linux-kernel - Re: [RFC v2 3/4] vduse: update the vq

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Message-ID: <0af14066-6cc9-bfc6-2a4c-0503f9dd4a5c@redhat.com>
Date:   Fri, 29 Sep 2023 11:08:02 +0200
From:   Maxime Coquelin <maxime.coquelin@...hat.com>
To:     Cindy Lu <lulu@...hat.com>, Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, xieyongji@...edance.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [RFC v2 3/4] vduse: update the vq_info in ioctl



On 9/25/23 06:15, Cindy Lu wrote:
> On Tue, Sep 12, 2023 at 3:39 PM Jason Wang <jasowang@...hat.com> wrote:
>>
>> On Tue, Sep 12, 2023 at 11:00 AM Cindy Lu <lulu@...hat.com> wrote:
>>>
>>> In VDUSE_VQ_GET_INFO, the driver will sync the last_avail_idx
>>> with reconnect info, After mapping the reconnect pages to userspace
>>> The userspace App will update the reconnect_time in
>>> struct vhost_reconnect_vring, If this is not 0 then it means this
>>> vq is reconnected and will update the last_avail_idx
>>>
>>> Signed-off-by: Cindy Lu <lulu@...hat.com>
>>> ---
>>>   drivers/vdpa/vdpa_user/vduse_dev.c | 13 +++++++++++++
>>>   include/uapi/linux/vduse.h         |  6 ++++++
>>>   2 files changed, 19 insertions(+)
>>>
>>> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
>>> index 2c69f4004a6e..680b23dbdde2 100644
>>> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
>>> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>>> @@ -1221,6 +1221,8 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
>>>                  struct vduse_vq_info vq_info;
>>>                  struct vduse_virtqueue *vq;
>>>                  u32 index;
>>> +               struct vdpa_reconnect_info *area;
>>> +               struct vhost_reconnect_vring *vq_reconnect;
>>>
>>>                  ret = -EFAULT;
>>>                  if (copy_from_user(&vq_info, argp, sizeof(vq_info)))
>>> @@ -1252,6 +1254,17 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
>>>
>>>                  vq_info.ready = vq->ready;
>>>
>>> +               area = &vq->reconnect_info;
>>> +
>>> +               vq_reconnect = (struct vhost_reconnect_vring *)area->vaddr;
>>> +               /*check if the vq is reconnect, if yes then update the last_avail_idx*/
>>> +               if ((vq_reconnect->last_avail_idx !=
>>> +                    vq_info.split.avail_index) &&
>>> +                   (vq_reconnect->reconnect_time != 0)) {
>>> +                       vq_info.split.avail_index =
>>> +                               vq_reconnect->last_avail_idx;
>>> +               }
>>> +
>>>                  ret = -EFAULT;
>>>                  if (copy_to_user(argp, &vq_info, sizeof(vq_info)))
>>>                          break;
>>> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
>>> index 11bd48c72c6c..d585425803fd 100644
>>> --- a/include/uapi/linux/vduse.h
>>> +++ b/include/uapi/linux/vduse.h
>>> @@ -350,4 +350,10 @@ struct vduse_dev_response {
>>>          };
>>>   };
>>>
>>> +struct vhost_reconnect_vring {
>>> +       __u16 reconnect_time;
>>> +       __u16 last_avail_idx;
>>> +       _Bool avail_wrap_counter;
>>
>> Please add a comment for each field.
>>
> Sure will do
> 
>> And I never saw _Bool is used in uapi before, maybe it's better to
>> pack it with last_avail_idx into a __u32.
>>
> Thanks will fix this
>> Btw, do we need to track inflight descriptors as well?
>>
> I will check this

For existing networking implemenation, this is not necessary.
But it should be for block devices.

Maxime

> Thanks
> 
> cindy
>> Thanks
>>
>>> +};
>>> +
>>>   #endif /* _UAPI_VDUSE_H_ */
>>> --
>>> 2.34.3
>>>
>>
>