[PATCH 66/77] virtio: verify that legacy support is not accidentally on

[Michael Roth]

From: Cornelia Huck <cohuck@redhat.com>

If a virtio device does not have legacy support, make sure that
it is actually off, and bail out if not.

For virtio-pci, this means that any device without legacy support
that has been specified to modern-only (or that has been forced
to it) will work.

For virtio-ccw, this duplicates the check that is currently done
prior to realization for any device that explicitly specified no
support for legacy.

This catches devices that have not been fenced properly.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200707105446.677966-3-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 9b3a35ec8236933ab958a4c3ad883163f1ca66e7)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 hw/s390x/virtio-ccw.c  | 6 ++++++
 hw/virtio/virtio-pci.c | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 64f928fc7d..c069719429 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -1119,6 +1119,12 @@ static void virtio_ccw_device_plugged(DeviceState *d, 
Error **errp)
         dev->max_rev = 0;
     }
 
+    if (!virtio_ccw_rev_max(dev) && !virtio_legacy_allowed(vdev)) {
+        error_setg(errp, "Invalid value of property max_rev "
+                   "(is %d expected >= 1)", virtio_ccw_rev_max(dev));
+        return;
+    }
+
     if (virtio_get_num_queues(vdev) > VIRTIO_QUEUE_MAX) {
         error_setg(errp, "The number of virtqueues %d "
                    "exceeds virtio limit %d", n,
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 4cb784389c..2ca266e1cb 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1565,6 +1565,10 @@ static void virtio_pci_device_plugged(DeviceState *d, 
Error **errp)
     }
 
     if (legacy) {
+        if (!virtio_legacy_allowed(vdev)) {
+            error_setg(errp, "device is modern-only, use disable-legacy=on");
+            return;
+        }
         if (virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) {
             error_setg(errp, "VIRTIO_F_IOMMU_PLATFORM was supported by"
                        " neither legacy nor transitional device");
-- 
2.17.1