vhost: init used ring after backend was set

Move the used ring initialization after backend was set. This
makes it possible to disable the backend and tweak the used ring,
then restart. This will also make it possible to log the used ring
write correctly.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index f0fd52cdfadc05b6fcd57b9efff0eddee4173d2a..70ac60437d174411f891f20f8b477b20b74e8e8e 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -703,6 +703,10 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
                vhost_net_disable_vq(n, vq);
                rcu_assign_pointer(vq->private_data, sock);
                vhost_net_enable_vq(n, vq);
+
+               r = vhost_init_used(vq);
+               if (r)
+                       goto err_vq;
        }
 
        mutex_unlock(&vq->mutex);

diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 734e1d74ad805a1547ed867dd8363f09bcd9e2f8..fc9a1d75281f33d57be305b3c724195c578334de 100644 (file)
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -195,8 +195,13 @@ static long vhost_test_run(struct vhost_test *n, int test)
                                                    lockdep_is_held(&vq->mutex));
                rcu_assign_pointer(vq->private_data, priv);
 
+               r = vhost_init_used(&n->vqs[index]);
+
                mutex_unlock(&vq->mutex);
 
+               if (r)
+                       goto err;
+
                if (oldpriv) {
                        vhost_test_flush_vq(n, index);
                }

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5ef2f62becf4b94c69082b4dc1b1a2f6eacd84ac..9a108038fe527393f6ac2b04a2104916b1518290 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -629,15 +629,17 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
        return 0;
 }
 
-static int init_used(struct vhost_virtqueue *vq,
-                    struct vring_used __user *used)
+int vhost_init_used(struct vhost_virtqueue *vq)
 {
-       int r = put_user(vq->used_flags, &used->flags);
+       int r;
+       if (!vq->private_data)
+               return 0;
 
+       r = put_user(vq->used_flags, &vq->used->flags);
        if (r)
                return r;
        vq->signalled_used_valid = false;
-       return get_user(vq->last_used_idx, &used->idx);
+       return get_user(vq->last_used_idx, &vq->used->idx);
 }
 
 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
@@ -752,10 +754,6 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                        }
                }
 
-               r = init_used(vq, (struct vring_used __user *)(unsigned long)
-                             a.used_user_addr);
-               if (r)
-                       break;
                vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
                vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
                vq->avail = (void __user *)(unsigned long)a.avail_user_addr;

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 1544b782529b5803730ac6e447ac698caa7c7239..14c9abf0d80025fd863460c1bd935d5b49f88c26 100644 (file)
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -174,6 +174,7 @@ int vhost_get_vq_desc(struct vhost_dev *, struct vhost_virtqueue *,
                      struct vhost_log *log, unsigned int *log_num);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
+int vhost_init_used(struct vhost_virtqueue *);
 int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
 int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
                     unsigned count);