virtio: add endian-ambivalent support to VirtIODevice

Some CPU families can dynamically change their endianness. This means we
can have little endian ppc or big endian arm guests for example. This has
an impact on legacy virtio data structures since they are target endian.
We hence introduce a new property to track the endianness of each virtio
device. It is reasonnably assumed that endianness won't change while the
device is in use : we hence capture the device endianness when it gets
reset.

We migrate this property in a subsection, after the device descriptor. This
means the load code must not rely on it until it is restored. As a consequence,
the vring sanity checks had to be moved after the call to vmstate_load_state().
We enforce paranoia by poisoning the property at the begining of virtio_load().

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 9000ee2f50..a60104ca24 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -104,6 +104,12 @@ typedef struct VirtQueueElement
 #define VIRTIO_DEVICE(obj) \
         OBJECT_CHECK(VirtIODevice, (obj), TYPE_VIRTIO_DEVICE)
 
+enum virtio_device_endian {
+    VIRTIO_DEVICE_ENDIAN_UNKNOWN,
+    VIRTIO_DEVICE_ENDIAN_LITTLE,
+    VIRTIO_DEVICE_ENDIAN_BIG,
+};
+
 struct VirtIODevice
 {
     DeviceState parent_obj;
@@ -121,6 +127,7 @@ struct VirtIODevice
     bool vm_running;
     VMChangeStateEntry *vmstate;
     char *bus_name;
+    uint8_t device_endian;
 };
 
 typedef struct VirtioDeviceClass {
@@ -256,9 +263,9 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
 void virtio_queue_notify_vq(VirtQueue *vq);
 void virtio_irq(VirtQueue *vq);
 
-bool target_words_bigendian(void);
-static inline bool virtio_is_big_endian(void)
+static inline bool virtio_is_big_endian(VirtIODevice *vdev)
 {
-    return target_words_bigendian();
+    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
+    return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
 }
 #endif