From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: Migration with linear p2m list Date: Thu, 3 Dec 2015 09:37:50 +0000 Message-ID: <56600D6E.4010601@citrix.com> References: <565FF233.5040302@suse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <565FF233.5040302@suse.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Juergen Gross , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 03/12/15 07:41, Juergen Gross wrote: > I'm just working on a patch series to support migration via using > the virtual mapped linear p2m list. Migration seems to work quite > nice and now I'm looking into how to support changes of the p2m > list structure during migration. For this purpose we introduced > p2m_generation in the shared info structure which is incremented > by the guest in case of changing a mapping of the p2m list. > > The question is: what kind of support should I add initially: > > 1) none: same as for the p2m tree used today > > 2) minimal: detect a change and cancel migration in this case > > 3) medium: detect a change and restart migration (limited by a > retry count) > > 4) full: detect a change and adapt the current migration to it > (remap p2m list, resend it to receive side, adapt logdirty > map) > > As such a change should be rare I'm currently heading for the > minimal solution. Full support could be added later independent > from the initial p2m list support. Any thoughts? I would also opt for 2 to start with. There is a substantial quantity of other infrastructure required to correctly send an update once you have noticed that something has changed. It would be better not to conflate the two issues. ~Andrew