From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:50736) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QroZA-0002MW-LW for qemu-devel@nongnu.org; Fri, 12 Aug 2011 06:02:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QroZ9-0002Kq-Mi for qemu-devel@nongnu.org; Fri, 12 Aug 2011 06:02:12 -0400 Received: from mail-qw0-f45.google.com ([209.85.216.45]:61070) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QroZ9-0002Kj-KV for qemu-devel@nongnu.org; Fri, 12 Aug 2011 06:02:11 -0400 Received: by qwj8 with SMTP id 8so1801752qwj.4 for ; Fri, 12 Aug 2011 03:02:11 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini Date: Fri, 12 Aug 2011 11:59:37 +0200 Message-Id: <1313143181-7921-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH v3 0/4] Fix subsection ambiguity in the migration format List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org With the current migration format, VMS_STRUCTs with subsections are ambiguous. The protocol cannot tell whether a 0x5 byte after the VMS_STRUCT is a subsection or part of the parent data stream. In the past QEMU assumed it was always a part of a subsection; after commit eb60260 (savevm: fix corruption in vmstate_subsection_load(), 2011-02-03) the choice depends on whether the VMS_STRUCT has subsections defined. Unfortunately, this means that if a destination has no subsections defined for the struct, it will happily read subsection data into its own fields. And if you are "lucky" enough to stumble on a zero byte at the right time, it will be interpreted as QEMU_VM_EOF and migration will be interrupted with half-loaded state. There is no way out of this except defining an incompatible migration protocol; a sentinel at the end of embedded structs is enough to remove the ambiguity, but is already incompatible of course. So this can be restricted to new machine models, and this is what the patch series does. (Only patch 3 is specific to the short-term solution, everything else is entirely generic). v2->v3 resolve conflicts, move savevm.o to libhw v1->v2 coding style Paolo Bonzini (4): add support for machine models to specify their migration format add pc-0.14/pc-0.15 machine savevm: define new unambiguous migration format Partially revert "savevm: fix corruption in vmstate_subsection_load()." Makefile.objs | 4 ++-- hw/boards.h | 4 ++++ hw/pc_piix.c | 16 +++++++++++++++- savevm.c | 44 ++++++++++++++++++++++++++++++-------------- 4 files changed, 51 insertions(+), 17 deletions(-) -- 1.7.6