virtio-scsi-test: add missing feature negotiation

VIRTIO Device Initialization requires feature negotiation.  Currently
virtio-scsi-test.c is non-compliant.

libqos tests acknowledge all feature bits advertised by the device,
except VIRTIO_F_BAD_FEATURE (which devices use to detect broken
drivers!) and VIRTIO_RING_F_EVENT_IDX (which is not implemented in
libqos and accepting it would break notifications).

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20191023100425.12168-5-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Thomas Huth" <thuth@redhat.com>

tests/virtio-scsi-test.c

@@ -123,10 +123,16 @@ static QVirtioSCSIQueues *qvirtio_scsi_init(QVirtioDevice *dev)
     QVirtioSCSIQueues *vs;
     const uint8_t test_unit_ready_cdb[VIRTIO_SCSI_CDB_SIZE] = {};
     struct virtio_scsi_cmd_resp resp;
+    uint64_t features;
     int i;
 
     vs = g_new0(QVirtioSCSIQueues, 1);
     vs->dev = dev;
+
+    features = qvirtio_get_features(dev);
+    features &= ~(QVIRTIO_F_BAD_FEATURE | (1ull << VIRTIO_RING_F_EVENT_IDX));
+    qvirtio_set_features(dev, features);
+
     vs->num_queues = qvirtio_config_readl(dev, 0);
 
     g_assert_cmpint(vs->num_queues, <, MAX_NUM_QUEUES);
@@ -135,6 +141,8 @@ static QVirtioSCSIQueues *qvirtio_scsi_init(QVirtioDevice *dev)
         vs->vq[i] = qvirtqueue_setup(dev, alloc, i);
     }
 
+    qvirtio_set_driver_ok(dev);
+
     /* Clear the POWER ON OCCURRED unit attention */
     g_assert_cmpint(virtio_scsi_do_command(vs, test_unit_ready_cdb,
                                            NULL, 0, NULL, 0, &resp),