From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59560) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eiy0s-0001ao-0h for qemu-devel@nongnu.org; Tue, 06 Feb 2018 02:49:59 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eiy0o-0001D9-UV for qemu-devel@nongnu.org; Tue, 06 Feb 2018 02:49:58 -0500 Received: from mail-ve1eur01on0103.outbound.protection.outlook.com ([104.47.1.103]:58175 helo=EUR01-VE1-obe.outbound.protection.outlook.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eiy0o-0001CZ-7t for qemu-devel@nongnu.org; Tue, 06 Feb 2018 02:49:54 -0500 References: <151790197381.27004.13241184632371976036.stgit@bahia.lan> From: Vladimir Sementsov-Ogievskiy Message-ID: <9f1237f2-5194-1cc5-dbc4-b453ff3ee7c4@virtuozzo.com> Date: Tue, 6 Feb 2018 10:49:47 +0300 MIME-Version: 1.0 In-Reply-To: <151790197381.27004.13241184632371976036.stgit@bahia.lan> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Subject: Re: [Qemu-devel] [PATCH] migration: incoming postcopy advise sanity checks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz , qemu-devel@nongnu.org Cc: "Dr. David Alan Gilbert" , Juan Quintela 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()) ? > return 0; > + case 8 + 8: > + if (!migrate_postcopy_ram()) { > + error_report("RAM postcopy is disabled"); > + 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