Revert "vhost-blk: set features before setting inflight feature"

This reverts commit adb29c02.

The commit broke -device vhost-user-blk-pci because the
vhost_dev_prepare_inflight() function it introduced segfaults in
vhost_dev_set_features() when attempting to access struct vhost_dev's
vdev pointer before it has been assigned.

To reproduce the segfault simply launch a vhost-user-blk device with the
contrib vhost-user-blk device backend:

  $ build/contrib/vhost-user-blk/vhost-user-blk -s /tmp/vhost-user-blk.sock -r -b /var/tmp/foo.img
  $ build/qemu-system-x86_64 \
        -device vhost-user-blk-pci,id=drv0,chardev=char1,addr=4.0 \
        -object memory-backend-memfd,id=mem,size=1G,share=on \
        -M memory-backend=mem,accel=kvm \
        -chardev socket,id=char1,path=/tmp/vhost-user-blk.sock
  Segmentation fault (core dumped)

Cc: Jin Yu <jin.yu@intel.com>
Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201102165709.232180-1-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/block/vhost-user-blk.c

@@ -131,12 +131,6 @@ static int vhost_user_blk_start(VirtIODevice *vdev)
 
     s->dev.acked_features = vdev->guest_features;
 
-    ret = vhost_dev_prepare_inflight(&s->dev);
-    if (ret < 0) {
-        error_report("Error set inflight format: %d", -ret);
-        goto err_guest_notifiers;
-    }
-
     if (!s->inflight->addr) {
         ret = vhost_dev_get_inflight(&s->dev, s->queue_size, s->inflight);
         if (ret < 0) {

hw/virtio/vhost.c

@@ -1645,24 +1645,6 @@ int vhost_dev_load_inflight(struct vhost_inflight *inflight, QEMUFile *f)
     return 0;
 }
 
-int vhost_dev_prepare_inflight(struct vhost_dev *hdev)
-{
-    int r;
- 
-    if (hdev->vhost_ops->vhost_get_inflight_fd == NULL ||
-        hdev->vhost_ops->vhost_set_inflight_fd == NULL) {
-        return 0;
-    }
- 
-    r = vhost_dev_set_features(hdev, hdev->log_enabled);
-    if (r < 0) {
-        VHOST_OPS_DEBUG("vhost_dev_prepare_inflight failed");
-        return r;
-    }
-
-    return 0;
-}
-
 int vhost_dev_set_inflight(struct vhost_dev *dev,
                            struct vhost_inflight *inflight)
 {

include/hw/virtio/vhost.h

@@ -141,7 +141,6 @@ void vhost_dev_reset_inflight(struct vhost_inflight *inflight);
 void vhost_dev_free_inflight(struct vhost_inflight *inflight);
 void vhost_dev_save_inflight(struct vhost_inflight *inflight, QEMUFile *f);
 int vhost_dev_load_inflight(struct vhost_inflight *inflight, QEMUFile *f);
-int vhost_dev_prepare_inflight(struct vhost_dev *hdev);
 int vhost_dev_set_inflight(struct vhost_dev *dev,
                            struct vhost_inflight *inflight);
 int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,