From 6d62c37f1991aafc872f8d8be8ac60e57ede8605 Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Wed, 15 Oct 2014 10:22:32 +1030
Subject: virtio_blk: enable VQs early on restore

virtio spec requires drivers to set DRIVER_OK before using VQs.
This is set automatically after restore returns, virtio block violated
this rule on restore by restarting queues, which might in theory
cause the VQ to be used directly within restore.

To fix, call virtio_device_ready before using starting queues.

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

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 34ec273..930fee8 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -804,10 +804,13 @@ static int virtblk_restore(struct virtio_device *vdev)
 	int ret;
 
 	ret = init_vq(vdev->priv);
-	if (!ret)
-		blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
+	if (ret)
+		return ret;
+
+	virtio_device_ready(vdev);
 
-	return ret;
+	blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
+	return 0;
 }
 #endif
 
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