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

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Message-ID: <db93d5aa-64c4-42a4-73dc-ae25e9e3833e@redhat.com>
Date:   Fri, 29 Sep 2023 11:12:25 +0200
From:   Maxime Coquelin <maxime.coquelin@...hat.com>
To:     Jason Wang <jasowang@...hat.com>, Cindy Lu <lulu@...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 9/12/23 09:39, Jason Wang 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.
> 
> And I never saw _Bool is used in uapi before, maybe it's better to
> pack it with last_avail_idx into a __u32.

Better as two distincts __u16 IMHO.

Thanks,
Maxime

> 
> Btw, do we need to track inflight descriptors as well?
> 
> Thanks
> 
>> +};
>> +
>>   #endif /* _UAPI_VDUSE_H_ */
>> --
>> 2.34.3
>>
>