s390x/virtio-ccw: add virtio set-revision call

Handle the virtio-ccw revision according to what the guest sets.
When revision 1 is selected, we have a virtio-1 standard device
with byteswapping for the virtio rings.

When a channel gets disabled, we have to revert to the legacy behavior
in case the next user of the device does not negotiate the revision 1
anymore (e.g. the boot firmware uses revision 1, but the operating
system only uses the legacy mode).

Note that revisions > 0 are still disabled.

[CH: assure memory accesses are always BE]
Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/hw/s390x/virtio-ccw.h b/hw/s390x/virtio-ccw.h
index d729263960..692ddd7318 100644
--- a/hw/s390x/virtio-ccw.h
+++ b/hw/s390x/virtio-ccw.h
@@ -41,6 +41,7 @@
 #define CCW_CMD_SET_CONF_IND 0x53
 #define CCW_CMD_READ_VQ_CONF 0x32
 #define CCW_CMD_SET_IND_ADAPTER 0x73
+#define CCW_CMD_SET_VIRTIO_REV 0x83
 
 #define TYPE_VIRTIO_CCW_DEVICE "virtio-ccw-device"
 #define VIRTIO_CCW_DEVICE(obj) \
@@ -86,6 +87,7 @@ struct VirtioCcwDevice {
     DeviceState parent_obj;
     SubchDev *sch;
     char *bus_id;
+    int revision;
     VirtioBusState bus;
     bool ioeventfd_started;
     bool ioeventfd_disabled;
@@ -99,6 +101,12 @@ struct VirtioCcwDevice {
     uint64_t ind_bit;
 };
 
+/* The maximum virtio revision we support. */
+static inline int virtio_ccw_rev_max(VirtIODevice *vdev)
+{
+    return 0;
+}
+
 /* virtual css bus type */
 typedef struct VirtualCssBus {
     BusState parent_obj;