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Date: Tue, 22 Mar 2022 15:36:31 +0100 From: Stefano Garzarella <sgarzare@...hat.com> To: "Michael S. Tsirkin" <mst@...hat.com> Cc: netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Stefan Hajnoczi <stefanha@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, Paolo Abeni <pabeni@...hat.com> Subject: Re: [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@...hat.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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