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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Tue, 11 Oct 2022 12:57:30 -0700
Message-ID: <CABBYNZJ9cj2RuJSyKcfV33N4kn1aqNQdJLFj8T5PEeJpGtRxWw@mail.gmail.com>
Subject: Re: [PATCH v3 resend] Bluetooth: virtio_bt: fix device removal
To:     Igor Skalkin <igor.skalkin@opensynergy.com>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        linux-kernel@vger.kernel.org,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Hulk Robot <hulkci@huawei.com>,
        Yang Yingliang <yangyingliang@huawei.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        linux-bluetooth@vger.kernel.org
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Hi Michael,

On Tue, Oct 11, 2022 at 5:18 AM Igor Skalkin
<igor.skalkin@opensynergy.com> wrote:
>
> Tested, works fine in our projects.
>
> Tested-by: Igor Skalkin <Igor.Skalkin@opensynergy.com>
>
> On 10/10/22 19:14, Michael S. Tsirkin wrote:
> > 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.
> >
> > NB: This is a hacky way to handle this - virtbt_{open,close} as NOP is
> > not really what a driver is supposed to be doing. These are transport
> > enable/disable callbacks from the BT core towards the driver. It maps t=
o
> > a device being enabled/disabled by something like bluetoothd for
> > example. So if disabled, users expect that no resources/queues are in
> > use.  It does work with all other transports like USB, SDIO, UART etc.
> > There should be no buffer used if the device is powered off. We also
> > don=E2=80=99t have any USB URBs in-flight if the transport is not activ=
e.
> >
> > The way to implement a proper fix would be using vq reset if supported,
> > or even using a full device reset.
> >
> > The cost of the hack is a single skb wasted on an unused bt device.
> >
> > NB2: with this fix in place driver still suffers from a race condition
> > if an interrupt triggers while device is being reset.  To fix, in the
> > virtbt_close() callback we should deactivate all interrupts.  To be
> > fixed.
> >
> > squashed fixup: bluetooth: virtio_bt: fix an error code in probe()
> >
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > Reported-by: Hulk Robot <hulkci@huawei.com>
> > Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > Message-Id: <20220811080943.198245-1-mst@redhat.com>

Ive pushed this one.

> > ---
> >
> > resending due to v3 having been dropped
> > changes from v2:
> >       tkeaked commit log to make lines shorter
> > changes from v1:
> >       fixed error handling
> >
> >   drivers/bluetooth/virtio_bt.c | 19 +++++++++++++++++--
> >   1 file changed, 17 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/bluetooth/virtio_bt.c b/drivers/bluetooth/virtio_b=
t.c
> > index 67c21263f9e0..f6d699fed139 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 =3D 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 =3D hci_get_drvdata(hdev);
> > +     return 0;
> > +}
> > +
> > +static int virtbt_close_vdev(struct virtio_bluetooth *vbt)
> > +{
> >       int i;
> >
> >       cancel_work_sync(&vbt->rx);
> > @@ -354,8 +361,15 @@ static int virtbt_probe(struct virtio_device *vdev=
)
> >               goto failed;
> >       }
> >
> > +     virtio_device_ready(vdev);
> > +     err =3D virtbt_open_vdev(vbt);
> > +     if (err)
> > +             goto open_failed;
> > +
> >       return 0;
> >
> > +open_failed:
> > +     hci_free_dev(hdev);
> >   failed:
> >       vdev->config->del_vqs(vdev);
> >       return err;
> > @@ -368,6 +382,7 @@ static void virtbt_remove(struct virtio_device *vde=
v)
> >
> >       hci_unregister_dev(hdev);
> >       virtio_reset_device(vdev);
> > +     virtbt_close_vdev(vbt);
> >
> >       hci_free_dev(hdev);
> >       vbt->hdev =3D NULL;
>
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Luiz Augusto von Dentz