From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47346) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dwn0G-0007WH-Ai for qemu-devel@nongnu.org; Tue, 26 Sep 2017 06:22:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dwn0F-0004Si-Gj for qemu-devel@nongnu.org; Tue, 26 Sep 2017 06:22:12 -0400 Date: Tue, 26 Sep 2017 11:21:50 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20170926102150.GD2689@work-vm> References: <1078f013-e554-1d75-d1e8-f24daace5965@virtuozzo.com> <20170919190634.GK2107@work-vm> <87bmm5k2zs.fsf@secure.laptop> <20170925132312.GA7999@localhost.localdomain> <20170925145842.GB7999@localhost.localdomain> <20170925152735.GG2656@work-vm> <20170926101245.GB3399@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170926101245.GB3399@localhost.localdomain> Subject: Re: [Qemu-devel] ping Re: [PATCH v7 03/16] migration: split common postcopy out of ram postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: Vladimir Sementsov-Ogievskiy , Juan Quintela , peter.maydell@linaro.org, famz@redhat.com, stefanha@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, armbru@redhat.com, lirans@il.ibm.com, pbonzini@redhat.com, den@openvz.org, mreitz@redhat.com, John Snow * Kevin Wolf (kwolf@redhat.com) wrote: > Am 25.09.2017 um 17:27 hat Dr. David Alan Gilbert geschrieben: > > > > Whatever you think the preferred way to set up postcopy migration is: If > > > > something worked before this patch and doesn't after it, that's a > > > > regression and breaks backwards compatibility. > > > > > > > > If we were talking about a graceful failure, maybe we could discuss > > > > whether carefully and deliberately breaking compatibility could be > > > > justified in this specific case. But the breakage is neither mentioned > > > > in the commit message nor is it graceful, so I can only call it a bug. > > > > > > > > Kevin > > > > > > It's of course my fault, I don't mean "it's wrong test, so it's not my > > > problem") And I've already sent a patch. > > > > Why does this fail so badly, asserts etc - I was hoping for something > > a bit more obvious from the migration code. > > > > postcopy did originally work without the destination having the flag on > > but setting the flag on the destination was always good practice because > > it detected whether the host support was there early on. > > So what does this mean for 2.11? Do you think it is acceptable breaking > cases where the flag isn't set on the destination? I think so, because we've always recommended setting it on the destination for the early detection. > If so, just changing the test case is enough. But if not, I'd rather > keep the test case as it is and fix only the migration code. I'd take the test case fix, but I also want to dig why it fails so badly; it would be nice just to have a clean failure telling you that postcopy was expected. Dave > > Kevin -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK