From: Peter Maydell peter.mayd...@linaro.org
At the moment we require vmstate definitions to set minimum_version_id_old
to the same value as minimum_version_id if they do not provide a
load_state_old handler. Since the load_state_old functionality is
required only for a handful of devices that need to retain migration
compatibility with a pre-vmstate implementation, this means the bulk
of devices have pointless boilerplate. Relax the definition so that
minimum_version_id_old is ignored if there is no load_state_old handler.
Note that under the old scheme we would segfault if the vmstate
specified a minimum_version_id_old that was less than minimum_version_id
but did not provide a load_state_old function, and the incoming state
specified a version number between minimum_version_id_old and
minimum_version_id. Under the new scheme this will just result in
our failing the migration.
Signed-off-by: Peter Maydell peter.mayd...@linaro.org
Reviewed-by: Michael S. Tsirkin m...@redhat.com
Signed-off-by: Michael S. Tsirkin m...@redhat.com
---
vmstate.c | 9 +
docs/migration.txt | 12 +---
2 files changed, 10 insertions(+), 11 deletions(-)
diff --git a/vmstate.c b/vmstate.c
index dbb7666..b5882fa 100644
--- a/vmstate.c
+++ b/vmstate.c
@@ -63,11 +63,12 @@ int vmstate_load_state(QEMUFile *f, const
VMStateDescription *vmsd,
if (version_id vmsd-version_id) {
return -EINVAL;
}
-if (version_id vmsd-minimum_version_id_old) {
-return -EINVAL;
-}
if (version_id vmsd-minimum_version_id) {
-return vmsd-load_state_old(f, opaque, 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);
diff --git a/docs/migration.txt b/docs/migration.txt
index 0e0a1d4..fe1f2bb 100644
--- a/docs/migration.txt
+++ b/docs/migration.txt
@@ -139,7 +139,6 @@ static const VMStateDescription vmstate_kbd = {
.name = pckbd,
.version_id = 3,
.minimum_version_id = 3,
-.minimum_version_id_old = 3,
.fields = (VMStateField []) {
VMSTATE_UINT8(write_cmd, KBDState),
VMSTATE_UINT8(status, KBDState),
@@ -168,12 +167,13 @@ You can see that there are several version fields:
- minimum_version_id: the minimum version_id that VMState is able to understand
for that device.
- minimum_version_id_old: For devices that were not able to port to vmstate,
we can
- assign a function that knows how to read this old state.
+ assign a function that knows how to read this old state. This field is
+ ignored if there is no load_state_old handler.
So, VMState is able to read versions from minimum_version_id to
-version_id. And the function load_state_old() is able to load state
-from minimum_version_id_old to minimum_version_id. This function is
-deprecated and will be removed when no more users are left.
+version_id. And the function load_state_old() (if present) is able to
+load state from minimum_version_id_old to minimum_version_id. This
+function is deprecated and will be removed when no more users are left.
=== Massaging functions ===
@@ -255,7 +255,6 @@ const VMStateDescription vmstate_ide_drive_pio_state = {
.name = ide_drive/pio_state,
.version_id = 1,
.minimum_version_id = 1,
-.minimum_version_id_old = 1,
.pre_save = ide_drive_pio_pre_save,
.post_load = ide_drive_pio_post_load,
.fields = (VMStateField []) {
@@ -275,7 +274,6 @@ const VMStateDescription vmstate_ide_drive = {
.name = ide_drive,
.version_id = 3,
.minimum_version_id = 0,
-.minimum_version_id_old = 0,
.post_load = ide_drive_post_load,
.fields = (VMStateField []) {
several fields
--
MST
