[PATCH 65/77] virtio: list legacy-capable devices

[Michael Roth]

From: Cornelia Huck <cohuck@redhat.com>

Several types of virtio devices had already been around before the
virtio standard was specified. These devices support virtio in legacy
(and transitional) mode.

Devices that have been added in the virtio standard are considered
non-transitional (i.e. with no support for legacy virtio).

Provide a helper function so virtio transports can figure that out
easily.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200707105446.677966-2-cohuck@redhat.com>
Cc: qemu-stable@nongnu.org
Acked-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 7c78bdd7a3d0086179331f10d1f6f8cdac34731a)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 hw/virtio/virtio.c         | 25 +++++++++++++++++++++++++
 include/hw/virtio/virtio.h |  2 ++
 2 files changed, 27 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index b6c8ef5bc0..398fd4a305 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -27,6 +27,7 @@
 #include "hw/virtio/virtio-access.h"
 #include "sysemu/dma.h"
 #include "sysemu/runstate.h"
+#include "standard-headers/linux/virtio_ids.h"
 
 /*
  * The alignment to use between consumer and producer parts of vring.
@@ -3278,6 +3279,30 @@ void virtio_init(VirtIODevice *vdev, const char *name,
     vdev->use_guest_notifier_mask = true;
 }
 
+/*
+ * Only devices that have already been around prior to defining the virtio
+ * standard support legacy mode; this includes devices not specified in the
+ * standard. All newer devices conform to the virtio standard only.
+ */
+bool virtio_legacy_allowed(VirtIODevice *vdev)
+{
+    switch (vdev->device_id) {
+    case VIRTIO_ID_NET:
+    case VIRTIO_ID_BLOCK:
+    case VIRTIO_ID_CONSOLE:
+    case VIRTIO_ID_RNG:
+    case VIRTIO_ID_BALLOON:
+    case VIRTIO_ID_RPMSG:
+    case VIRTIO_ID_SCSI:
+    case VIRTIO_ID_9P:
+    case VIRTIO_ID_RPROC_SERIAL:
+    case VIRTIO_ID_CAIF:
+        return true;
+    default:
+        return false;
+    }
+}
+
 hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)
 {
     return vdev->vq[n].vring.desc;
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index b69d517496..198ffc7626 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -396,4 +396,6 @@ static inline bool virtio_device_disabled(VirtIODevice 
*vdev)
     return unlikely(vdev->disabled || vdev->broken);
 }
 
+bool virtio_legacy_allowed(VirtIODevice *vdev);
+
 #endif
-- 
2.17.1