Xuan Zhuo
2022-Dec-28 08:31 UTC
[PATCH 4/4] virtio-net: sleep instead of busy waiting for cvq command
On Tue, 27 Dec 2022 01:58:22 -0500, "Michael S. Tsirkin" <mst at redhat.com> wrote:> On Tue, Dec 27, 2022 at 12:33:53PM +0800, Jason Wang wrote: > > On Tue, Dec 27, 2022 at 10:25 AM Xuan Zhuo <xuanzhuo at linux.alibaba.com> wrote: > > > > > > On Mon, 26 Dec 2022 15:49:08 +0800, Jason Wang <jasowang at redhat.com> wrote: > > > > We used to busy waiting on the cvq command this tends to be > > > > problematic since: > > > > > > > > 1) CPU could wait for ever on a buggy/malicous device > > > > 2) There's no wait to terminate the process that triggers the cvq > > > > command > > > > > > > > So this patch switch to use virtqueue_wait_for_used() to sleep with a > > > > timeout (1s) instead of busy polling for the cvq command forever. This > > > > > > I don't think that a fixed 1S is a good choice. > > > > Well, it could be tweaked to be a little bit longer. > > > > One way, as discussed, is to let the device advertise a timeout then > > the driver can validate if it's valid and use that timeout. But it > > needs extension to the spec. > > Controlling timeout from device is a good idea, e.g. hardware devices > would benefit from a shorter timeout, hypervisor devices from a longer > timeout or no timeout.Yes. That is good. Before introducing this feature, I personally like to use "wait", rather than define a timeout. Thanks.> > > > > > Some of the DPUs are very > > > lazy for cvq handle. > > > > Such design needs to be revisited, cvq (control path) should have a > > better priority or QOS than datapath. > > Spec says nothing about this, so driver can't assume this either. > > > > In particular, we will also directly break the device. > > > > It's kind of hardening for malicious devices. > > ATM no amount of hardening can prevent a malicious hypervisor from > blocking the guest. Recovering when a hardware device is broken would be > nice but I think if we do bother then we should try harder to recover, > such as by driving device reset. > > > Also, does your patch break surprise removal? There's no callback > in this case ATM. > > > > > > > I think it is necessary to add a Virtio-Net parameter to allow users to define > > > this timeout by themselves. Although I don't think this is a good way. > > > > Very hard and unfriendly to the end users. > > > > Thanks > > > > > > > > Thanks. > > > > > > > > > > gives the scheduler a breath and can let the process can respond to > > > > asignal. If the device doesn't respond in the timeout, break the > > > > device. > > > > > > > > Signed-off-by: Jason Wang <jasowang at redhat.com> > > > > --- > > > > Changes since V1: > > > > - break the device when timeout > > > > - get buffer manually since the virtio core check more_used() instead > > > > --- > > > > drivers/net/virtio_net.c | 24 ++++++++++++++++-------- > > > > 1 file changed, 16 insertions(+), 8 deletions(-) > > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > > index efd9dd55828b..6a2ea64cfcb5 100644 > > > > --- a/drivers/net/virtio_net.c > > > > +++ b/drivers/net/virtio_net.c > > > > @@ -405,6 +405,7 @@ static void disable_rx_mode_work(struct virtnet_info *vi) > > > > vi->rx_mode_work_enabled = false; > > > > spin_unlock_bh(&vi->rx_mode_lock); > > > > > > > > + virtqueue_wake_up(vi->cvq); > > > > flush_work(&vi->rx_mode_work); > > > > } > > > > > > > > @@ -1497,6 +1498,11 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq, > > > > return !oom; > > > > } > > > > > > > > +static void virtnet_cvq_done(struct virtqueue *cvq) > > > > +{ > > > > + virtqueue_wake_up(cvq); > > > > +} > > > > + > > > > static void skb_recv_done(struct virtqueue *rvq) > > > > { > > > > struct virtnet_info *vi = rvq->vdev->priv; > > > > @@ -1984,6 +1990,8 @@ static int virtnet_tx_resize(struct virtnet_info *vi, > > > > return err; > > > > } > > > > > > > > +static int virtnet_close(struct net_device *dev); > > > > + > > > > /* > > > > * Send command via the control virtqueue and check status. Commands > > > > * supported by the hypervisor, as indicated by feature bits, should > > > > @@ -2026,14 +2034,14 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, > > > > if (unlikely(!virtqueue_kick(vi->cvq))) > > > > return vi->ctrl->status == VIRTIO_NET_OK; > > > > > > > > - /* Spin for a response, the kick causes an ioport write, trapping > > > > - * into the hypervisor, so the request should be handled immediately. > > > > - */ > > > > - while (!virtqueue_get_buf(vi->cvq, &tmp) && > > > > - !virtqueue_is_broken(vi->cvq)) > > > > - cpu_relax(); > > > > + if (virtqueue_wait_for_used(vi->cvq)) { > > > > + virtqueue_get_buf(vi->cvq, &tmp); > > > > + return vi->ctrl->status == VIRTIO_NET_OK; > > > > + } > > > > > > > > - return vi->ctrl->status == VIRTIO_NET_OK; > > > > + netdev_err(vi->dev, "CVQ command timeout, break the virtio device."); > > > > + virtio_break_device(vi->vdev); > > > > + return VIRTIO_NET_ERR; > > > > } > > > > > > > > static int virtnet_set_mac_address(struct net_device *dev, void *p) > > > > @@ -3526,7 +3534,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi) > > > > > > > > /* Parameters for control virtqueue, if any */ > > > > if (vi->has_cvq) { > > > > - callbacks[total_vqs - 1] = NULL; > > > > + callbacks[total_vqs - 1] = virtnet_cvq_done; > > > > names[total_vqs - 1] = "control"; > > > > } > > > > > > > > -- > > > > 2.25.1 > > > > > > > > _______________________________________________ > > > > Virtualization mailing list > > > > Virtualization at lists.linux-foundation.org > > > > https://lists.linuxfoundation.org/mailman/listinfo/virtualization > > > >
Jason Wang
2022-Dec-28 11:41 UTC
[PATCH 4/4] virtio-net: sleep instead of busy waiting for cvq command
On Wed, Dec 28, 2022 at 4:34 PM Xuan Zhuo <xuanzhuo at linux.alibaba.com> wrote:> > On Tue, 27 Dec 2022 01:58:22 -0500, "Michael S. Tsirkin" <mst at redhat.com> wrote: > > On Tue, Dec 27, 2022 at 12:33:53PM +0800, Jason Wang wrote: > > > On Tue, Dec 27, 2022 at 10:25 AM Xuan Zhuo <xuanzhuo at linux.alibaba.com> wrote: > > > > > > > > On Mon, 26 Dec 2022 15:49:08 +0800, Jason Wang <jasowang at redhat.com> wrote: > > > > > We used to busy waiting on the cvq command this tends to be > > > > > problematic since: > > > > > > > > > > 1) CPU could wait for ever on a buggy/malicous device > > > > > 2) There's no wait to terminate the process that triggers the cvq > > > > > command > > > > > > > > > > So this patch switch to use virtqueue_wait_for_used() to sleep with a > > > > > timeout (1s) instead of busy polling for the cvq command forever. This > > > > > > > > I don't think that a fixed 1S is a good choice. > > > > > > Well, it could be tweaked to be a little bit longer. > > > > > > One way, as discussed, is to let the device advertise a timeout then > > > the driver can validate if it's valid and use that timeout. But it > > > needs extension to the spec. > > > > Controlling timeout from device is a good idea, e.g. hardware devices > > would benefit from a shorter timeout, hypervisor devices from a longer > > timeout or no timeout. > > Yes. That is good. > > Before introducing this feature, I personally like to use "wait", rather than > define a timeout.Note that the driver still needs to validate what device advertises to avoid infinite wait. Thanks> > Thanks. > > > > > > > > > > > Some of the DPUs are very > > > > lazy for cvq handle. > > > > > > Such design needs to be revisited, cvq (control path) should have a > > > better priority or QOS than datapath. > > > > Spec says nothing about this, so driver can't assume this either. > > > > > > In particular, we will also directly break the device. > > > > > > It's kind of hardening for malicious devices. > > > > ATM no amount of hardening can prevent a malicious hypervisor from > > blocking the guest. Recovering when a hardware device is broken would be > > nice but I think if we do bother then we should try harder to recover, > > such as by driving device reset. > > > > > > Also, does your patch break surprise removal? There's no callback > > in this case ATM. > > > > > > > > > > I think it is necessary to add a Virtio-Net parameter to allow users to define > > > > this timeout by themselves. Although I don't think this is a good way. > > > > > > Very hard and unfriendly to the end users. > > > > > > Thanks > > > > > > > > > > > Thanks. > > > > > > > > > > > > > gives the scheduler a breath and can let the process can respond to > > > > > asignal. If the device doesn't respond in the timeout, break the > > > > > device. > > > > > > > > > > Signed-off-by: Jason Wang <jasowang at redhat.com> > > > > > --- > > > > > Changes since V1: > > > > > - break the device when timeout > > > > > - get buffer manually since the virtio core check more_used() instead > > > > > --- > > > > > drivers/net/virtio_net.c | 24 ++++++++++++++++-------- > > > > > 1 file changed, 16 insertions(+), 8 deletions(-) > > > > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > > > index efd9dd55828b..6a2ea64cfcb5 100644 > > > > > --- a/drivers/net/virtio_net.c > > > > > +++ b/drivers/net/virtio_net.c > > > > > @@ -405,6 +405,7 @@ static void disable_rx_mode_work(struct virtnet_info *vi) > > > > > vi->rx_mode_work_enabled = false; > > > > > spin_unlock_bh(&vi->rx_mode_lock); > > > > > > > > > > + virtqueue_wake_up(vi->cvq); > > > > > flush_work(&vi->rx_mode_work); > > > > > } > > > > > > > > > > @@ -1497,6 +1498,11 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq, > > > > > return !oom; > > > > > } > > > > > > > > > > +static void virtnet_cvq_done(struct virtqueue *cvq) > > > > > +{ > > > > > + virtqueue_wake_up(cvq); > > > > > +} > > > > > + > > > > > static void skb_recv_done(struct virtqueue *rvq) > > > > > { > > > > > struct virtnet_info *vi = rvq->vdev->priv; > > > > > @@ -1984,6 +1990,8 @@ static int virtnet_tx_resize(struct virtnet_info *vi, > > > > > return err; > > > > > } > > > > > > > > > > +static int virtnet_close(struct net_device *dev); > > > > > + > > > > > /* > > > > > * Send command via the control virtqueue and check status. Commands > > > > > * supported by the hypervisor, as indicated by feature bits, should > > > > > @@ -2026,14 +2034,14 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, > > > > > if (unlikely(!virtqueue_kick(vi->cvq))) > > > > > return vi->ctrl->status == VIRTIO_NET_OK; > > > > > > > > > > - /* Spin for a response, the kick causes an ioport write, trapping > > > > > - * into the hypervisor, so the request should be handled immediately. > > > > > - */ > > > > > - while (!virtqueue_get_buf(vi->cvq, &tmp) && > > > > > - !virtqueue_is_broken(vi->cvq)) > > > > > - cpu_relax(); > > > > > + if (virtqueue_wait_for_used(vi->cvq)) { > > > > > + virtqueue_get_buf(vi->cvq, &tmp); > > > > > + return vi->ctrl->status == VIRTIO_NET_OK; > > > > > + } > > > > > > > > > > - return vi->ctrl->status == VIRTIO_NET_OK; > > > > > + netdev_err(vi->dev, "CVQ command timeout, break the virtio device."); > > > > > + virtio_break_device(vi->vdev); > > > > > + return VIRTIO_NET_ERR; > > > > > } > > > > > > > > > > static int virtnet_set_mac_address(struct net_device *dev, void *p) > > > > > @@ -3526,7 +3534,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi) > > > > > > > > > > /* Parameters for control virtqueue, if any */ > > > > > if (vi->has_cvq) { > > > > > - callbacks[total_vqs - 1] = NULL; > > > > > + callbacks[total_vqs - 1] = virtnet_cvq_done; > > > > > names[total_vqs - 1] = "control"; > > > > > } > > > > > > > > > > -- > > > > > 2.25.1 > > > > > > > > > > _______________________________________________ > > > > > Virtualization mailing list > > > > > Virtualization at lists.linux-foundation.org > > > > > https://lists.linuxfoundation.org/mailman/listinfo/virtualization > > > > > > >