[RFC,10/15] virtio-mem: Set the RamDiscardManager for the RAM memory region earlier

Commit Message

David Hildenbrand Oct. 13, 2021, 10:33 a.m. UTC

Let's set the RamDiscardManager earlier, logically before we expose the
RAM memory region to the system. This is a preparation for further changes
and is logically cleaner: before we expose the RAM memory region to
migration code, make sure we have the RamDiscardManager setup.

Signed-off-by: David Hildenbrand <[e-mail]>
---
 hw/virtio/virtio-mem.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

Patch

diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index d5a578142b..b2ad27ed7f 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -773,16 +773,17 @@  static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
                 sizeof(struct virtio_mem_config));
     vmem->vq = virtio_add_queue(vdev, 128, virtio_mem_handle_request);
 
-    host_memory_backend_set_mapped(vmem->memdev, true);
-    vmstate_register_ram(&vmem->memdev->mr, DEVICE(vmem));
-    qemu_register_reset(virtio_mem_system_reset, vmem);
-
     /*
-     * Set ourselves as RamDiscardManager before the plug handler maps the
-     * memory region and exposes it via an address space.
+     * Set ourselves as RamDiscardManager before we expose the memory region
+     * to the system (e.g., marking the RAMBlock migratable, mapping the
+     * region).
      */
     memory_region_set_ram_discard_manager(&vmem->memdev->mr,
                                           RAM_DISCARD_MANAGER(vmem));
+
+    host_memory_backend_set_mapped(vmem->memdev, true);
+    vmstate_register_ram(&vmem->memdev->mr, DEVICE(vmem));
+    qemu_register_reset(virtio_mem_system_reset, vmem);
 }
 
 static void virtio_mem_device_unrealize(DeviceState *dev)
@@ -790,14 +791,10 @@  static void virtio_mem_device_unrealize(DeviceState *dev)
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VirtIOMEM *vmem = VIRTIO_MEM(dev);
 
-    /*
-     * The unplug handler unmapped the memory region, it cannot be
-     * found via an address space anymore. Unset ourselves.
-     */
-    memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL);
     qemu_unregister_reset(virtio_mem_system_reset, vmem);
     vmstate_unregister_ram(&vmem->memdev->mr, DEVICE(vmem));
     host_memory_backend_set_mapped(vmem->memdev, false);
+    memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL);
     virtio_del_queue(vdev, 0);
     virtio_cleanup(vdev);
     g_free(vmem->bitmap);