Re: [Qemu-devel] [RFC 2/9] virtio-pci: support host notifiers in TCG mode

[Paolo Bonzini <pbonzini@redhat.com>]

Il 25/07/2012 00:33, Nicholas A. Bellinger ha scritto:
> From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> 
> Normally host notifiers are only used together with vhost-net in KVM
> mode.  It is occassionally useful to use vhost with TCG mode, mainly for
> testing and development.  This isn't hard to achieve, simply fall back
> to notifying the host notifier manually from qemu if KVM mode is
> disabled.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> Cc: Anthony Liguori <aliguori@us.ibm.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> ---
>  hw/virtio-pci.c |   23 ++++++++++++++++++++---
>  hw/virtio.c     |    7 +++++++
>  2 files changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 4e03f0b..538eef4 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -249,6 +249,25 @@ void virtio_pci_reset(DeviceState *d)
>      proxy->flags &= ~VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
>  }
>  
> +static void virtio_pci_queue_notify(VirtIOPCIProxy *proxy, uint32_t n)
> +{
> +    VirtQueue *vq;
> +    EventNotifier *notifier;
> +
> +    if (n >= VIRTIO_PCI_QUEUE_MAX) {
> +        return;
> +    }
> +
> +    vq = virtio_get_queue(proxy->vdev, n);
> +    notifier = virtio_queue_get_host_notifier(vq);
> +    if (event_notifier_valid(notifier)) {
> +        printf("notifying vq %u host notifier from userspace\n", n);

Debug printf.

> +        event_notifier_notify(notifier);
> +    } else {
> +        virtio_queue_notify_vq(vq);
> +    }

This can be done directly in virtio_queue_notify, there is nothing
specific to virtio-pci.

> +}
> +
>  static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
>  {
>      VirtIOPCIProxy *proxy = opaque;
> @@ -278,9 +297,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
>              vdev->queue_sel = val;
>          break;
>      case VIRTIO_PCI_QUEUE_NOTIFY:
> -        if (val < VIRTIO_PCI_QUEUE_MAX) {
> -            virtio_queue_notify(vdev, val);
> -        }
> +        virtio_pci_queue_notify(proxy, val);
>          break;
>      case VIRTIO_PCI_STATUS:
>          if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> diff --git a/hw/virtio.c b/hw/virtio.c
> index d146f86..36a18b5 100644
> --- a/hw/virtio.c
> +++ b/hw/virtio.c
> @@ -536,6 +536,11 @@ void virtio_reset(void *opaque)
>          vdev->vq[i].signalled_used = 0;
>          vdev->vq[i].signalled_used_valid = false;
>          vdev->vq[i].notification = true;
> +
> +        assert(!event_notifier_valid(&vdev->vq[i].guest_notifier));
> +        assert(!event_notifier_valid(&vdev->vq[i].host_notifier));
> +        vdev->vq[i].guest_notifier = EVENT_NOTIFIER_INITIALIZER;
> +        vdev->vq[i].host_notifier = EVENT_NOTIFIER_INITIALIZER;

Given the assertions, the assignments should be no-ops.

>      }
>  }
>  
> @@ -905,6 +910,8 @@ VirtIODevice *virtio_common_init(const char *name, uint16_t device_id,
>      for(i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
>          vdev->vq[i].vector = VIRTIO_NO_VECTOR;
>          vdev->vq[i].vdev = vdev;
> +        vdev->vq[i].guest_notifier = EVENT_NOTIFIER_INITIALIZER;
> +        vdev->vq[i].host_notifier = EVENT_NOTIFIER_INITIALIZER;
>      }
>  
>      vdev->name = name;
>