[PATCH] hw/vhost-user-blk: fix ioeventfd add failed when start reenter

[Jie Wang]

During Virtio1.0 dev(start_on_kick) in vhost_user_blk_start process,
if spdk abnormal after vhost_dev_enable_notifiers, then vhost_user_blk_start 
will
goto vhost_dev_disable_notifiers and reenter vhost_user_blk_start, and
add ioeventfd again.

func call Process as follows:
vhost_user_blk_start(spdk abnormal after vhost_dev_enable_notifiers)
->vhost_dev_disable_notifiers
->virtio_bus_cleanup_host_notifier
->virtio_queue_host_notifier_read
->virtio_queue_notify_vq
->vhost_user_blk_handle_output
->vhost_user_blk_start
->vhost_dev_enable_notifiers

then kvm_mem_ioeventfd_add will failed with errno17(File exists) and
abort().

The GDB stack is as follows:
(gdb) bt
0  0x00007fca4264c81b in raise () from /usr/lib64/libc.so.6
1  0x00007fca4264db41 in abort () from /usr/lib64/libc.so.6
2  0x00007fca423ebe8b in kvm_mem_ioeventfd_add
3  0x00007fca4241c816 in address_space_add_del_ioeventfds
4  0x00007fca4241ddc6 in address_space_update_ioeventfds
5  0x00007fca424203d5 in memory_region_commit ()
6  0x00007fca424204e5 in memory_region_transaction_commit ()
7  0x00007fca42421861 in memory_region_add_eventfd
8  0x00007fca42917a4c in virtio_pci_ioeventfd_assign
9  0x00007fca41054178 in virtio_bus_set_host_notifier
10 0x00007fca41058729 in vhost_dev_enable_notifiers
11 0x00007fca40fdec1e in vhost_user_blk_start
12 0x00007fca40fdefa8 in vhost_user_blk_handle_output
13 0x00007fca4104e135 in virtio_queue_notify_vq
14 0x00007fca4104f192 in virtio_queue_host_notifier_read
15 0x00007fca41054054 in virtio_bus_cleanup_host_notifier
16 0x00007fca41058916 in vhost_dev_disable_notifiers
17 0x00007fca40fdede0 in vhost_user_blk_start
18 0x00007fca40fdefa8 in vhost_user_blk_handle_output
19 0x00007fca41050a6d in virtio_queue_notify
20 0x00007fca4241bbae in memory_region_write_accessor
21 0x00007fca4241ab1d in access_with_adjusted_size
22 0x00007fca4241e466 in memory_region_dispatch_write
23 0x00007fca4242da36 in flatview_write_continue
24 0x00007fca4242db75 in flatview_write
25 0x00007fca42430beb in address_space_write
26 0x00007fca42430c25 in address_space_rw
27 0x00007fca423e8ecc in kvm_handle_io
28 0x00007fca423ecb48 in kvm_cpu_exec
29 0x00007fca424279d5 in qemu_kvm_cpu_thread_fn
30 0x00007fca423c9480 in qemu_thread_start
31 0x00007fca4257ff3b in ?? () from /usr/lib64/libpthread.so.0
32 0x00007fca4270b550 in clone () from /usr/lib64/libc.so.6

Signed-off-by: Jie Wang <wangjie88@huawei.com>
---
 hw/block/vhost-user-blk.c          | 12 +++++++++++-
 include/hw/virtio/vhost-user-blk.h |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 1a42ae9187..2182769676 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -124,6 +124,13 @@ static int vhost_user_blk_start(VirtIODevice *vdev, Error 
**errp)
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     int i, ret;
 
+    if (vdev->start_on_kick) {
+        if (s->starting) {
+            return 0;
+        }
+        s->starting = true;
+    }
+
     if (!k->set_guest_notifiers) {
         error_setg(errp, "binding does not support guest notifiers");
         return -ENOSYS;
@@ -178,6 +185,8 @@ static int vhost_user_blk_start(VirtIODevice *vdev, Error 
**errp)
         vhost_virtqueue_mask(&s->dev, vdev, i, false);
     }
 
+    s->starting = false;
+
     return ret;
 
 err_guest_notifiers:
@@ -344,7 +353,7 @@ static int vhost_user_blk_connect(DeviceState *dev, Error 
**errp)
     }
 
     /* restore vhost state */
-    if (virtio_device_started(vdev, vdev->status)) {
+    if (s->starting || virtio_device_started(vdev, vdev->status)) {
         ret = vhost_user_blk_start(vdev, errp);
         if (ret < 0) {
             return ret;
@@ -500,6 +509,7 @@ static void vhost_user_blk_device_realize(DeviceState *dev, 
Error **errp)
                                         vhost_user_blk_handle_output);
     }
 
+    s->starting = false;
     s->inflight = g_new0(struct vhost_inflight, 1);
     s->vhost_vqs = g_new0(struct vhost_virtqueue, s->num_queues);
 
diff --git a/include/hw/virtio/vhost-user-blk.h 
b/include/hw/virtio/vhost-user-blk.h
index 7c91f15040..6e67f36962 100644
--- a/include/hw/virtio/vhost-user-blk.h
+++ b/include/hw/virtio/vhost-user-blk.h
@@ -51,6 +51,8 @@ struct VHostUserBlk {
     bool connected;
     /* vhost_user_blk_start/vhost_user_blk_stop */
     bool started_vu;
+
+    bool starting;
 };
 
 #endif
-- 
2.23.0