For virtio-mem, we want to have the plugged/unplugged state of memory
blocks available before migrating any actual RAM content. This
information is immutable on the migration source while migration is active,
For example, we want to use this information for proper preallocation
support with migration: currently, we don't preallocate memory on the
migration target, and especially with hugetlb, we can easily run out of
hugetlb pages during RAM migration and will crash (SIGBUS) instead of
catching this gracefully via preallocation.
Migrating device state before we start iterating is currently impossible.
Introduce and use qemu_savevm_state_start_precopy(), and use
a new special migration priority -- MIG_PRI_POST_SETUP -- to decide whether
state will be saved in qemu_savevm_state_start_precopy() or in
qemu_savevm_state_complete_precopy_*().
We have to take care of properly including the early device state in the
vmdesc. Relying on migrate_get_current() to temporarily store the vmdesc is
a bit sub-optimal, but we use that explicitly or implicitly all over the
place already, so this barely matters in practice.
Note that only very selected devices (i.e., ones seriously messing with
RAM setup) are supposed to make use of that.
Signed-off-by: David Hildenbrand <david@redhat.com>
if (inactivate_disks) {
@@ -1427,6 +1474,10 @@ int
qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
qemu_put_buffer(f, (uint8_t *)json_writer_get(vmdesc), vmdesc_len);
}
+ /* Free it now to detect any inconsistencies. */
+ g_free(vmdesc);