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    SubjectRe: [PATCH 2/2] ARM: DMA: Use vm_pgoff for IOMMU mmap
    Hi Ørjan,

    On Thu, Apr 16, 2015 at 10:41 PM, Ørjan Eide <orjan.eide@arm.com> wrote:
    > arm_iommu_mmap_attrs() ignores the page offset in vma->vm_pgoff that was
    > specified in the mmap call. Any user of dma_mmap_* will get an
    > unexpected result when the device uses the IOMMU DMA ops.
    >
    > Some DRM driver that use dma_mmap_* seems to depend on it ignoring
    > vma->vm_pgoff. Both the Samsung Exynos DRM driver before v3.18, and the
    > current Rockchip DRM driver, use the page offset to pass GEM cookies
    > that are used to look up the GEM buffers and then call dma_mmap_attrs()
    > with the cookie value still in vma->vm_pgoff.
    >
    > rockchip_gem_mmap_buf() in drivers/gpu/drm/rockchip/rockchip_drm_gem.c
    > still does this. It should be fixed before fixing
    > arm_iommu_mmap_attrs().
    >
    > Signed-off-by: Ørjan Eide <orjan.eide@arm.com>

    Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>

    I tested this patch on my RK3288 board with the corresponding
    rockchip_drm patch [0], and it works. So, also:
    Tested-by: Daniel Kurtz <djkurtz@chromium.org>

    [0] https://patchwork.kernel.org/patch/6226591/



    > ---
    > arch/arm/mm/dma-mapping.c | 8 ++++++++
    > 1 file changed, 8 insertions(+)
    >
    > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
    > index c274476..07d571b 100644
    > --- a/arch/arm/mm/dma-mapping.c
    > +++ b/arch/arm/mm/dma-mapping.c
    > @@ -1364,6 +1364,9 @@ static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
    > {
    > unsigned long uaddr = vma->vm_start;
    > unsigned long usize = vma->vm_end - vma->vm_start;
    > + unsigned long nr_vma_pages = usize >> PAGE_SHIFT;
    > + unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
    > + unsigned long off = vma->vm_pgoff;
    > struct page **pages = __iommu_get_pages(cpu_addr, attrs);
    >
    > vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
    > @@ -1371,6 +1374,11 @@ static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
    > if (!pages)
    > return -ENXIO;
    >
    > + if (off >= nr_pages || nr_vma_pages > (nr_pages - off))
    > + return -ENXIO;
    > +
    > + pages += off;
    > +
    > do {
    > int ret = vm_insert_page(vma, uaddr, *pages++);
    > if (ret) {
    > --
    > 1.9.1
    >


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