virtio/blk: verify device has config space

Some devices might not implement config space access
(e.g. remoteproc used not to - before 3.9).
virtio/blk needs config space access so make it
fail gracefully if not there.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index cdfbd21e3597..b72c11a10f40 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -575,6 +575,12 @@ static int virtblk_probe(struct virtio_device *vdev)
         u16 min_io_size;
         u8 physical_block_exp, alignment_offset;
 
+        if (!vdev->config->get) {
+                dev_err(&vdev->dev, "%s failure: config access disabled\n",
+                        __func__);
+                return -EINVAL;
+        }
+
         err = ida_simple_get(&vd_index_ida, 0, minor_to_index(1 << MINORBITS),
                              GFP_KERNEL);
         if (err < 0)