Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33;
MIME-Version: 1.0
References: <20230912030008.3599514-1-lulu@redhat.com> <20230912030008.3599514-5-lulu@redhat.com>
In-Reply-To: <20230912030008.3599514-5-lulu@redhat.com>
From:   Jason Wang <jasowang@redhat.com>
Date:   Mon, 18 Sep 2023 16:48:49 +0800
Message-ID: <CACGkMEtCYG8-Pt+V-OOwUV7fYFp_cnxU68Moisfxju9veJ-=qw@mail.gmail.com>
Subject: Re: [RFC v2 4/4] vduse: Add new ioctl VDUSE_GET_RECONNECT_INFO
To:     Cindy Lu <lulu@redhat.com>
Cc:     mst@redhat.com, maxime.coquelin@redhat.com,
        xieyongji@bytedance.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        stable@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tue, Sep 12, 2023 at 11:01=E2=80=AFAM Cindy Lu <lulu@redhat.com> wrote:
>
> In VDUSE_GET_RECONNECT_INFO, the Userspace App can get the map size
> and The number of mapping memory pages from the kernel. The userspace
> App can use this information to map the pages.
>
> Signed-off-by: Cindy Lu <lulu@redhat.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 15 +++++++++++++++
>  include/uapi/linux/vduse.h         | 15 +++++++++++++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/=
vduse_dev.c
> index 680b23dbdde2..c99f99892b5c 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1368,6 +1368,21 @@ static long vduse_dev_ioctl(struct file *file, uns=
igned int cmd,
>                 ret =3D 0;
>                 break;
>         }
> +       case VDUSE_GET_RECONNECT_INFO: {
> +               struct vduse_reconnect_mmap_info info;
> +
> +               ret =3D -EFAULT;
> +               if (copy_from_user(&info, argp, sizeof(info)))
> +                       break;
> +
> +               info.size =3D PAGE_SIZE;
> +               info.max_index =3D dev->vq_num + 1;
> +
> +               if (copy_to_user(argp, &info, sizeof(info)))
> +                       break;
> +               ret =3D 0;
> +               break;
> +       }
>         default:
>                 ret =3D -ENOIOCTLCMD;
>                 break;
> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> index d585425803fd..ce55e34f63d7 100644
> --- a/include/uapi/linux/vduse.h
> +++ b/include/uapi/linux/vduse.h
> @@ -356,4 +356,19 @@ struct vhost_reconnect_vring {
>         _Bool avail_wrap_counter;
>  };
>
> +/**
> + * struct vduse_reconnect_mmap_info
> + * @size: mapping memory size, always page_size here
> + * @max_index: the number of pages allocated in kernel,just
> + * use for check
> + */
> +
> +struct vduse_reconnect_mmap_info {
> +       __u32 size;
> +       __u32 max_index;
> +};

One thing I didn't understand is that, aren't the things we used to
store connection info belong to uAPI? If not, how can we make sure the
connections work across different vendors/implementations. If yes,
where?

Thanks

> +
> +#define VDUSE_GET_RECONNECT_INFO \
> +       _IOWR(VDUSE_BASE, 0x1b, struct vduse_reconnect_mmap_info)
> +
>  #endif /* _UAPI_VDUSE_H_ */
> --
> 2.34.3
>