linux-kernel - Re: [PATCH v2 2/5] vduse: Add file operation for mmap

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Message-ID: <CACLfguX-b4JCAKoD0FHjRRj6Kh13LzW2Z4HK5t-bXqczLBJBbg@mail.gmail.com>
Date:   Sat, 25 Nov 2023 21:46:21 +0800
From:   Cindy Lu <lulu@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, xieyongji@...edance.com,
        linux-kernel@...r.kernel.org, maxime.coquelin@...hat.com
Subject: Re: [PATCH v2 2/5] vduse: Add file operation for mmap

On Wed, Nov 22, 2023 at 2:14 PM Jason Wang <jasowang@...hat.com> wrote:
>
> On Tue, Nov 21, 2023 at 3:31 PM Cindy Lu <lulu@...hat.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@...hat.com>
> > ---
> >  drivers/vdpa/vdpa_user/vduse_dev.c | 79 ++++++++++++++++++++++++++++++
> >  1 file changed, 79 insertions(+)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index 6209e2f00278..ccb30e98bab5 100644
> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -1376,6 +1376,83 @@ 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 = vmf->vma->vm_file->private_data;
> > +       struct vm_area_struct *vma = vmf->vma;
> > +       u16 index = vma->vm_pgoff;
> > +       struct vduse_virtqueue *vq;
> > +       struct vdpa_reconnect_info *info;
> > +
> > +       /* index 0  page reserved for vduse status*/
> > +       if (index == 0) {
>
> I'd avoid using magic numbers but a well defined uAPI for 0.
>
sure will Add this

> > +               info = &dev->reconnect_info;
> > +       } else {
> > +               /* index 1+vq_number page reserved for vduse vqs*/
> > +               vq = &dev->vqs[index - 1];
> > +               info = &vq->reconnect_info;
> > +       }
> > +       if (remap_pfn_range(vma, vmf->address & PAGE_MASK,
> > +                           PFN_DOWN(virt_to_phys((void *)info->vaddr)),
> > +                           PAGE_SIZE, vma->vm_page_prot))
> > +               return VM_FAULT_SIGBUS;
> > +       return VM_FAULT_NOPAGE;
> > +}
> > +
> > +static const struct vm_operations_struct vduse_vm_ops = {
> > +       .fault = vduse_vm_fault,
> > +};
> > +
> > +static int vduse_dev_mmap(struct file *file, struct vm_area_struct *vma)
> > +{
> > +       struct vduse_dev *dev = file->private_data;
> > +       struct vdpa_reconnect_info *info;
> > +       unsigned long index = vma->vm_pgoff;
> > +       struct vduse_virtqueue *vq;
> > +
> > +       if (vma->vm_end - vma->vm_start != PAGE_SIZE)
> > +               return -EINVAL;
> > +       if ((vma->vm_flags & VM_SHARED) == 0)
> > +               return -EINVAL;
> > +
> > +       /*check if Userspace App map the page number larger than kernel allocated*/
>
> Code explains themselves, such comment is not necessary.
>
sure will remove this
> > +       if (index > dev->vq_num + 1)
> > +               return -EINVAL;
> > +
> > +       /* index 0  page reserved for vduse status*/
> > +       if (index == 0) {
> > +               info = &dev->reconnect_info;
> > +       } else {
> > +               /* index 1+vq_number page reserved for vduse vqs*/
> > +               vq = &dev->vqs[index - 1];
> > +               info = &vq->reconnect_info;
> > +       }
> > +       /*check if map pages was allocated and inited by kernel */
>
> Typo above.
>
> > +       if (info->vaddr == 0)
> > +               return -EOPNOTSUPP;
>
> Under which condition can we reach here?
>
if the userApp call this mmap without call the dev_create,may
cause this problem, So Add the check here
thanks
Cindy
> > +
> > +       /* check if the address is page aligned, if not,
> > +        * this address maybe damaged
> > +        */
> > +       if (virt_to_phys((void *)info->vaddr) & (PAGE_SIZE - 1))
> > +               return -EINVAL;
>
> And here?
>
if the address is not page-aligned, this information may be damaged
So add the check here
> Thanks
>
> > +
> > +       /* check if Userspace App mapped the correct size
> > +        * the userspace App should map one page each time
> > +        */
> > +       if (vma->vm_end - vma->vm_start != PAGE_SIZE)
> > +               return -EOPNOTSUPP;
> > +       /* VM_IO: set as a memory-mapped I/O region,This will for vq information
> > +        * VM_PFNMAP: only need  the pure PFN
> > +        * VM_DONTEXPAND: do not need to use mremap() in this function
> > +        * VM_DONTDUMP:Do not include in the core dump
> > +        */
> > +       vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
> > +       vma->vm_ops = &vduse_vm_ops;
> > +
> > +       return 0;
> > +}
> > +
> >  static int vduse_dev_open(struct inode *inode, struct file *file)
> >  {
> >         int ret;
> > @@ -1408,6 +1485,8 @@ static const struct file_operations vduse_dev_fops = {
> >         .unlocked_ioctl = vduse_dev_ioctl,
> >         .compat_ioctl   = compat_ptr_ioctl,
> >         .llseek         = noop_llseek,
> > +       .mmap           = vduse_dev_mmap,
> > +
> >  };
> >
> >  static struct vduse_dev *vduse_dev_create(void)
> > --
> > 2.34.3
> >
>