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    SubjectRe: [PATCH v5] vhost: introduce mdev based hardware backend
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    On 2019/11/6 下午10:49, Tiwei Bie wrote:
    >>>>>> + default:
    >>>>>> + /*
    >>>>>> + * VHOST_SET_MEM_TABLE, VHOST_SET_LOG_BASE, and
    >>>>>> + * VHOST_SET_LOG_FD are not used yet.
    >>>>>> + */
    >>>>> If we don't even use them, there's probably no need to call
    >>>>> vhost_dev_ioctl(). This may help to avoid confusion when we want to develop
    >>>>> new API for e.g dirty page tracking.
    >>>> Good point. It's better to reject these ioctls for now.
    >>>>
    >>>> PS. One thing I may need to clarify is that, we need the
    >>>> VHOST_SET_OWNER ioctl to get the vq->handle_kick to work.
    >>>> So if we don't call vhost_dev_ioctl(), we will need to
    >>>> call vhost_dev_set_owner() directly.
    >> I may miss something, it looks to me the there's no owner check in
    >> vhost_vring_ioctl() and the vhost_poll_start() can make sure handle_kick
    >> works?
    > Yeah, there is no owner check in vhost_vring_ioctl().
    > IIUC, vhost_poll_start() will start polling the file. And when
    > event arrives, vhost_poll_wakeup() will be called, and it will
    > queue work to work_list and wakeup worker to finish the work.
    > And the worker is created by vhost_dev_set_owner().
    >

    Right, rethink about this. It looks to me we need:

    - Keep VHOST_SET_OWNER, this could be used for future control vq where
    it needs a kthread to access the userspace memory

    - Temporarily filter  SET_LOG_BASE and SET_LOG_FD until we finalize the
    API for dirty page tracking.

    - For kick through kthread, it looks sub-optimal but we can address this
    in the future, e.g call handle_vq_kick directly in vhost_poll_queue
    (probably a flag for vhost_poll) and deal with the synchronization in
    vhost_poll_flush carefully.

    Thanks


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