Re: [Qemu-devel] [PATCH 1/2] virtio: allow per-device-class legacy features

[Jason Wang <jasowang@redhat.com>]

On 2016年11月04日 19:01, Michael S. Tsirkin wrote:
> Legacy features are those that transitional devices only
> expose on the legacy interface.
> Allow different ones per device class.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>   include/hw/virtio/virtio.h | 5 +++++
>   hw/s390x/virtio-ccw.c      | 4 +++-
>   hw/virtio/virtio-pci.c     | 4 +++-
>   hw/virtio/virtio.c         | 2 ++
>   4 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index f12a1a8..bdb3c4b 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -113,6 +113,11 @@ typedef struct VirtioDeviceClass {
>       void (*set_config)(VirtIODevice *vdev, const uint8_t *config);
>       void (*reset)(VirtIODevice *vdev);
>       void (*set_status)(VirtIODevice *vdev, uint8_t val);
> +    /* For transitional devices, this is a bitmap of features
> +     * that are only exposed on the legacy interface but not
> +     * the modern one.
> +     */
> +    uint64_t legacy_features;
>       /* Test and clear event pending status.
>        * Should be called after unmask to avoid losing events.
>        * If backend does not support masking,
> diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> index 7d7f8f6..f5c1d98 100644
> --- a/hw/s390x/virtio-ccw.c
> +++ b/hw/s390x/virtio-ccw.c
> @@ -303,6 +303,8 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
>           if (!ccw.cda) {
>               ret = -EFAULT;
>           } else {
> +            VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
> +
>               features.index = address_space_ldub(&address_space_memory,
>                                                   ccw.cda
>                                                   + sizeof(features.features),
> @@ -312,7 +314,7 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
>                   if (dev->revision >= 1) {
>                       /* Don't offer legacy features for modern devices. */
>                       features.features = (uint32_t)
> -                        (vdev->host_features & ~VIRTIO_LEGACY_FEATURES);
> +                        (vdev->host_features & ~vdc->legacy_features);
>                   } else {
>                       features.features = (uint32_t)vdev->host_features;
>                   }
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 62001b4..97b32fe 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1175,7 +1175,9 @@ static uint64_t virtio_pci_common_read(void *opaque, hwaddr addr,
>           break;
>       case VIRTIO_PCI_COMMON_DF:
>           if (proxy->dfselect <= 1) {
> -            val = (vdev->host_features & ~VIRTIO_LEGACY_FEATURES) >>
> +            VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
> +
> +            val = (vdev->host_features & ~vdc->legacy_features) >>
>                   (32 * proxy->dfselect);
>           }
>           break;
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 1df5f4e..72ee06b 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2214,6 +2214,8 @@ static void virtio_device_class_init(ObjectClass *klass, void *data)
>       dc->props = virtio_properties;
>       vdc->start_ioeventfd = virtio_device_start_ioeventfd_impl;
>       vdc->stop_ioeventfd = virtio_device_stop_ioeventfd_impl;
> +
> +    vdc->legacy_features |= VIRTIO_LEGACY_FEATURES;
>   }
>   
>   bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev)

Acked-by: Jason Wang <jasowang@redhat.com>