[PATCH V3 03/42] migration: lower handler priority

[Steve Sistare]

Define a vmstate priority that is lower than the default, so its handlers
run after all default priority handlers.  Since 0 is no longer the default
priority, translate an uninitialized priority of 0 to MIG_PRI_DEFAULT.

CPR for vfio will use this to install handlers for containers that run
after handlers for the devices that they contain.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
---
 include/migration/vmstate.h | 6 +++++-
 migration/savevm.c          | 4 ++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index a1dfab4..1ff7bd9 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -155,7 +155,11 @@ enum VMStateFlags {
 };
 
 typedef enum {
-    MIG_PRI_DEFAULT = 0,
+    MIG_PRI_UNINITIALIZED = 0,  /* An uninitialized priority field maps to */
+                                /* MIG_PRI_DEFAULT in save_state_priority */
+
+    MIG_PRI_LOW,                /* Must happen after default */
+    MIG_PRI_DEFAULT,
     MIG_PRI_IOMMU,              /* Must happen before PCI devices */
     MIG_PRI_PCI_BUS,            /* Must happen before IOMMU */
     MIG_PRI_VIRTIO_MEM,         /* Must happen before IOMMU */
diff --git a/migration/savevm.c b/migration/savevm.c
index 006514c..7e87815 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -266,7 +266,7 @@ typedef struct SaveState {
 
 static SaveState savevm_state = {
     .handlers = QTAILQ_HEAD_INITIALIZER(savevm_state.handlers),
-    .handler_pri_head = { [MIG_PRI_DEFAULT ... MIG_PRI_MAX] = NULL },
+    .handler_pri_head = { [0 ... MIG_PRI_MAX] = NULL },
     .global_section_id = 0,
 };
 
@@ -737,7 +737,7 @@ static int calculate_compat_instance_id(const char *idstr)
 
 static inline MigrationPriority save_state_priority(SaveStateEntry *se)
 {
-    if (se->vmsd) {
+    if (se->vmsd && se->vmsd->priority) {
         return se->vmsd->priority;
     }
     return MIG_PRI_DEFAULT;
-- 
1.8.3.1