The loader side of ptr marker is pretty straightforward, instead of playing
the inner_field trick, just do the load manually assuming the marker layout
is a stable ABI (which it is true already).

This will remove some logic while loading VMSD, and hopefully it makes it
slightly easier to read.  Unfortunately, we still need to keep the sender
side because of the JSON blob we're maintaining..

This paves way for future processing of non-NULL markers as well.

Signed-off-by: Peter Xu <[email protected]>
---
 migration/vmstate-types.c | 12 ++++--------
 migration/vmstate.c       | 40 ++++++++++++++++++++++++---------------
 2 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index b31689fc3c..ae465c5c2c 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -363,14 +363,10 @@ static bool load_ptr_marker(QEMUFile *f, void *pv, size_t 
size,
                             const VMStateField *field, Error **errp)
 
 {
-    int byte = qemu_get_byte(f);
-
-    if (byte == VMS_MARKER_PTR_NULL || byte == VMS_MARKER_PTR_VALID) {
-        /* TODO: process PTR_VALID case */
-        return true;
-    }
-
-    error_setg(errp, "%s: unexpected ptr marker: %d", __func__, byte);
+    /*
+     * Load is done in vmstate core, see vmstate_ptr_marker_load().
+     */
+    g_assert_not_reached();
     return false;
 }
 
diff --git a/migration/vmstate.c b/migration/vmstate.c
index a3a5f25946..d65fc84dfa 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -142,6 +142,21 @@ static void vmstate_handle_alloc(void *ptr, const 
VMStateField *field,
     }
 }
 
+static bool vmstate_ptr_marker_load(QEMUFile *f, bool *load_field,
+                                    Error **errp)
+{
+    int byte = qemu_get_byte(f);
+
+    if (byte == VMS_MARKER_PTR_NULL) {
+        /* When it's a null ptr marker, do not continue the load */
+        *load_field = false;
+        return true;
+    }
+
+    error_setg(errp, "Unexpected ptr marker: %d", byte);
+    return false;
+}
+
 static bool vmstate_pre_load(const VMStateDescription *vmsd, void *opaque,
                              Error **errp)
 {
@@ -264,30 +279,25 @@ bool vmstate_load_vmsd(QEMUFile *f, const 
VMStateDescription *vmsd,
             }
 
             for (i = 0; i < n_elems; i++) {
-                bool ok;
+                /* If we will process the load of field? */
+                bool load_field = true;
+                bool ok = true;
                 void *curr_elem = first_elem + size * i;
-                const VMStateField *inner_field;
 
                 if (field->flags & VMS_ARRAY_OF_POINTER) {
                     curr_elem = *(void **)curr_elem;
                 }
 
                 if (!curr_elem && size) {
-                    /*
-                     * If null pointer found (which should only happen in
-                     * an array of pointers), use null placeholder and do
-                     * not follow.
-                     */
-                    inner_field = vmsd_create_ptr_marker_field(field);
-                } else {
-                    inner_field = field;
+                    /* Read the marker instead of VMSD itself */
+                    if (!vmstate_ptr_marker_load(f, &load_field, errp)) {
+                        trace_vmstate_load_field_error(field->name, -EINVAL);
+                        return false;
+                    }
                 }
 
-                ok = vmstate_load_field(f, curr_elem, size, inner_field, errp);
-
-                /* If we used a fake temp field.. free it now */
-                if (inner_field != field) {
-                    g_clear_pointer((gpointer *)&inner_field, g_free);
+                if (load_field) {
+                    ok = vmstate_load_field(f, curr_elem, size, field, errp);
                 }
 
                 if (ok) {
-- 
2.50.1


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