linux-kernel - [PATCH] Bluetooth: virtio

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Date:   Thu, 25 Nov 2021 12:44:48 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-bluetooth@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH] Bluetooth: virtio_bt: fix device removal

Device removal is clearly out of virtio spec: it attempts to remove
unused buffers from a VQ before invoking device reset. To fix, make
open/close NOPs and do all cleanup/setup in probe/remove.

The cost here is a single skb wasted on an unused bt device - which
seems modest.

NB: with this fix in place driver still suffers from a race condition if
an interrupt triggers while device is being reset. Work on a fix for
that issue is in progress.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---

Note: completely untested, in particular the device isn't supported in QEMU.
Please do not queue directly - please help review and test and ack,
and I will queue this together with reset fixes.
Thanks!


 drivers/bluetooth/virtio_bt.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/virtio_bt.c b/drivers/bluetooth/virtio_bt.c
index 24a9258962fa..aea33ba9522c 100644
--- a/drivers/bluetooth/virtio_bt.c
+++ b/drivers/bluetooth/virtio_bt.c
@@ -50,8 +50,11 @@ static int virtbt_add_inbuf(struct virtio_bluetooth *vbt)
 
 static int virtbt_open(struct hci_dev *hdev)
 {
-	struct virtio_bluetooth *vbt = hci_get_drvdata(hdev);
+	return 0;
+}
 
+static int virtbt_open_vdev(struct virtio_bluetooth *vbt)
+{
 	if (virtbt_add_inbuf(vbt) < 0)
 		return -EIO;
 
@@ -61,7 +64,11 @@ static int virtbt_open(struct hci_dev *hdev)
 
 static int virtbt_close(struct hci_dev *hdev)
 {
-	struct virtio_bluetooth *vbt = hci_get_drvdata(hdev);
+	return 0;
+}
+
+static int virtbt_close_vdev(struct virtio_bluetooth *vbt)
+{
 	int i;
 
 	cancel_work_sync(&vbt->rx);
@@ -351,8 +358,14 @@ static int virtbt_probe(struct virtio_device *vdev)
 		goto failed;
 	}
 
+	virtio_device_ready(vdev);
+	if (virtbt_open_vdev(vbt))
+		goto open_failed;
+
 	return 0;
 
+open_failed:
+	hci_free_dev(hdev);
 failed:
 	vdev->config->del_vqs(vdev);
 	return err;
@@ -365,6 +378,7 @@ static void virtbt_remove(struct virtio_device *vdev)
 
 	hci_unregister_dev(hdev);
 	vdev->config->reset(vdev);
+	virtbt_close_vdev(vbt);
 
 	hci_free_dev(hdev);
 	vbt->hdev = NULL;
-- 
MST