The TSO and MTU fallback paths reset the device before renegotiating
features. Reset clears all status bits, but these paths do not restore
ACKNOWLEDGE and DRIVER before setting FEATURES_OK and DRIVER_OK.
This violates the initialization sequence required by Virtio §3.1.1 [0].

We restore both bits after each fallback reset. This addresses one
incompatibility with the Cloud Hypervisor VMM, which requires the
complete initialization status before activating the device.

[0] https://docs.oasis-open.org/virtio/virtio/v1.4/cs01/virtio-v1.4-cs01.html

On-behalf-of: SAP leander.kohler@sap.com
Signed-off-by: Leander Kohler <leander.kohler@cyberus-technology.de>
---
 sys/dev/pv/if_vio.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git sys/dev/pv/if_vio.c sys/dev/pv/if_vio.c
index 8942b02857a..cb1dd8bf003 100644
--- sys/dev/pv/if_vio.c
+++ sys/dev/pv/if_vio.c
@@ -685,6 +685,8 @@ negotiate:
 		 */
 		want_tso = 0;
 		virtio_reset(vsc);
+		virtio_set_status(vsc, VIRTIO_CONFIG_DEVICE_STATUS_ACK);
+		virtio_set_status(vsc, VIRTIO_CONFIG_DEVICE_STATUS_DRIVER);
 		goto negotiate;
 	}
 
@@ -702,6 +704,8 @@ negotiate:
 			device_mtu = 0;
 			want_mtu = 0;
 			virtio_reset(vsc);
+			virtio_set_status(vsc, VIRTIO_CONFIG_DEVICE_STATUS_ACK);
+			virtio_set_status(vsc, VIRTIO_CONFIG_DEVICE_STATUS_DRIVER);
 			goto negotiate;
 		}
 	}