Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
MIME-Version: 1.0
References: <20230912030008.3599514-1-lulu@redhat.com> <20230912030008.3599514-3-lulu@redhat.com>
In-Reply-To: <20230912030008.3599514-3-lulu@redhat.com>
From:   Jason Wang <jasowang@redhat.com>
Date:   Mon, 18 Sep 2023 16:46:18 +0800
Message-ID: <CACGkMEuOYWYYGta5VoZaURVxrBFwU+1aNwoh7RyT1woQCNHJtg@mail.gmail.com>
Subject: Re: [RFC v2 2/4] vduse: Add file operation for mmap
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 11:00=E2=80=AFAM Cindy Lu <lulu@redhat.com> wrote:
>
> Add the operation for mmap, The user space APP will
> use this function to map the pages to userspace
>
> Signed-off-by: Cindy Lu <lulu@redhat.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 63 ++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/=
vduse_dev.c
> index 4c256fa31fc4..2c69f4004a6e 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1388,6 +1388,67 @@ static struct vduse_dev *vduse_dev_get_from_minor(=
int minor)
>         return dev;
>  }
>
> +static vm_fault_t vduse_vm_fault(struct vm_fault *vmf)
> +{
> +       struct vduse_dev *dev =3D vmf->vma->vm_file->private_data;
> +       struct vm_area_struct *vma =3D vmf->vma;
> +       u16 index =3D vma->vm_pgoff;
> +       struct vduse_virtqueue *vq;
> +       struct vdpa_reconnect_info *info;
> +
> +       if (index =3D=3D 0) {
> +               info =3D &dev->reconnect_status;
> +       } else {
> +               vq =3D &dev->vqs[index - 1];
> +               info =3D &vq->reconnect_info;
> +       }
> +       vma->vm_page_prot =3D pgprot_noncached(vma->vm_page_prot);
> +       if (remap_pfn_range(vma, vmf->address & PAGE_MASK, PFN_DOWN(info-=
>addr),
> +                           PAGE_SIZE, vma->vm_page_prot))
> +               return VM_FAULT_SIGBUS;
> +       return VM_FAULT_NOPAGE;
> +}
> +
> +static const struct vm_operations_struct vduse_vm_ops =3D {
> +       .fault =3D vduse_vm_fault,
> +};
> +
> +static int vduse_dev_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> +       struct vduse_dev *dev =3D file->private_data;
> +       struct vdpa_reconnect_info *info;
> +       unsigned long index =3D vma->vm_pgoff;
> +       struct vduse_virtqueue *vq;
> +
> +       if (vma->vm_end - vma->vm_start !=3D PAGE_SIZE)
> +               return -EINVAL;
> +       if ((vma->vm_flags & VM_SHARED) =3D=3D 0)
> +               return -EINVAL;
> +
> +       if (index > 65535)
> +               return -EINVAL;
> +
> +       if (index =3D=3D 0) {
> +               info =3D &dev->reconnect_status;
> +       } else {
> +               vq =3D &dev->vqs[index - 1];
> +               info =3D &vq->reconnect_info;
> +       }
> +
> +       if (info->index !=3D index)
> +               return -EINVAL;

Under which case could we meet this?

> +
> +       if (info->addr & (PAGE_SIZE - 1))
> +               return -EINVAL;

And this?

> +       if (vma->vm_end - vma->vm_start !=3D info->size)
> +               return -EOPNOTSUPP;
> +
> +       vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTDUMP);

Why do you use VM_IO, VM_PFNMAP and VM_DONTDUMP?

Thanks

> +       vma->vm_ops =3D &vduse_vm_ops;
> +
> +       return 0;
> +}
> +
>  static int vduse_dev_open(struct inode *inode, struct file *file)
>  {
>         int ret;
> @@ -1420,6 +1481,8 @@ static const struct file_operations vduse_dev_fops =
=3D {
>         .unlocked_ioctl =3D vduse_dev_ioctl,
>         .compat_ioctl   =3D compat_ptr_ioctl,
>         .llseek         =3D noop_llseek,
> +       .mmap           =3D vduse_dev_mmap,
> +
>  };
>
>  static struct vduse_dev *vduse_dev_create(void)
> --
> 2.34.3
>