From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57187) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dwp2N-0007v4-SX for qemu-devel@nongnu.org; Tue, 26 Sep 2017 08:32:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dwp2M-0005SD-OK for qemu-devel@nongnu.org; Tue, 26 Sep 2017 08:32:31 -0400 Date: Tue, 26 Sep 2017 14:32:03 +0200 From: Kevin Wolf Message-ID: <20170926123203.GA14717@localhost.localdomain> 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> <20170926102150.GD2689@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170926102150.GD2689@work-vm> 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: "Dr. David Alan Gilbert" 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 Am 26.09.2017 um 12:21 hat Dr. David Alan Gilbert geschrieben: > * 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. Okay, I'll include the test case patch in my pull request today then. > > 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. Yes, that would be nice. Kevin