Re: [dpdk-dev] [PATCH] vhost: Fix default value of kickfd and callfd

[Tetsuya Mukawa <mukawa@igel.co.jp>]

On 2016/03/10 15:39, Tan, Jianfeng wrote:
>
> On 3/10/2016 2:34 PM, Tetsuya Mukawa wrote:
>> On 2016/03/10 15:25, Tan, Jianfeng wrote:
>>>
>>> On 3/10/2016 2:14 PM, Tetsuya Mukawa wrote:
>>>> Currently, default value of kickfd and callfd is -1.
>>>> If the value is -1, current code guess kickfd and callfd hasn't been
>>>> initialized yet. And vhost library will guess the virtqueue isn't
>>>> ready
>>>> for processing.
>>>> But callfd and kickfd will be set as -1 when "--enable-kvm"
>>>> isn't specified in QEMU command line. It means we cannot treat -1 as
>>>> uninitialized state. The patch changes default value to -2. And the
>>>> patch defines -2 as VIRTIO_UNINITIALIZED_EVENTFD.
>>>>
>>>> Signed-off-by: Tetsuya Mukawa <mukawa@igel.co.jp>
>>>> ---
>>>>    lib/librte_vhost/rte_virtio_net.h             | 1 +
>>>>    lib/librte_vhost/vhost_user/virtio-net-user.c | 7 ++++---
>>>>    lib/librte_vhost/virtio-net.c                 | 4 ++--
>>>>    3 files changed, 7 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/lib/librte_vhost/rte_virtio_net.h
>>>> b/lib/librte_vhost/rte_virtio_net.h
>>>> index 7d1fde2..d745707 100644
>>>> --- a/lib/librte_vhost/rte_virtio_net.h
>>>> +++ b/lib/librte_vhost/rte_virtio_net.h
>>>> @@ -89,6 +89,7 @@ struct vhost_virtqueue {
>>>>        uint16_t        vhost_hlen;        /**< Vhost header length
>>>> (varies depending on RX merge buffers. */
>>>>        volatile uint16_t    last_used_idx;        /**< Last index used
>>>> on the available ring */
>>>>        volatile uint16_t    last_used_idx_res;    /**< Used for
>>>> multiple devices reserving buffers. */
>>>> +#define VIRTIO_UNINITIALIZED_EVENTFD    (-2)
>>>>        int            callfd;            /**< Used to notify the guest
>>>> (trigger interrupt). */
>>>>        int            kickfd;            /**< Currently unused as
>>>> polling mode is enabled. */
>>>>        int            enabled;
>>>> diff --git a/lib/librte_vhost/vhost_user/virtio-net-user.c
>>>> b/lib/librte_vhost/vhost_user/virtio-net-user.c
>>>> index 65b5652..591f9bf 100644
>>>> --- a/lib/librte_vhost/vhost_user/virtio-net-user.c
>>>> +++ b/lib/librte_vhost/vhost_user/virtio-net-user.c
>>>> @@ -225,8 +225,8 @@ static int
>>>>    vq_is_ready(struct vhost_virtqueue *vq)
>>>>    {
>>>>        return vq && vq->desc   &&
>>>> -           vq->kickfd != -1 &&
>>>> -           vq->callfd != -1;
>>>> +           vq->kickfd != VIRTIO_UNINITIALIZED_EVENTFD &&
>>>> +           vq->callfd != VIRTIO_UNINITIALIZED_EVENTFD;
>>>>    }
>>>>      static int
>>>> @@ -318,7 +318,8 @@ user_get_vring_base(struct vhost_device_ctx ctx,
>>>>         */
>>>>        if (dev->virtqueue[state->index]->kickfd >= 0) {
>>>>            close(dev->virtqueue[state->index]->kickfd);
>>> Then -1 will be a valid value, need to check if it's not -1 to
>>> close()? Nevertheless, close(-1) brings no big problem.
>>>
>> We did it in above 'if' condition checking, then close(-1) will not be
>> called.
>
> Sorry, missed that. So when kickfd == -1, need to be set to
> VIRTIO_UNINITIALIZED_EVENTFD?
>

Aha, I've got it. Will change it.

Thanks,
Tetsuya

> Thanks,
> Jianfeng
>
>>
>> Thanks,
>> Tetsuya
>>
>>> Thanks,
>>> Jianfeng
>>>
>>>> -        dev->virtqueue[state->index]->kickfd = -1;
>>>> +        dev->virtqueue[state->index]->kickfd =
>>>> +                    VIRTIO_UNINITIALIZED_EVENTFD;
>>>>        }
>>>>          return 0;
>>>> diff --git a/lib/librte_vhost/virtio-net.c
>>>> b/lib/librte_vhost/virtio-net.c
>>>> index fe1a77e..3498e9d 100644
>>>> --- a/lib/librte_vhost/virtio-net.c
>>>> +++ b/lib/librte_vhost/virtio-net.c
>>>> @@ -263,8 +263,8 @@ init_vring_queue(struct vhost_virtqueue *vq, int
>>>> qp_idx)
>>>>    {
>>>>        memset(vq, 0, sizeof(struct vhost_virtqueue));
>>>>    -    vq->kickfd = -1;
>>>> -    vq->callfd = -1;
>>>> +    vq->kickfd = VIRTIO_UNINITIALIZED_EVENTFD;
>>>> +    vq->callfd = VIRTIO_UNINITIALIZED_EVENTFD;
>>>>          /* Backends are set to -1 indicating an inactive device. */
>>>>        vq->backend = -1;
>