virtio: add legacy feature table support

virtio-blk has some legacy feature bits that modern drivers
must not negotiate, but are needed for old legacy hosts
(that e.g. don't support virtio-scsi).
Allow a separate legacy feature table for such cases.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index d6359a5d5d4e..f70411eb9d27 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -130,6 +130,8 @@ int virtio_device_restore(struct virtio_device *dev);
  * @id_table: the ids serviced by this driver.
  * @feature_table: an array of feature numbers supported by this driver.
  * @feature_table_size: number of entries in the feature table array.
+ * @feature_table_legacy: same as feature_table but when working in legacy mode.
+ * @feature_table_size_legacy: number of entries in feature table legacy array.
  * @probe: the function to call when a device is found.  Returns 0 or -errno.
  * @remove: the function to call when a device is removed.
  * @config_changed: optional function to call when the device configuration
@@ -140,6 +142,8 @@ struct virtio_driver {
         const struct virtio_device_id *id_table;
         const unsigned int *feature_table;
         unsigned int feature_table_size;
+        const unsigned int *feature_table_legacy;
+        unsigned int feature_table_size_legacy;
         int (*probe)(struct virtio_device *dev);
         void (*scan)(struct virtio_device *dev);
         void (*remove)(struct virtio_device *dev);