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

Robin Murphy
2018-12-10T16:32:12Z

On 08/12/2018 20:01, Souptick Joarder wrote:
> Hi Robin,
>
> On Fri, Dec 7, 2018 at 12:07 AM Souptick Joarder <jrdr.linux@gmail.com> wrote:
>>
>> Convert to use vm_insert_range() to map range of kernel
>> memory to user vma.
>>
>> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
>> ---
>> 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
>>