I run "dpdk-vdpa" and "qemur-L2" in "qemu-L1".
In a nested virtualization environment, "qemu-L2" vhost-user socket sends a "VHOST_USER_IOTLB_MSG" message to "dpdk-vdpa" and blocks waiting for "dpdk-vdpa" to process the message. If "dpdk-vdpa" doesn't complete the processing of the "VHOST_USER_IOTLB_MSG" message and sends a message that needs to be replied in another thread, such as "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG", "dpdk-vdpa" will also block and wait for "qemu-L2" to process this message. However, "qemu-L2" vhost-user's socket is blocking while waiting for a reply from "dpdk-vdpa" after processing the message "VHOSTr_USER_IOTLB_MSG", and "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG" will not be processed. In this case, both "dpdk-vdpa" and "qemu-L2" are blocked on the vhost read, resulting in a deadlock. You can modify "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG" or "VHOST_USER_IOTLB_MSG" to "no need reply" to fix this issue. There are too many messages in dpdk that are similar to "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG", and I would prefer the latter. Fixes: 24e34754eb78 ("vhost-user: factor out msg head and payload") Signed-off-by: Hao Chen <ch...@yusur.tech> --- hw/virtio/vhost-user.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index f214df804b..02caa94b6c 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -2371,20 +2371,14 @@ static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu) static int vhost_user_send_device_iotlb_msg(struct vhost_dev *dev, struct vhost_iotlb_msg *imsg) { - int ret; VhostUserMsg msg = { .hdr.request = VHOST_USER_IOTLB_MSG, .hdr.size = sizeof(msg.payload.iotlb), - .hdr.flags = VHOST_USER_VERSION | VHOST_USER_NEED_REPLY_MASK, + .hdr.flags = VHOST_USER_VERSION, .payload.iotlb = *imsg, }; - ret = vhost_user_write(dev, &msg, NULL, 0); - if (ret < 0) { - return ret; - } - - return process_message_reply(dev, &msg); + return vhost_user_write(dev, &msg, NULL, 0); } -- 2.27.0