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Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug |
Date: |
Wed, 6 Mar 2013 12:31:35 +0200 |
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
- [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Alexey Kardashevskiy, 2013/03/05
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Michael S. Tsirkin, 2013/03/05
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Alexey Kardashevskiy, 2013/03/05
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Michael S. Tsirkin, 2013/03/05
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Alexey Kardashevskiy, 2013/03/05
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug,
Michael S. Tsirkin <=
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Alexey Kardashevskiy, 2013/03/07
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Michael S. Tsirkin, 2013/03/10
- Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug, Alexey Kardashevskiy, 2013/03/10