From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34795) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eizpn-0008NQ-8Q for qemu-devel@nongnu.org; Tue, 06 Feb 2018 04:46:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eizpi-0008Sx-NK for qemu-devel@nongnu.org; Tue, 06 Feb 2018 04:46:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50836) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eizpi-0008SF-DN for qemu-devel@nongnu.org; Tue, 06 Feb 2018 04:46:34 -0500 Date: Tue, 6 Feb 2018 09:46:28 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20180206094628.GA2462@work-vm> References: <151790197381.27004.13241184632371976036.stgit@bahia.lan> <9f1237f2-5194-1cc5-dbc4-b453ff3ee7c4@virtuozzo.com> <20180206094310.2a9cdc5c@bahia.lan> <37d2afca-0b5a-8c69-4caf-8e0c190cba7e@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37d2afca-0b5a-8c69-4caf-8e0c190cba7e@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH] migration: incoming postcopy advise sanity checks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vladimir Sementsov-Ogievskiy Cc: Greg Kurz , qemu-devel@nongnu.org, Juan Quintela * Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote: > 06.02.2018 11:43, Greg Kurz wrote: > > On Tue, 6 Feb 2018 10:49:47 +0300 > > Vladimir Sementsov-Ogievskiy wrote: > > > > > 06.02.2018 10:26, Greg Kurz 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 > > > > --- > > > > migration/savevm.c | 18 +++++++++++++++--- > > > > 1 file changed, 15 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/migration/savevm.c b/migration/savevm.c > > > > index b7908f62be3c..1c516fcbb8d7 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 +1388,19 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis) > > > > return -1; > > > > } > > > > - if (!migrate_postcopy_ram()) { > > > > + switch (len) { > > > > + case 0: > > > > + /* The source hasn't enabled postcopy-ram. Nothing to do. */ > > > should we error-out here if (migrate_postcopy_ram()) ? > > > > > I was also thinking so at first, but if the source hasn't enabled postcopy-ram, > > then RAM postcopy won't happen. Not sure why we should error out... > > if user enables dirty-bitmaps postcopy on source, and enables postcopy-ram > on target, > we will be here, with migrate_postcopy_ram()=true. and it should be error. In that case it's probably worth it. > > > > > > return 0; > > > > + case 8 + 8: > > > > + if (!migrate_postcopy_ram()) { > > > > + error_report("RAM postcopy is disabled"); Can you make that a little bit more descriptive please: error_report("RAM postcopy is disabled but have 16 byte advise"); should do. Thanks, Dave > > > > + return -EINVAL; > > > > + } > > > > + break; > > > > + default: > > > > + error_report("CMD_POSTCOPY_ADVISE invalid length (%d)", len); > > > > + return -EINVAL; > > > > } > > > > if (!postcopy_ram_supported_by_host(mis)) { > > > > @@ -1807,7 +1819,7 @@ 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); > > > > > > -- > Best regards, > Vladimir > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK