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

From: Robin Murphy
Date: Mon Dec 10 2018 - 11:32:15 EST


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