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[Qemu-devel] vmstate: struct (VMS_STRUCT) migration
From: |
Alexey Kardashevskiy |
Subject: |
[Qemu-devel] vmstate: struct (VMS_STRUCT) migration |
Date: |
Wed, 25 Jun 2014 16:36:59 +1000 |
User-agent: |
Mozilla/5.0 (X11; Linux i686 on x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 |
Hi!
VMStateDescription supports enclosed VMStateDescription's via .vmsd. This
is used in multiple places and VMStateDescription definitions look the same
way - name, version_id, minimum_version_id, etc.
QEMU handles first level VMStateDescription and enclosed VMStateDescription
slightly different - for the latter it ignores the version_id from the
source and always uses the version_id on the destination side so version
fields are useless (code is below).
Is that by design? Or a bug? I cannot see how we could fix it without
breaking backward compatibility but I am sure the community does know that :)
If this is by design, it probably makes sense to remove unused
version_id/minimum_version_id fields completely for vmsd's which we know
are enclosed (or embedded?).
What do I miss here? Thanks!
int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
void *opaque, int version_id)
{
VMStateField *field = vmsd->fields;
int ret;
if (version_id > vmsd->version_id) {
return -EINVAL;
}
if (version_id < vmsd->minimum_version_id) {
if (vmsd->load_state_old &&
version_id >= vmsd->minimum_version_id_old) {
return vmsd->load_state_old(f, opaque, version_id);
}
return -EINVAL;
}
if (vmsd->pre_load) {
int ret = vmsd->pre_load(opaque);
if (ret) {
return ret;
}
}
while (field->name) {
if ((field->field_exists &&
field->field_exists(opaque, version_id)) ||
(!field->field_exists &&
field->version_id <= version_id)) {
void *base_addr = vmstate_base_addr(opaque, field, true);
int i, n_elems = vmstate_n_elems(opaque, field);
int size = vmstate_size(opaque, field);
for (i = 0; i < n_elems; i++) {
void *addr = base_addr + size * i;
if (field->flags & VMS_ARRAY_OF_POINTER) {
addr = *(void **)addr;
}
if (field->flags & VMS_STRUCT) {
ret = vmstate_load_state(f, field->vmsd, addr,
field->vmsd->version_id);
--
Alexey
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