From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60208) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ej1J2-000639-Se for qemu-devel@nongnu.org; Tue, 06 Feb 2018 06:20:59 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ej1Iw-00039L-Uc for qemu-devel@nongnu.org; Tue, 06 Feb 2018 06:20:56 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46566) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ej1Iw-00038l-Lb for qemu-devel@nongnu.org; Tue, 06 Feb 2018 06:20:50 -0500 Date: Tue, 6 Feb 2018 11:20:46 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20180206112045.GC2462@work-vm> References: <151791154436.32601.15403203498591276038.stgit@bahia.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <151791154436.32601.15403203498591276038.stgit@bahia.lan> Subject: Re: [Qemu-devel] [PATCH v2] migration: incoming postcopy advise sanity checks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: qemu-devel@nongnu.org, Juan Quintela , Vladimir Sementsov-Ogievskiy * Greg Kurz (groug@kaod.org) wrote: > If postcopy-ram was set on the source but not on the destination, > migration doesn't occur, the destination prints an error and boots > the guest: > > qemu-system-ppc64: Expected vmdescription section, but got 0 > > We end up with two running instances. > > This behaviour was introduced in 2.11 by commit 58110f0acb1a "migration: > split common postcopy out of ram postcopy" to prepare ground for the > upcoming dirty bitmap postcopy support. It adds a new case where the > source may send an empty postcopy advise because dirty bitmap doesn't > need to check page sizes like RAM postcopy does. > > If the source has enabled postcopy-ram, then it sends an advise with > the page size values. If the destination hasn't enabled postcopy-ram, > then loadvm_postcopy_handle_advise() leaves the page size values on > the stream and returns. This confuses qemu_loadvm_state() later on > and causes the destination to start execution. > > As discussed several times, postcopy-ram should be enabled both sides > to be functional. This patch changes the destination to perform some > extra checks on the advise length to ensure this is the case. Otherwise > an error is returned and migration is aborted. > > Reported-by: Balamuruhan S > Signed-off-by: Greg Kurz Thanks for finding and fixing this. Queued. Dave > --- > v2: - error out if postcopy-ram is enabled but the source hasn't sent the > expected 16 byte advise > - more descriptive message if postcopy-ram is disabled but the source > has sent a 16 byte advise > --- > migration/savevm.c | 21 ++++++++++++++++++--- > 1 file changed, 18 insertions(+), 3 deletions(-) > > diff --git a/migration/savevm.c b/migration/savevm.c > index b7908f62be3c..e97671c1f7bd 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -1376,7 +1376,8 @@ static int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis); > * *might* happen - it might be skipped if precopy transferred everything > * quickly. > */ > -static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis) > +static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis, > + uint16_t len) > { > PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_ADVISE); > uint64_t remote_pagesize_summary, local_pagesize_summary, remote_tps; > @@ -1387,8 +1388,22 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis) > return -1; > } > > - if (!migrate_postcopy_ram()) { > + switch (len) { > + case 0: > + if (migrate_postcopy_ram()) { > + warn_report("RAM postcopy is enabled but have 0 byte advise"); > + return -EINVAL; > + } > return 0; > + case 8 + 8: > + if (!migrate_postcopy_ram()) { > + error_report("RAM postcopy is disabled but have 16 byte advise"); > + return -EINVAL; > + } > + break; > + default: > + error_report("CMD_POSTCOPY_ADVISE invalid length (%d)", len); > + return -EINVAL; > } > > if (!postcopy_ram_supported_by_host(mis)) { > @@ -1807,7 +1822,7 @@ static int loadvm_process_command(QEMUFile *f) > return loadvm_handle_cmd_packaged(mis); > > case MIG_CMD_POSTCOPY_ADVISE: > - return loadvm_postcopy_handle_advise(mis); > + return loadvm_postcopy_handle_advise(mis, len); > > case MIG_CMD_POSTCOPY_LISTEN: > return loadvm_postcopy_handle_listen(mis); > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK