[PATCH RFC v4 11/16] virtio: disallow late feature changes for virtio-1

Cornelia Huck
2014-11-27T15:17:12Z

For virtio-1 devices, the driver must not attempt to set feature bits
after it set FEATURES_OK in the device status. Simply reject it in
that case.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
hw/virtio/virtio.c | 17 +++++++++++++++--
include/hw/virtio/virtio.h | 2 ++
2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 2c6bb91..8cdc0cb 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -982,7 +982,8 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
vmstate_save_state(f, &vmstate_virtio, vdev);
}

-int virtio_set_features(VirtIODevice *vdev, unsigned int index, uint32_t val)
+static int __virtio_set_features(VirtIODevice *vdev, unsigned int index,
+ uint32_t val)
{
BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
VirtioBusClass *vbusk = VIRTIO_BUS_GET_CLASS(qbus);
@@ -998,6 +999,18 @@ int virtio_set_features(VirtIODevice *vdev, unsigned int index, uint32_t val)
return bad ? -1 : 0;
}

+int virtio_set_features(VirtIODevice *vdev, unsigned int index, uint32_t val)
+{
+ /*
+ * The driver must not attempt to set features after feature negotiation
+ * has finished.
+ */
+ if (vdev->status & VIRTIO_CONFIG_S_FEATURES_OK) {
+ return -EINVAL;
+ }
+ return __virtio_set_features(vdev, index, val);
+}
+
int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
{
int i, ret;
@@ -1030,7 +1043,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
qemu_get_be32s(f, &features);

/* XXX features >= 32 */
- if (virtio_set_features(vdev, 0, features) < 0) {
+ if (__virtio_set_features(vdev, 0, features) < 0) {
supported_features = k->get_features(qbus->parent, 0);
error_report("Features 0x%x unsupported. Allowed features: 0x%x",
features, supported_features);
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index f840320..ec1be3b 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -32,6 +32,8 @@
#define VIRTIO_CONFIG_S_DRIVER 2
/* Driver has used its parts of the config, and is happy */
#define VIRTIO_CONFIG_S_DRIVER_OK 4
+/* Driver has finished configuring features */
+#define VIRTIO_CONFIG_S_FEATURES_OK 8
/* We've given up on this device. */
#define VIRTIO_CONFIG_S_FAILED 0x80

--
1.7.9.5