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

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

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.

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;
>