[Qemu-stable] [PATCH for-1.4 1/2] savevm: add support for RAMBlock resize handlers

[Michael Roth]

This allow users to register resize handlers to be called in cases where
a RAMBlock is received over the wire that doesn't match the size of the
target's corresponding RAMBlock. The handlers are generally responsible
for tearing down and re-initializing corresponding MemoryRegions based on
knowledge of what the size of the RAMBlock is that they'll be receiving
over the wire.

Cc: address@hidden
Signed-off-by: Michael Roth <address@hidden>
---
 arch_init.c                 |   28 +++++++++++++---
 include/migration/vmstate.h |   14 ++++++++
 savevm.c                    |   77 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 114 insertions(+), 5 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 8da868b..265ad8c 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -793,33 +793,51 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
                 ram_addr_t total_ram_bytes = addr;
 
                 while (total_ram_bytes) {
-                    RAMBlock *block;
+                    RAMBlock *block, *block_next;
                     uint8_t len;
 
                     len = qemu_get_byte(f);
                     qemu_get_buffer(f, (uint8_t *)id, len);
                     id[len] = 0;
                     length = qemu_get_be64(f);
+                    ret = 0;
 
-                    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
+                    QTAILQ_FOREACH_SAFE(block, &ram_list.blocks, next,
+                                        block_next) {
                         if (!strncmp(id, block->idstr, sizeof(id))) {
                             if (block->length != length) {
-                                ret =  -EINVAL;
-                                goto done;
+                                const VMStateRAMResizeHandler *rh =
+                                    vmstate_find_ram_resize(block->mr);
+                                if (rh) {
+                                    ret = vmstate_do_ram_resize(rh, length);
+                                } else {
+                                    ret =  -EINVAL;
+                                }
                             }
                             break;
                         }
                     }
 
+                    if (ret) {
+                        break;
+                    }
+
                     if (!block) {
                         fprintf(stderr, "Unknown ramblock \"%s\", cannot "
                                 "accept migration\n", id);
                         ret = -EINVAL;
-                        goto done;
+                        break;
                     }
 
                     total_ram_bytes -= length;
                 }
+                /* end of block synchronization phase, resize handlers are
+                 * no longer useful
+                 */
+                vmstate_unregister_ram_resizable_all();
+                if (ret) {
+                    goto done;
+                }
             }
         }
 
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index f27276c..9e50391 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -637,4 +637,18 @@ void vmstate_register_ram(struct MemoryRegion *memory, 
DeviceState *dev);
 void vmstate_unregister_ram(struct MemoryRegion *memory, DeviceState *dev);
 void vmstate_register_ram_global(struct MemoryRegion *memory);
 
+/* definitions for registering resize handlers for memory blocks */
+typedef struct VMStateRAMResizeHandler VMStateRAMResizeHandler;
+
+typedef int (RAMResizeFunc)(struct MemoryRegion *mr, uint64_t size, void 
*opaque);
+typedef void (RAMResizeCleanupFunc)(void *opaque);
+
+void vmstate_register_ram_resizable(struct MemoryRegion *mr,
+                                    RAMResizeFunc resize_func,
+                                    RAMResizeCleanupFunc cleanup_func,
+                                    void *opaque);
+void vmstate_unregister_ram_resizable_all(void);
+const VMStateRAMResizeHandler *vmstate_find_ram_resize(const struct 
MemoryRegion *mr);
+int vmstate_do_ram_resize(const VMStateRAMResizeHandler *rh, uint64_t size);
+
 #endif
diff --git a/savevm.c b/savevm.c
index 4eb29b2..0553c47 100644
--- a/savevm.c
+++ b/savevm.c
@@ -2388,3 +2388,80 @@ void vmstate_register_ram_global(MemoryRegion *mr)
 {
     vmstate_register_ram(mr, NULL);
 }
+
+/* routines for registering resize handlers for memory blocks */
+struct VMStateRAMResizeHandler {
+    MemoryRegion *mr;
+    RAMResizeFunc *resize_func;
+    RAMResizeCleanupFunc *cleanup_func;
+    void *opaque;
+    QTAILQ_ENTRY(VMStateRAMResizeHandler) next;
+};
+
+static QTAILQ_HEAD(, VMStateRAMResizeHandler) ram_resize_handlers =
+    QTAILQ_HEAD_INITIALIZER(ram_resize_handlers);
+
+void vmstate_register_ram_resizable(MemoryRegion *mr,
+                                    RAMResizeFunc resize_func,
+                                    RAMResizeCleanupFunc cleanup_func,
+                                    void *opaque)
+{
+    VMStateRAMResizeHandler *rh;
+
+    assert(mr && resize_func);
+
+    QTAILQ_FOREACH(rh, &ram_resize_handlers, next) {
+        if (rh->mr == mr) {
+            /* only one resize handler per MemoryRegion */
+            assert(0);
+        }
+    }
+
+    rh = g_malloc0(sizeof(VMStateRAMResizeHandler));
+    rh->mr = mr;
+    rh->resize_func = resize_func;
+    rh->cleanup_func = cleanup_func;
+    rh->opaque = opaque;
+
+    QTAILQ_INSERT_TAIL(&ram_resize_handlers, rh, next);
+}
+
+void vmstate_unregister_ram_resizable_all(void)
+{
+    VMStateRAMResizeHandler *rh, *rh_next;
+
+    QTAILQ_FOREACH_SAFE(rh, &ram_resize_handlers, next, rh_next) {
+        if (rh->cleanup_func) {
+            rh->cleanup_func(rh->opaque);
+            QTAILQ_REMOVE(&ram_resize_handlers, rh, next);
+        }
+        g_free(rh);
+    }
+}
+
+const VMStateRAMResizeHandler *vmstate_find_ram_resize(const MemoryRegion *mr)
+{
+    VMStateRAMResizeHandler *rh;
+
+    QTAILQ_FOREACH(rh, &ram_resize_handlers, next) {
+        if (rh->mr == mr) {
+            return rh;
+        }
+    }
+
+    return NULL;
+}
+
+int vmstate_do_ram_resize(const VMStateRAMResizeHandler *rh, uint64_t size)
+{
+    int ret;
+
+    assert(rh);
+    ret = rh->resize_func(rh->mr, size, rh->opaque);
+    if (ret) {
+        fprintf(stderr, "Unable to resize ramblock \"%s\"",
+                memory_region_name(rh->mr));
+    }
+
+    return ret;
+}
-- 
1.7.9.5