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Tsirkin" To: Luiz Augusto von Dentz Cc: Linux Kernel Mailing List , Dan Carpenter , Hulk Robot , Yang Yingliang , Marcel Holtmann , Johan Hedberg , "linux-bluetooth@vger.kernel.org" Subject: Re: [PATCH v3] Bluetooth: virtio_bt: fix device removal Message-ID: <20221007090043-mutt-send-email-mst@kernel.org> References: <20220811094542.268519-1-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 15, 2022 at 11:07:05AM -0700, Luiz Augusto von Dentz wrote: > Hi Michael, > > On Thu, Aug 11, 2022 at 2:46 AM 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 to > > 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’t have any USB URBs in-flight if the transport is not active. > > > > 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() > > Shouldn't the line above be a Fixes tag with the commit hash you are > attempting to fix, other than that I'd be fine to apply these changes. ping? what's going on? > > Signed-off-by: Dan Carpenter > > Reported-by: Hulk Robot > > Signed-off-by: Yang Yingliang > > Signed-off-by: Michael S. Tsirkin > > Message-Id: <20220811080943.198245-1-mst@redhat.com> > > --- > > > > 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_bt.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 = 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); > > @@ -354,8 +361,15 @@ static int virtbt_probe(struct virtio_device *vdev) > > goto failed; > > } > > > > + virtio_device_ready(vdev); > > + err = 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 *vdev) > > > > hci_unregister_dev(hdev); > > virtio_reset_device(vdev); > > + virtbt_close_vdev(vbt); > > > > hci_free_dev(hdev); > > vbt->hdev = NULL; > > -- > > MST > > > > > -- > Luiz Augusto von Dentz