[Devel] [PATCH RHEL9 COMMIT] vhost/vsock: add VHOST_RESET_OWNER ioctl

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-427.44.1.vz9.80.x-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh9-5.14.0-427.44.1.vz9.80.8
------>
commit ad35221ad13416f3eb981d5f2c33312dd88fa692
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date:   Tue Jan 28 18:48:01 2025 +0800

    vhost/vsock: add VHOST_RESET_OWNER ioctl
    
    We plan to use it to be able to execute new qemu version and take over
    the contol over /dev/vhost-vsock file by reseting the owner and setting
    a new one. We expect not to lose any AF_VSOCK connection while this
    happens.
    
    https://virtuozzo.atlassian.net/browse/VSTOR-98105
    Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
    
    Feature: vhost-vsock: VHOST_RESET_OWNER ioctl
---
 drivers/vhost/vsock.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index ca6a95204b4a..3654fa0fd584 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -839,6 +839,34 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 	return -EFAULT;
 }
 
+static int vhost_vsock_reset_owner(struct vhost_vsock *vsock)
+{
+	struct vhost_iotlb *umem;
+	long err;
+	size_t i;
+
+	mutex_lock(&vsock->dev.mutex);
+	err = vhost_dev_check_owner(&vsock->dev);
+	if (err)
+		goto done;
+	umem = vhost_dev_reset_owner_prepare();
+	if (!umem) {
+		err = -ENOMEM;
+		goto done;
+	}
+	/* Follows vhost_vsock_dev_release closely except for guest_cid drop */
+	vsock_for_each_connected_socket(&vhost_transport.transport,
+					vhost_vsock_reset_orphans);
+	vhost_vsock_drop_backends(vsock);
+	vhost_vsock_flush(vsock);
+	vhost_dev_stop(&vsock->dev);
+	virtio_vsock_skb_queue_purge(&vsock->send_pkt_queue);
+	vhost_dev_reset_owner(&vsock->dev, umem);
+done:
+	mutex_unlock(&vsock->dev.mutex);
+	return err;
+}
+
 static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
 				  unsigned long arg)
 {
@@ -882,6 +910,8 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
 			return -EOPNOTSUPP;
 		vhost_set_backend_features(&vsock->dev, features);
 		return 0;
+	case VHOST_RESET_OWNER:
+		return vhost_vsock_reset_owner(vsock);
 	default:
 		mutex_lock(&vsock->dev.mutex);
 		r = vhost_dev_ioctl(&vsock->dev, ioctl, argp);