On Wed, Mar 06, 2013 at 09:57:40AM +1100, Alexey Kardashevskiy wrote: > On 06/03/13 01:23, Michael S. Tsirkin wrote: > >On Wed, Mar 06, 2013 at 12:21:47AM +1100, Alexey Kardashevskiy wrote: > >>On 05/03/13 23:56, Michael S. Tsirkin wrote: > >>>>The patch f56a12475ff1b8aa61210d08522c3c8aaf0e2648 "vhost: backend > >>>>masking support" breaks virtio-net + vhost=on on PPC64 platform. > >>>> > >>>>The problem command line is: > >>>>1) -netdev tap,id=tapnet,ifname=tap0,script=qemu-ifup.sh,vhost=on \ > >>>>-device virtio-net-pci,netdev=tapnet,addr=0.0 \ > >>> > >>>I think the issue is irqfd in not supported on kvm ppc. > >> > >>How can I make sure this is the case? Some work has been done there > >>recently but midnight is quite late to figure this out :) > > > >Look in virtio_pci_set_guest_notifiers, what is the > >value of with_irqfd? > > bool with_irqfd = msix_enabled(&proxy->pci_dev) && > > kvm_msi_via_irqfd_enabled(); > > > >Also check what each of the values in the expression above is. > > Yes, ppc does not have irqfd as kvm_msi_via_irqfd_enabled() returned "false". > > >>>Could you please check this: > >>> > >>>+ /* If guest supports masking, set up irqfd now. > >>>+ * Otherwise, delay until unmasked in the frontend. > >>>+ */ > >>>+ if (proxy->vdev->guest_notifier_mask) { > >>>+ ret = kvm_virtio_pci_irqfd_use(proxy, queue_no, vector); > >>>+ if (ret < 0) { > >>>+ kvm_virtio_pci_vq_vector_release(proxy, vector); > >>>+ goto undo; > >>>+ } > >>>+ } > >>> > >>> > >>>Could you please add a printf before "undo" and check whether the > >>>error path above is triggered? > >> > >> > >>Checked, it is not triggered. > >> > >> > >>-- > >>Alexey > > > >I think I get it. > >Does the following help (probably not the right thing to do, but just > >for testing): > > > It did not compile (no "queue_no") :) I changed it a bit and now > vhost=on works fine: > > diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c > index a869f53..df1e443 100644 > --- a/hw/virtio-pci.c > +++ b/hw/virtio-pci.c > @@ -798,6 +798,10 @@ static int > virtio_pci_set_guest_notifiers(DeviceState *d, int nvqs, bool > assign) > if (r < 0) { > goto assign_error; > } > + > + if (!with_irqfd && proxy->vdev->guest_notifier_mask) { > + proxy->vdev->guest_notifier_mask(proxy->vdev, n, !assign); > + } > } > > /* Must set vector notifier after guest notifier has been assigned */ > >
I see, OK, the issue is that vhost now starts in a masked state and no one unmasks it. While the patch will work I think, it does not benefit from backend masking, the right thing to do is to add mask notifiers, like what the irqfd path does. Will look into this, thanks. -- MST