Let's prepare for a new virtio-mem kdump mode in which we don't actually
hot(un)plug any memory but only observe the state of device blocks.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/virtio/virtio_mem.c | 87 +++++++++++++++++++------------------
 1 file changed, 45 insertions(+), 42 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 2ba7e8d6ba8d..1be3ee7f684d 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -260,6 +260,8 @@ static void virtio_mem_fake_offline_going_offline(unsigned long pfn,
 static void virtio_mem_fake_offline_cancel_offline(unsigned long pfn,
 						   unsigned long nr_pages);
 static void virtio_mem_retry(struct virtio_mem *vm);
+static int virtio_mem_create_resource(struct virtio_mem *vm);
+static void virtio_mem_delete_resource(struct virtio_mem *vm);
 
 /*
  * Register a virtio-mem device so it will be considered for the online_page
@@ -2395,7 +2397,8 @@ static int virtio_mem_init_vq(struct virtio_mem *vm)
 static int virtio_mem_init_hotplug(struct virtio_mem *vm)
 {
 	const struct range pluggable_range = mhp_get_pluggable_range(true);
-	uint64_t sb_size, addr;
+	uint64_t unit_pages, sb_size, addr;
+	int rc;
 
 	/* bad device setup - warn only */
 	if (!IS_ALIGNED(vm->addr, memory_block_size_bytes()))
@@ -2474,7 +2477,48 @@ static int virtio_mem_init_hotplug(struct virtio_mem *vm)
 		dev_info(&vm->vdev->dev, "big block size: 0x%llx",
 			 (unsigned long long)vm->bbm.bb_size);
 
+	/* create the parent resource for all memory */
+	rc = virtio_mem_create_resource(vm);
+	if (rc)
+		return rc;
+
+	/* use a single dynamic memory group to cover the whole memory device */
+	if (vm->in_sbm)
+		unit_pages = PHYS_PFN(memory_block_size_bytes());
+	else
+		unit_pages = PHYS_PFN(vm->bbm.bb_size);
+	rc = memory_group_register_dynamic(vm->nid, unit_pages);
+	if (rc < 0)
+		goto out_del_resource;
+	vm->mgid = rc;
+
+	/*
+	 * If we still have memory plugged, we have to unplug all memory first.
+	 * Registering our parent resource makes sure that this memory isn't
+	 * actually in use (e.g., trying to reload the driver).
+	 */
+	if (vm->plugged_size) {
+		vm->unplug_all_required = true;
+		dev_info(&vm->vdev->dev, "unplugging all memory is required\n");
+	}
+
+	/* register callbacks */
+	vm->memory_notifier.notifier_call = virtio_mem_memory_notifier_cb;
+	rc = register_memory_notifier(&vm->memory_notifier);
+	if (rc)
+		goto out_unreg_group;
+	rc = register_virtio_mem_device(vm);
+	if (rc)
+		goto out_unreg_mem;
+
 	return 0;
+out_unreg_mem:
+	unregister_memory_notifier(&vm->memory_notifier);
+out_unreg_group:
+	memory_group_unregister(vm->mgid);
+out_del_resource:
+	virtio_mem_delete_resource(vm);
+	return rc;
 }
 
 static int virtio_mem_init(struct virtio_mem *vm)
@@ -2578,7 +2622,6 @@ static bool virtio_mem_has_memory_added(struct virtio_mem *vm)
 static int virtio_mem_probe(struct virtio_device *vdev)
 {
 	struct virtio_mem *vm;
-	uint64_t unit_pages;
 	int rc;
 
 	BUILD_BUG_ON(sizeof(struct virtio_mem_req) != 24);
@@ -2608,40 +2651,6 @@ static int virtio_mem_probe(struct virtio_device *vdev)
 	if (rc)
 		goto out_del_vq;
 
-	/* create the parent resource for all memory */
-	rc = virtio_mem_create_resource(vm);
-	if (rc)
-		goto out_del_vq;
-
-	/* use a single dynamic memory group to cover the whole memory device */
-	if (vm->in_sbm)
-		unit_pages = PHYS_PFN(memory_block_size_bytes());
-	else
-		unit_pages = PHYS_PFN(vm->bbm.bb_size);
-	rc = memory_group_register_dynamic(vm->nid, unit_pages);
-	if (rc < 0)
-		goto out_del_resource;
-	vm->mgid = rc;
-
-	/*
-	 * If we still have memory plugged, we have to unplug all memory first.
-	 * Registering our parent resource makes sure that this memory isn't
-	 * actually in use (e.g., trying to reload the driver).
-	 */
-	if (vm->plugged_size) {
-		vm->unplug_all_required = true;
-		dev_info(&vm->vdev->dev, "unplugging all memory is required\n");
-	}
-
-	/* register callbacks */
-	vm->memory_notifier.notifier_call = virtio_mem_memory_notifier_cb;
-	rc = register_memory_notifier(&vm->memory_notifier);
-	if (rc)
-		goto out_unreg_group;
-	rc = register_virtio_mem_device(vm);
-	if (rc)
-		goto out_unreg_mem;
-
 	virtio_device_ready(vdev);
 
 	/* trigger a config update to start processing the requested_size */
@@ -2649,12 +2658,6 @@ static int virtio_mem_probe(struct virtio_device *vdev)
 	queue_work(system_freezable_wq, &vm->wq);
 
 	return 0;
-out_unreg_mem:
-	unregister_memory_notifier(&vm->memory_notifier);
-out_unreg_group:
-	memory_group_unregister(vm->mgid);
-out_del_resource:
-	virtio_mem_delete_resource(vm);
 out_del_vq:
 	vdev->config->del_vqs(vdev);
 out_free_vm:
-- 
2.31.1