Re: [Qemu-devel] [PATCH v5] vhost-user interrupt management fixes

[Didier Pallard <didier.pallard@6wind.com>]

Hi victor,

I'm sorry, i didn't get time to work on this patch.
Thanks for your work.

didier


On 02/18/2016 03:12 PM, Victor Kaplansky wrote:
> Since guest_mask_notifier can not be used in vhost-user mode due
> to buffering implied by unix control socket, force
> use_mask_notifier on virtio devices of vhost-user interfaces, and
> send correct callfd to the guest at vhost start.
>
> Using guest_notifier_mask function in vhost-user case may
> break interrupt mask paradigm, because mask/unmask is not
> really done when returning from guest_notifier_mask call, instead
> message is posted in a unix socket, and processed later.
>
> Add an option boolean flag 'use_mask_notifier' to disable the use
> of guest_notifier_mask in virtio pci.
>
> Signed-off-by: Didier Pallard <didier.pallard@6wind.com>
> Signed-off-by: Victor Kaplansky <victork@redhat.com>
> ---
> v5 changes:
>    - rebased to mst tree.
>    - removed a traling space.
>
> v4 changes:
>   In respond to Michael S. Tsirkin comments:
>     - changed the name of new field to use_guest_notifier_mask
>     - clarified comments
>     - vhost_virtqueue_mask() called for unmask
>     - cosmetic changes
>     - moved the initialization of the new field from virtio_reset
>       to virtio_init.
>
> v3 changes:
>   In respond to Michael S. Tsirkin comments:
>     - vhost_net.c: removed dependency on virtio-pci.h
>     - vhost.c: simplified the check for vhost-user backend,
>       replaced by checking use_mask_notifier; added comment
>       explaining why vring for vhost-user initialized in
>       unmasked state;
>     - cosmetic fixes.
>
> v2 changes:
>   - a new boolean field is added to all virtio devices instead
>     of defining a property in some virtio-pci devices.
>
>   include/hw/virtio/virtio.h |  1 +
>   hw/net/vhost_net.c         | 15 +++++++++++++--
>   hw/virtio/vhost.c          |  9 +++++++++
>   hw/virtio/virtio-pci.c     | 14 ++++++++------
>   hw/virtio/virtio.c         |  1 +
>   5 files changed, 32 insertions(+), 8 deletions(-)
>
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 108cdb0f..c38a2fef 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -90,6 +90,7 @@ struct VirtIODevice
>       VMChangeStateEntry *vmstate;
>       char *bus_name;
>       uint8_t device_endian;
> +    bool use_guest_notifier_mask;
>       QLIST_HEAD(, VirtQueue) *vector_queues;
>   };
>   
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index b2428324..6e1032fc 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -284,8 +284,19 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
>       }
>   
>       for (i = 0; i < total_queues; i++) {
> -        vhost_net_set_vq_index(get_vhost_net(ncs[i].peer), i * 2);
> -    }
> +        struct vhost_net *net;
> +
> +        net = get_vhost_net(ncs[i].peer);
> +        vhost_net_set_vq_index(net, i * 2);
> +
> +        /* Suppress the masking guest notifiers on vhost user
> +         * because vhost user doesn't interrupt masking/unmasking
> +         * properly.
> +         */
> +        if (net->nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER) {
> +                dev->use_guest_notifier_mask = false;
> +        }
> +     }
>   
>       r = k->set_guest_notifiers(qbus->parent, total_queues * 2, true);
>       if (r < 0) {
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 9f8ac38c..72d0c9e9 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -875,6 +875,14 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
>       /* Clear and discard previous events if any. */
>       event_notifier_test_and_clear(&vq->masked_notifier);
>   
> +    /* Init vring in unmasked state, unless guest_notifier_mask
> +     * will do it later.
> +     */
> +    if (!vdev->use_guest_notifier_mask) {
> +        /* TODO: check and handle errors. */
> +        vhost_virtqueue_mask(dev, vdev, idx, false);
> +    }
> +
>       return 0;
>   
>   fail_kick:
> @@ -1167,6 +1175,7 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
>       struct vhost_vring_file file;
>   
>       if (mask) {
> +        assert(vdev->use_guest_notifier_mask);
>           file.fd = event_notifier_get_fd(&hdev->vqs[index].masked_notifier);
>       } else {
>           file.fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vvq));
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 5494ff4a..440776c0 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -806,7 +806,7 @@ static int kvm_virtio_pci_vector_use(VirtIOPCIProxy *proxy, int nvqs)
>           /* If guest supports masking, set up irqfd now.
>            * Otherwise, delay until unmasked in the frontend.
>            */
> -        if (k->guest_notifier_mask) {
> +        if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
>               ret = kvm_virtio_pci_irqfd_use(proxy, queue_no, vector);
>               if (ret < 0) {
>                   kvm_virtio_pci_vq_vector_release(proxy, vector);
> @@ -822,7 +822,7 @@ undo:
>           if (vector >= msix_nr_vectors_allocated(dev)) {
>               continue;
>           }
> -        if (k->guest_notifier_mask) {
> +        if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
>               kvm_virtio_pci_irqfd_release(proxy, queue_no, vector);
>           }
>           kvm_virtio_pci_vq_vector_release(proxy, vector);
> @@ -849,7 +849,7 @@ static void kvm_virtio_pci_vector_release(VirtIOPCIProxy *proxy, int nvqs)
>           /* If guest supports masking, clean up irqfd now.
>            * Otherwise, it was cleaned when masked in the frontend.
>            */
> -        if (k->guest_notifier_mask) {
> +        if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
>               kvm_virtio_pci_irqfd_release(proxy, queue_no, vector);
>           }
>           kvm_virtio_pci_vq_vector_release(proxy, vector);
> @@ -882,7 +882,7 @@ static int virtio_pci_vq_vector_unmask(VirtIOPCIProxy *proxy,
>       /* If guest supports masking, irqfd is already setup, unmask it.
>        * Otherwise, set it up now.
>        */
> -    if (k->guest_notifier_mask) {
> +    if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
>           k->guest_notifier_mask(vdev, queue_no, false);
>           /* Test after unmasking to avoid losing events. */
>           if (k->guest_notifier_pending &&
> @@ -905,7 +905,7 @@ static void virtio_pci_vq_vector_mask(VirtIOPCIProxy *proxy,
>       /* If guest supports masking, keep irqfd but mask it.
>        * Otherwise, clean it up now.
>        */
> -    if (k->guest_notifier_mask) {
> +    if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
>           k->guest_notifier_mask(vdev, queue_no, true);
>       } else {
>           kvm_virtio_pci_irqfd_release(proxy, queue_no, vector);
> @@ -1022,7 +1022,9 @@ static int virtio_pci_set_guest_notifier(DeviceState *d, int n, bool assign,
>           event_notifier_cleanup(notifier);
>       }
>   
> -    if (!msix_enabled(&proxy->pci_dev) && vdc->guest_notifier_mask) {
> +    if (!msix_enabled(&proxy->pci_dev) &&
> +        vdev->use_guest_notifier_mask &&
> +        vdc->guest_notifier_mask) {
>           vdc->guest_notifier_mask(vdev, n, !assign);
>       }
>   
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 90f25451..e365960b 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -1677,6 +1677,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
>       vdev->vmstate = qemu_add_vm_change_state_handler(virtio_vmstate_change,
>                                                        vdev);
>       vdev->device_endian = virtio_default_endian();
> +    vdev->use_guest_notifier_mask = true;
>   }
>   
>   hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)