virtio: hide legacy features from modern guests

NOTIFY_ON_EMPTY, ANY_LAYOUT and BAD are only valid on the legacy
interface.

Hide them from modern guests.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 283401a..db8f27c 100644 (file)
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1095,7 +1095,8 @@ static uint64_t virtio_pci_common_read(void *opaque, hwaddr addr,
         break;
     case VIRTIO_PCI_COMMON_DF:
         if (proxy->dfselect <= 1) {
-            val = vdev->host_features >> (32 * proxy->dfselect);
+            val = (vdev->host_features & ~VIRTIO_LEGACY_FEATURES) >>
+                (32 * proxy->dfselect);
         }
         break;
     case VIRTIO_PCI_COMMON_GFSELECT:

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 473fb75..0634c15 100644 (file)
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -25,6 +25,10 @@
 /* A guest should never accept this.  It implies negotiation is broken. */
 #define VIRTIO_F_BAD_FEATURE           30
 
+#define VIRTIO_LEGACY_FEATURES ((0x1ULL << VIRTIO_F_BAD_FEATURE) | \
+                                (0x1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) | \
+                                (0x1ULL << VIRTIO_F_ANY_LAYOUT))
+
 struct VirtQueue;
 
 static inline hwaddr vring_align(hwaddr addr,