On 06/30/2011 10:46 AM, Paolo Bonzini wrote:
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. There is no way out of this except defining an incompatible migration protocol with a sentinel at the end of embedded structs. Of course, this is restricted to new machine models. Signed-off-by: Paolo Bonzini<pbonz...@redhat.com> --- hw/pc_piix.c | 6 ++++++ savevm.c | 27 +++++++++++++++++++-------- 2 files changed, 25 insertions(+), 8 deletions(-) diff --git a/hw/pc_piix.c b/hw/pc_piix.c index 18cc942..d8d629c 100644 --- a/hw/pc_piix.c +++ b/hw/pc_piix.c @@ -271,6 +271,7 @@ static QEMUMachine pc_machine_v0_14 = { .desc = "Standard PC", .init = pc_init_pci, .max_cpus = 255, + .migration_format = 3, };
Please introduce a macro so this code is readable. We have other machines that support migration in other archs too. Regards, Anthony Liguori
