Re: [PATCH v3 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range

[Robin Murphy]

On 08/12/2018 20:01, Souptick Joarder wrote:
> Hi Robin,
>
> On Fri, Dec 7, 2018 at 12:07 AM Souptick Joarder <jrdr.linux@xxxxxxxxx> wrote:
> > Convert to use vm_insert_range() to map range of kernel
> > memory to user vma.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> > ---
> >   arch/arm/mm/dma-mapping.c | 21 +++++++--------------
> >   1 file changed, 7 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> > index 661fe48..4eec323 100644
> > --- a/arch/arm/mm/dma-mapping.c
> > +++ b/arch/arm/mm/dma-mapping.c
> > @@ -1582,31 +1582,24 @@ static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma
> >                      void *cpu_addr, dma_addr_t dma_addr, size_t size,
> >                      unsigned long attrs)
> >   {
> > -       unsigned long uaddr = vma->vm_start;
> > -       unsigned long usize = vma->vm_end - vma->vm_start;
> > +       unsigned long page_count = vma_pages(vma);
> >          struct page **pages = __iommu_get_pages(cpu_addr, attrs);
> >          unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> >          unsigned long off = vma->vm_pgoff;
> > +       int err;
> >
> >          if (!pages)
> >                  return -ENXIO;
> >
> > -       if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off)
> > +       if (off >= nr_pages || page_count > nr_pages - off)
> >                  return -ENXIO;
> >
> >          pages += off;
> > +       err = vm_insert_range(vma, vma->vm_start, pages, page_count);
>
> Just to clarify, do we need to adjust page_count with vma->vm_pgoff as
> original code
> have not consider it and run the loop for entire range irrespective of
> vma->vm_pgoff value ?

In this instance, page_count is the size of the VMA, not the size of the 
pages array itself, so as I understand things this patch is true to the 
original code as-is.

Robin.

> > +       if (err)
> > +               pr_err("Remapping memory failed: %d\n", err);
> >
> > -       do {
> > -               int ret = vm_insert_page(vma, uaddr, *pages++);
> > -               if (ret) {
> > -                       pr_err("Remapping memory failed: %d\n", ret);
> > -                       return ret;
> > -               }
> > -               uaddr += PAGE_SIZE;
> > -               usize -= PAGE_SIZE;
> > -       } while (usize > 0);
> > -
> > -       return 0;
> > +       return err;
> >   }
> >   static int arm_iommu_mmap_attrs(struct device *dev,
> >                  struct vm_area_struct *vma, void *cpu_addr,
> > --
> > 1.9.1