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

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Message-ID: <CACGkMEsNfLOQkmnWUH53iTptAmhELs_U8B4D-CfO49rs=+HfLw@mail.gmail.com>
Date:   Sun, 8 Oct 2023 13:17:23 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Maxime Coquelin <maxime.coquelin@...hat.com>
Cc:     Cindy Lu <lulu@...hat.com>, 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 Fri, Sep 29, 2023 at 5:12 PM Maxime Coquelin
<maxime.coquelin@...hat.com> wrote:
>
>
>
> 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.

Fine with me.

Thanks

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