From 875fcd013ab68c64802998b22f54f0184479d21b Mon Sep 17 00:00:00 2001 From: Greg Kurz Date: Tue, 6 Feb 2018 12:23:30 +0100 Subject: [PATCH] migration: incoming postcopy advise sanity checks 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 Reviewed-by: Daniel Henrique Barboza Reviewed-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Dr. David Alan Gilbert Message-Id: <151791621042.19120.3103118434734245776.stgit@bahia> Signed-off-by: Dr. David Alan Gilbert --- migration/savevm.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/migration/savevm.c b/migration/savevm.c index b024ee3b22..f202c3de3a 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()) { + error_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);