vdpa/mlx5: Fix release of uninitialized resources on error path

The commit in the fixes tag made sure that mlx5_vdpa_free()
is the single entrypoint for removing the vdpa device resources
added in mlx5_vdpa_dev_add(), even in the cleanup path of
mlx5_vdpa_dev_add().

This means that all functions from mlx5_vdpa_free() should be able to
handle uninitialized resources. This was not the case though:
mlx5_vdpa_destroy_mr_resources() and mlx5_cmd_cleanup_async_ctx()
were not able to do so. This caused the splat below when adding
a vdpa device without a MAC address.

This patch fixes these remaining issues:

- Makes mlx5_vdpa_destroy_mr_resources() return early if called on
  uninitialized resources.

- Moves mlx5_cmd_init_async_ctx() early on during device addition
  because it can't fail. This means that mlx5_cmd_cleanup_async_ctx()
  also can't fail. To mirror this, move the call site of
  mlx5_cmd_cleanup_async_ctx() in mlx5_vdpa_free().

An additional comment was added in mlx5_vdpa_free() to document
the expectations of functions called from this context.

Splat:

  mlx5_core 0000:b5:03.2: mlx5_vdpa_dev_add:3950:(pid 2306) warning: No mac address provisioned?
  ------------[ cut here ]------------
  WARNING: CPU: 13 PID: 2306 at kernel/workqueue.c:4207 __flush_work+0x9a/0xb0
  [...]
  Call Trace:
   <TASK>
   ? __try_to_del_timer_sync+0x61/0x90
   ? __timer_delete_sync+0x2b/0x40
   mlx5_vdpa_destroy_mr_resources+0x1c/0x40 [mlx5_vdpa]
   mlx5_vdpa_free+0x45/0x160 [mlx5_vdpa]
   vdpa_release_dev+0x1e/0x50 [vdpa]
   device_release+0x31/0x90
   kobject_cleanup+0x37/0x130
   mlx5_vdpa_dev_add+0x327/0x890 [mlx5_vdpa]
   vdpa_nl_cmd_dev_add_set_doit+0x2c1/0x4d0 [vdpa]
   genl_family_rcv_msg_doit+0xd8/0x130
   genl_family_rcv_msg+0x14b/0x220
   ? __pfx_vdpa_nl_cmd_dev_add_set_doit+0x10/0x10 [vdpa]
   genl_rcv_msg+0x47/0xa0
   ? __pfx_genl_rcv_msg+0x10/0x10
   netlink_rcv_skb+0x53/0x100
   genl_rcv+0x24/0x40
   netlink_unicast+0x27b/0x3b0
   netlink_sendmsg+0x1f7/0x430
   __sys_sendto+0x1fa/0x210
   ? ___pte_offset_map+0x17/0x160
   ? next_uptodate_folio+0x85/0x2b0
   ? percpu_counter_add_batch+0x51/0x90
   ? filemap_map_pages+0x515/0x660
   __x64_sys_sendto+0x20/0x30
   do_syscall_64+0x7b/0x2c0
   ? do_read_fault+0x108/0x220
   ? do_pte_missing+0x14a/0x3e0
   ? __handle_mm_fault+0x321/0x730
   ? count_memcg_events+0x13f/0x180
   ? handle_mm_fault+0x1fb/0x2d0
   ? do_user_addr_fault+0x20c/0x700
   ? syscall_exit_work+0x104/0x140
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
  RIP: 0033:0x7f0c25b0feca
  [...]
  ---[ end trace 0000000000000000 ]---

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Fixes: 83e445e ("vdpa/mlx5: Fix error path during device add")
Reported-by: Wenli Quan <wquan@redhat.com>
Closes: https://lore.kernel.org/virtualization/CADZSLS0r78HhZAStBaN1evCSoPqRJU95Lt8AqZNJ6+wwYQ6vPQ@mail.gmail.com/
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Message-Id: <20250708120424.2363354-2-dtatulea@nvidia.com>
Tested-by: Wenli Quan <wquan@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: dtatulea

drivers/vdpa/mlx5/core/mr.c

@@ -908,6 +908,9 @@ void mlx5_vdpa_destroy_mr_resources(struct mlx5_vdpa_dev *mvdev)
 {
 	struct mlx5_vdpa_mr_resources *mres = &mvdev->mres;
 
+	if (!mres->wq_gc)
+		return;
+
 	atomic_set(&mres->shutdown, 1);
 
 	flush_delayed_work(&mres->gc_dwork_ent);

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -3432,15 +3432,17 @@ static void mlx5_vdpa_free(struct vdpa_device *vdev)
 
 	ndev = to_mlx5_vdpa_ndev(mvdev);
 
+	/* Functions called here should be able to work with
+	 * uninitialized resources.
+	 */
 	free_fixed_resources(ndev);
 	mlx5_vdpa_clean_mrs(mvdev);
 	mlx5_vdpa_destroy_mr_resources(&ndev->mvdev);
-	mlx5_cmd_cleanup_async_ctx(&mvdev->async_ctx);
-
 	if (!is_zero_ether_addr(ndev->config.mac)) {
 		pfmdev = pci_get_drvdata(pci_physfn(mvdev->mdev->pdev));
 		mlx5_mpfs_del_mac(pfmdev, ndev->config.mac);
 	}
+	mlx5_cmd_cleanup_async_ctx(&mvdev->async_ctx);
 	mlx5_vdpa_free_resources(&ndev->mvdev);
 	free_irqs(ndev);
 	kfree(ndev->event_cbs);
@@ -3888,6 +3890,8 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
 	mvdev->actual_features =
 			(device_features & BIT_ULL(VIRTIO_F_VERSION_1));
 
+	mlx5_cmd_init_async_ctx(mdev, &mvdev->async_ctx);
+
 	ndev->vqs = kcalloc(max_vqs, sizeof(*ndev->vqs), GFP_KERNEL);
 	ndev->event_cbs = kcalloc(max_vqs + 1, sizeof(*ndev->event_cbs), GFP_KERNEL);
 	if (!ndev->vqs || !ndev->event_cbs) {
@@ -3960,8 +3964,6 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
 		ndev->rqt_size = 1;
 	}
 
-	mlx5_cmd_init_async_ctx(mdev, &mvdev->async_ctx);
-
 	ndev->mvdev.mlx_features = device_features;
 	mvdev->vdev.dma_dev = &mdev->pdev->dev;
 	err = mlx5_vdpa_alloc_resources(&ndev->mvdev);