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migration: Add post_save function to VMStateDescription

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In some cases it may be helpful to modify state before saving it for
migration, and then modify the state back after it has been saved. The
existing pre_save function provides half of this functionality. This
patch adds a post_save function to provide the second half.

Signed-off-by: Aaron Lindsay <aclindsa@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 20181211151945.29137-2-aaron@os.amperecomputing.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Aaron Lindsay 2019-01-21 10:23:13 +00:00 committed by Peter Maydell
parent 8733d762d5
commit 8c07559fc7
3 changed files with 20 additions and 3 deletions
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9
docs/devel/migration.rst
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@ -419,8 +419,13 @@ The functions to do that are inside a vmstate definition, and are called:
This function is called before we save the state of one device.
Example: You can look at hpet.c, that uses the three function to
massage the state that is transferred.
- ``int (*post_save)(void *opaque);``
This function is called after we save the state of one device
(even upon failure, unless the call to pre_save returned an error).
Example: You can look at hpet.c, that uses the first three functions
to massage the state that is transferred.
The ``VMSTATE_WITH_TMP`` macro may be useful when the migration
data doesn't match the stored device data well; it allows an

1
include/migration/vmstate.h
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@ -185,6 +185,7 @@ struct VMStateDescription {
int (*pre_load)(void *opaque);
int (*post_load)(void *opaque, int version_id);
int (*pre_save)(void *opaque);
int (*post_save)(void *opaque);
bool (*needed)(void *opaque);
const VMStateField *fields;
const VMStateDescription **subsections;

13
migration/vmstate.c
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@ -390,6 +390,9 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
if (ret) {
error_report("Save of field %s/%s failed",
vmsd->name, field->name);
if (vmsd->post_save) {
vmsd->post_save(opaque);
}
return ret;
}
@ -415,7 +418,15 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
json_end_array(vmdesc);
}
return vmstate_subsection_save(f, vmsd, opaque, vmdesc);
ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc);
if (vmsd->post_save) {
int ps_ret = vmsd->post_save(opaque);
if (!ret) {
ret = ps_ret;
}
}
return ret;
}
static const VMStateDescription *