[Qemu-devel] [PATCH v2 1/2] virtio: Add function to check whether backend supports VIRTIO_1

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch adds virtio_test_backend_virtio_1() function to
check whether backend supports VIRTIO_F_VERSION_1 before the
negociation takes place.

Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 hw/virtio/virtio.c         | 13 +++++++++++++
 include/hw/virtio/virtio.h |  1 +
 2 files changed, 14 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 74c085c..8b30b69 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1481,6 +1481,19 @@ void virtio_vmstate_save(QEMUFile *f, void *opaque, size_t size)
     virtio_save(VIRTIO_DEVICE(opaque), f);
 }
 
+bool virtio_test_backend_virtio_1(VirtIODevice *vdev, Error **errp)
+{
+    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
+    uint64_t feature;
+
+    virtio_add_feature(&feature, VIRTIO_F_VERSION_1);
+
+    assert(k->get_features != NULL);
+    feature = k->get_features(vdev, feature, errp);
+
+    return virtio_has_feature(feature, VIRTIO_F_VERSION_1);
+}
+
 static int virtio_set_features_nocheck(VirtIODevice *vdev, uint64_t val)
 {
     VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index d2490c1..3a31754 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -235,6 +235,7 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val);
 void virtio_reset(void *opaque);
 void virtio_update_irq(VirtIODevice *vdev);
 int virtio_set_features(VirtIODevice *vdev, uint64_t val);
+bool virtio_test_backend_virtio_1(VirtIODevice *vdev, Error **errp);
 
 /* Base devices.  */
 typedef struct VirtIOBlkConf VirtIOBlkConf;
-- 
2.7.4