virtio: add and use virtio_set_features

vdev->guest_features is not masking features that are not supported by
the guest.  Fix this by introducing a common wrapper to be used by all
virtio bus implementations.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 18 insertions, 6 deletions

diff --git a/hw/virtio.c b/hw/virtio.c
index 7011b5b398..81ecc40b31 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -763,12 +763,25 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
     }
 }
 
+int virtio_set_features(VirtIODevice *vdev, uint32_t val)
+{
+    uint32_t supported_features =
+        vdev->binding->get_features(vdev->binding_opaque);
+    bool bad = (val & ~supported_features) != 0;
+
+    val &= supported_features;
+    if (vdev->set_features) {
+        vdev->set_features(vdev, val);
+    }
+    vdev->guest_features = val;
+    return bad ? -1 : 0;
+}
+
 int virtio_load(VirtIODevice *vdev, QEMUFile *f)
 {
     int num, i, ret;
     uint32_t features;
-    uint32_t supported_features =
-        vdev->binding->get_features(vdev->binding_opaque);
+    uint32_t supported_features;
 
     if (vdev->binding->load_config) {
         ret = vdev->binding->load_config(vdev->binding_opaque, f);
@@ -780,14 +793,13 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f)
     qemu_get_8s(f, &vdev->isr);
     qemu_get_be16s(f, &vdev->queue_sel);
     qemu_get_be32s(f, &features);
-    if (features & ~supported_features) {
+
+    if (virtio_set_features(vdev, features) < 0) {
+        supported_features = vdev->binding->get_features(vdev->binding_opaque);
         error_report("Features 0x%x unsupported. Allowed features: 0x%x",
                      features, supported_features);
         return -1;
     }
-    if (vdev->set_features)
-        vdev->set_features(vdev, features);
-    vdev->guest_features = features;
     vdev->config_len = qemu_get_be32(f);
     qemu_get_buffer(f, vdev->config, vdev->config_len);