to add some logging to the hypervisor today. No hypervisor logs were produced in my tests, despite of setting debug=yes loglvl=all guest_loglvl=all as boot parameters. I've made an additional test using xm save/xm restore to see if the same problem shows up. It does NOT. Mapping succeeds at once while restoring memory is still running. I always thought xm restore and live migration on the target machine are more or less the same. This seems not to be true. Juergen -- Juergen Gross Principal Developer Operating Systems PDG ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967 Fujitsu Technology Solutions e-mail: juergen.gross@ts.fujitsu.com Domagkstr. 28 Internet: ts.fujitsu.com D-80807 Muenchen Company details: ts.fujitsu.com/imprint.html