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SubjectRe: [PATCH net] vsock/virtio: enable VQs early on probe
On Tue, Mar 22, 2022 at 10:09:06AM -0400, Michael S. Tsirkin wrote:
>On Tue, Mar 22, 2022 at 03:05:00PM +0100, Stefano Garzarella wrote:
>> On Tue, Mar 22, 2022 at 09:36:14AM -0400, Michael S. Tsirkin wrote:
>> > On Tue, Mar 22, 2022 at 11:38:23AM +0100, Stefano Garzarella wrote:
>> > > virtio spec requires drivers to set DRIVER_OK before using VQs.
>> > > This is set automatically after probe returns, but virtio-vsock
>> > > driver uses VQs in the probe function to fill rx and event VQs
>> > > with new buffers.
>> >
>> >
>> > So this is a spec violation. absolutely.
>> >
>> > > Let's fix this, calling virtio_device_ready() before using VQs
>> > > in the probe function.
>> > >
>> > > Fixes: 0ea9e1d3a9e3 ("VSOCK: Introduce virtio_transport.ko")
>> > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>> > > ---
>> > > net/vmw_vsock/virtio_transport.c | 2 ++
>> > > 1 file changed, 2 insertions(+)
>> > >
>> > > diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>> > > index 5afc194a58bb..b1962f8cd502 100644
>> > > --- a/net/vmw_vsock/virtio_transport.c
>> > > +++ b/net/vmw_vsock/virtio_transport.c
>> > > @@ -622,6 +622,8 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
>> > > INIT_WORK(&vsock->event_work, virtio_transport_event_work);
>> > > INIT_WORK(&vsock->send_pkt_work, virtio_transport_send_pkt_work);
>> > >
>> > > + virtio_device_ready(vdev);
>> > > +
>> > > mutex_lock(&vsock->tx_lock);
>> > > vsock->tx_run = true;
>> > > mutex_unlock(&vsock->tx_lock);
>> >
>> > Here's the whole code snippet:
>> >
>> >
>> > mutex_lock(&vsock->tx_lock);
>> > vsock->tx_run = true;
>> > mutex_unlock(&vsock->tx_lock);
>> >
>> > mutex_lock(&vsock->rx_lock);
>> > virtio_vsock_rx_fill(vsock);
>> > vsock->rx_run = true;
>> > mutex_unlock(&vsock->rx_lock);
>> >
>> > mutex_lock(&vsock->event_lock);
>> > virtio_vsock_event_fill(vsock);
>> > vsock->event_run = true;
>> > mutex_unlock(&vsock->event_lock);
>> >
>> > if (virtio_has_feature(vdev, VIRTIO_VSOCK_F_SEQPACKET))
>> > vsock->seqpacket_allow = true;
>> >
>> > vdev->priv = vsock;
>> > rcu_assign_pointer(the_virtio_vsock, vsock);
>> >
>> > mutex_unlock(&the_virtio_vsock_mutex);
>> >
>> >
>> > I worry that this is not the only problem here:
>> > seqpacket_allow and setting of vdev->priv at least after
>> > device is active look suspicious.
>>
>> Right, so if you agree I'll move these before virtio_device_ready().
>>
>> > E.g.:
>> >
>> > static void virtio_vsock_event_done(struct virtqueue *vq)
>> > {
>> > struct virtio_vsock *vsock = vq->vdev->priv;
>> >
>> > if (!vsock)
>> > return;
>> > queue_work(virtio_vsock_workqueue, &vsock->event_work);
>> > }
>> >
>> > looks like it will miss events now they will be reported earlier.
>> > One might say that since vq has been kicked it might send
>> > interrupts earlier too so not a new problem, but
>> > there's a chance device actually waits until DRIVER_OK
>> > to start operating.
>>
>> Yes I see, should I break into 2 patches (one where I move the code already
>> present and this one)?
>>
>> Maybe a single patch is fine since it's the complete solution.
>>
>> Thank you for the detailed explanation,
>> Stefano
>
>Two I think since movement can be backported to before the hardening
>effort.

Yep, maybe 3 since seqpacket was added later.

Thanks,
Stefano

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