From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38936) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEhIc-00047V-Li for qemu-devel@nongnu.org; Mon, 13 Jul 2015 13:13:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZEhIZ-0005Op-BS for qemu-devel@nongnu.org; Mon, 13 Jul 2015 13:13:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37469) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEhIZ-0005Ok-3y for qemu-devel@nongnu.org; Mon, 13 Jul 2015 13:13:47 -0400 Date: Mon, 13 Jul 2015 18:13:40 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20150713171340.GK2492@work-vm> References: <1434450415-11339-1-git-send-email-dgilbert@redhat.com> <1434450415-11339-23-git-send-email-dgilbert@redhat.com> <87380sl2rx.fsf@neno.neno> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87380sl2rx.fsf@neno.neno> Subject: Re: [Qemu-devel] [PATCH v7 22/42] migrate_start_postcopy: Command to trigger transition to postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Juan Quintela Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, amit.shah@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au * Juan Quintela (quintela@redhat.com) wrote: > "Dr. David Alan Gilbert (git)" wrote: > > From: "Dr. David Alan Gilbert" > > > > Once postcopy is enabled (with migrate_set_capability), the migration > > will still start on precopy mode. To cause a transition into postcopy > > the: > > > > migrate_start_postcopy > > > > command must be issued. Postcopy will start sometime after this > > (when it's next checked in the migration loop). > > > > Issuing the command before migration has started will error, > > and issuing after it has finished is ignored. > > > > Signed-off-by: Dr. David Alan Gilbert > > Reviewed-by: Eric Blake > > > diff --git a/include/migration/migration.h b/include/migration/migration.h > > index a5951ac..e973490 100644 > > --- a/include/migration/migration.h > > +++ b/include/migration/migration.h > > @@ -111,6 +111,9 @@ struct MigrationState > > int64_t xbzrle_cache_size; > > int64_t setup_time; > > int64_t dirty_sync_count; > > + > > + /* Flag set once the migration has been asked to enter postcopy */ > > + bool start_postcopy; > > }; > > > > void process_incoming_migration(QEMUFile *f); > > diff --git a/migration/migration.c b/migration/migration.c > > index e77b8b4..6fc47f9 100644 > > --- a/migration/migration.c > > +++ b/migration/migration.c > > @@ -465,6 +465,28 @@ void qmp_migrate_set_parameters(bool has_compress_level, > > } > > } > > > > +void qmp_migrate_start_postcopy(Error **errp) > > +{ > > + MigrationState *s = migrate_get_current(); > > + > > + if (!migrate_postcopy_ram()) { > > + error_setg(errp, "Enable postcopy with migration_set_capability before" > > + " the start of migration"); > > + return; > > + } > > + > > + if (s->state == MIGRATION_STATUS_NONE) { > > I would claim that this check should be: > > if (s->state != MIGRATION_STATUS_ACTIVE) { > ?? > > FAILED, COMPLETED, CANCELL* don't make sense, right? What I'm trying to catch here is people doing: migrate_start_postcopy migrate tcp:pppp:whereever which wont work, because migrate_init reinitialises the flag that start previously set. However, I also don't want to create a race, since what you do is typically: migrate tcp:pppp:whereever migrate_start_postcopy if you're unlucky, and the migration finishes just at the same time you do the migrate_start_postcopy, do you want migrate_start_postcopy to fail? My guess was it was best for it not to fail, in this case. Dave > > Thanks, Juan. -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK