On Wed, 2008-03-26 at 17:07 +0100, Christian Ehrhardt wrote:
> Hollis Blanchard wrote:
> > On Tue, 2008-03-25 at 14:45 +0100, Christian Ehrhardt wrote:
> >> => from one not yet defined point our guest seems to receive absolutely nothing
> >> => when the guest is hanging it sends nfs requests which are seen externally, but it does not seem to get the respones
> >> => the arp requests for the guest are repeated - maybe we can add some very verbose debug in the guest virtio code and activate it when we see that it is already hanging
> >> => ideas:
> >> - maybe some buffer/memory runs out and so incoming packets won't be received anymore
> >> - we break something in virtio / incoming interrupts (or maybe a lock) and from that point no receive is possible
> >>
> > Could we be missing interrupts? Can you add a guest kernel timer that
> > calls virtio_poll() regularly?
>
>
> Working but not the final solution.
> Preliminary workaround patch attached
>
> Atm I think we might disable interrupts and polling at the same time.
For disabled interrupts you mean that the VRING_AVAIL_F_NO_INTERRUPT
flag is set or really your s390 replacement to cli?
If it's just the flag you can ignore it in the host (virtio-net.c).
btw: I didn't see any VRING_USED_F_NO_NOTIFY on the guest side.
It is only for optimizations so just put it on your todo list.
>
> Good message: it was slow, but I saw a login prompt ;-)
> here a guest "cat /proc/cpuinfo"
> cat /proc/cpuinfo
> processor : 0
> cpu : unknown (00000000)
> clock : 666.666660MHz
> revision : 0.0 (pvr 0000 0000)
> bogomips : 2490.36
> timebase : 666666660
> platform : Bamboo
>
> That means once we found the reason for that staving virto-net device we should have a basic working linux guest.
>
> P.S. added virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx (this time) to get any virtio-net related suggestions from there too
>
> plain text document attachment (virtio-net-poll-on-timer)
> Subject: [PATCH] kvmppc virtio-net: workaround for lost interrupt/polling
>
> From: Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>
>
> This patch is (atm) just a debug workaround. The issue is that virtio-net
> works fine for a while but then "something" happens and we see neither
> vp_interrupts nor calls to virtnet_poll anymore.
> Looking at the network traffic shows that the kvm guest still sends packets
> via virtio-net and that userspace tries to deliver things to the guest, but
> the guest receives nothing.
> Somehow it loks loke polling and interrupts are disables (more debugging
> needed).
> For now anyone can continue with that workaround patch (which is
> very slow, I had no time to tune the polling interval yet).
> There's an ugly fixme, but I don't yet know what exactly causes this BUG()
> to trigger so thats the way to get it out for now.
> I'll update the patch once I have an improved version.
>
> Signed-off-by: Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>
> ---
>
> [diffstat]
> virtio_net.c | 36 ++++++++++++++++++++++++++++++------
> 1 files changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -194,17 +194,22 @@ again:
> received++;
> }
>
> +
> /* FIXME: If we oom and completely run out of inbufs, we need
> * to start a timer trying to fill more. */
> if (vi->num < vi->max / 2)
> try_fill_recv(vi);
>
> - /* Out of packets? */
> - if (received < budget) {
> - netif_rx_complete(vi->dev, napi);
> - if (unlikely(!vi->rvq->vq_ops->enable_cb(vi->rvq))
> - && netif_rx_reschedule(vi->dev, napi))
> - goto again;
> + /* FIXME - fails when called by workaround timer polling (sometimes) */
> + if (budget != 42)
> + {
> + /* Out of packets? */
> + if (received < budget) {
> + netif_rx_complete(vi->dev, napi);
> + if (unlikely(!vi->rvq->vq_ops->enable_cb(vi->rvq))
> + && netif_rx_reschedule(vi->dev, napi))
> + goto again;
> + }
> }
>
> return received;
> @@ -294,6 +299,17 @@ again:
> return 0;
> }
>
> +static struct timer_list viopoll_timer;
> +static void virtio_poll_wrap(unsigned long dev)
> +{
> + struct virtnet_info *vi = netdev_priv((struct net_device *)dev);
> + /* poll more often if polling received something */
> + if (virtnet_poll(&vi->napi, 42))
> + mod_timer(&viopoll_timer, get_jiffies_64() + (HZ/150));
> + else
> + mod_timer(&viopoll_timer, get_jiffies_64() + (HZ/25));
> +}
> +
> static int virtnet_open(struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> @@ -308,12 +324,20 @@ static int virtnet_open(struct net_devic
> vi->rvq->vq_ops->disable_cb(vi->rvq);
> __netif_rx_schedule(dev, &vi->napi);
> }
> +
> + // DEBUG (Missing interrupts ?)
> + setup_timer(&viopoll_timer, virtio_poll_wrap, (unsigned long)(dev));
> + mod_timer(&viopoll_timer, get_jiffies_64() + HZ);
> + printk("%s - set up virtnet_poll timer\n", __func__);
> +
> return 0;
> }
>
> static int virtnet_close(struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> +
> + del_timer(&viopoll_timer);
>
> napi_disable(&vi->napi);
>
>
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