From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58223) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eeH19-0007SS-G8 for qemu-devel@nongnu.org; Wed, 24 Jan 2018 04:06:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eeH14-0000C4-Ek for qemu-devel@nongnu.org; Wed, 24 Jan 2018 04:06:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53370) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eeH14-00009l-8z for qemu-devel@nongnu.org; Wed, 24 Jan 2018 04:06:46 -0500 Date: Wed, 24 Jan 2018 09:06:34 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20180124090633.GB2496@work-vm> References: <20171205065307.21853-1-peterx@redhat.com> <20171205065307.21853-27-peterx@redhat.com> <20171219105859.GC2730@work-vm> <20180124082817.GF8001@xz-mi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180124082817.GF8001@xz-mi> Subject: Re: [Qemu-devel] [PATCH v5 26/28] migration: allow migrate_cancel to pause postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: qemu-devel@nongnu.org, Andrea Arcangeli , "Daniel P . Berrange" , Juan Quintela , Alexey Perevalov * Peter Xu (peterx@redhat.com) wrote: > On Tue, Dec 19, 2017 at 10:58:59AM +0000, Dr. David Alan Gilbert wrote: > > * Peter Xu (peterx@redhat.com) wrote: > > > It was allowed in the past to even cancel a postcopy migration, but it > > > does not really make sense, and no one should be using it, since > > > cancelling a migration during postcopy means crashing the VM at no time. > > > > > > Let's just use re-use this command as a way to pause the postcopy > > > migration when we detected that we are in postcopy migration. This can > > > be used when we want to trigger the postcopy recovery manually. > > > > > > Signed-off-by: Peter Xu > > > > Yes, OK, this is a little odd without having any flags or anything, but > > it's essentially the saem reason that cancel exists - to stop a > > migration we know that's broken for some reason. > > > > (I could argue whether this should be special cased in migrate_fd_cancel > > instead, but that's just a preference). > > > > > > Reviewed-by: Dr. David Alan Gilbert > > Firstly, thanks for the r-b. > > Now after knowing your iptable test, I think we reached a consensus > that we need to provide a command (for example, reuse migrate-cancel) > to allow destination to shutdown its incoming migration port too. At > the same time, if we want to make sure the command can always work on > destination, we'd better also let that command to be OOB-capable. > > However I'm not sure whether I can let migrate-cancel be OOB-capable > since recently we added bdrv_invalidate_cache_all() into > migrate_fd_cancel(). That invalidation needs some mutex which might > block. I don't know whether it means migrate-cancel will no longer be > suitable as an OOB command now. > > So, maybe now I can do this: firstly, drop this patch; then add a new > command to do the shutdown explicitly (allow either src/dst to > shutdown its migration fd) and keep migrate-cancel untouched. In that > case, I can make sure the new command will be OOB-compatible. > > What do you think? Yes I'm fine with that; misusing another command did feel a bit odd. Dave > -- > Peter Xu -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK