virtio_balloon: disable VIOMMU support

virtio balloon bypasses the DMA API entirely so does not support the
VIOMMU right now.  It's not clear we need that support, for now let's
just make sure we don't pretend to support it.

Cc: stable@vger.kernel.org
Cc: Wei Wang <wei.w.wang@intel.com>
Fixes: 1a937693993f ("virtio: new feature to detect IOMMU device quirk")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 408c174ef0d5c076dc2f51da612b8e0f3dfa8269..22caf808bfaba97e45662de0f4150632bcb85d2f 100644 (file)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -663,6 +663,12 @@ static int virtballoon_restore(struct virtio_device *vdev)
 }
 #endif
 
+static int virtballoon_validate(struct virtio_device *vdev)
+{
+       __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
+       return 0;
+}
+
 static unsigned int features[] = {
        VIRTIO_BALLOON_F_MUST_TELL_HOST,
        VIRTIO_BALLOON_F_STATS_VQ,
@@ -675,6 +681,7 @@ static struct virtio_driver virtio_balloon_driver = {
        .driver.name =  KBUILD_MODNAME,
        .driver.owner = THIS_MODULE,
        .id_table =     id_table,
+       .validate =     virtballoon_validate,
        .probe =        virtballoon_probe,
        .remove =       virtballoon_remove,
        .config_changed = virtballoon_changed,