linux-kernel - [PATCH] virtio_balloon: fix up endian-ness for free cmd id

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Date:   Mon, 27 Jul 2020 12:03:43 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, David Hildenbrand <david@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Liang Li <liang.z.li@...el.com>,
        Wei Wang <wei.w.wang@...el.com>,
        virtualization@...ts.linux-foundation.org,
        Alexander Duyck <alexander.duyck@...il.com>
Subject: [PATCH] virtio_balloon: fix up endian-ness for free cmd id

free cmd id is read using virtio endian, spec says all fields
in balloon are LE. Fix it up.

Fixes: 86a559787e6f ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT")
Cc: stable@...r.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 drivers/virtio/virtio_balloon.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 774deb65a9bb..798ec304fe3e 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -578,10 +578,14 @@ static int init_vqs(struct virtio_balloon *vb)
 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
 {
 	if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
-			       &vb->config_read_bitmap))
+			       &vb->config_read_bitmap)) {
 		virtio_cread(vb->vdev, struct virtio_balloon_config,
 			     free_page_hint_cmd_id,
 			     &vb->cmd_id_received_cache);
+		/* Legacy balloon config space is LE, unlike all other devices. */
+		if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
+			vb->cmd_id_received_cache = le32_to_cpu((__force __le32)vb->cmd_id_received_cache);
+	}
 
 	return vb->cmd_id_received_cache;
 }
-- 
MST