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SubjectRe: [PATCH v3 4/9] drm/rockchip/rockchip_drm_gem.c: Convert to use vm_insert_range
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On 2018-12-07 8:30 pm, Souptick Joarder wrote:
> On Fri, Dec 7, 2018 at 8:20 PM Robin Murphy <robin.murphy@arm.com> wrote:
>>
>> On 06/12/2018 18:42, Souptick Joarder 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>
>>> Tested-by: Heiko Stuebner <heiko@sntech.de>
>>> Acked-by: Heiko Stuebner <heiko@sntech.de>
>>> ---
>>> drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 20 ++------------------
>>> 1 file changed, 2 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
>>> index a8db758..2cb83bb 100644
>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
>>> @@ -221,26 +221,10 @@ static int rockchip_drm_gem_object_mmap_iommu(struct drm_gem_object *obj,
>>> struct vm_area_struct *vma)
>>> {
>>> struct rockchip_gem_object *rk_obj = to_rockchip_obj(obj);
>>> - unsigned int i, count = obj->size >> PAGE_SHIFT;
>>> unsigned long user_count = vma_pages(vma);
>>> - unsigned long uaddr = vma->vm_start;
>>> - unsigned long offset = vma->vm_pgoff;
>>> - unsigned long end = user_count + offset;
>>> - int ret;
>>> -
>>> - if (user_count == 0)
>>> - return -ENXIO;
>>> - if (end > count)
>>> - return -ENXIO;
>>>
>>> - for (i = offset; i < end; i++) {
>>> - ret = vm_insert_page(vma, uaddr, rk_obj->pages[i]);
>>> - if (ret)
>>> - return ret;
>>> - uaddr += PAGE_SIZE;
>>> - }
>>> -
>>> - return 0;
>>> + return vm_insert_range(vma, vma->vm_start, rk_obj->pages,
>>> + user_count);
>>
>> We're losing vm_pgoff handling here, which given the implication in
>> 57de50af162b, may well be a regression for at least some combination of
>> GPU and userspace driver (I assume that commit was in the context of
>> some version of the Arm Mali driver, possibly on RK3288).
>
> In commit 57de50af162b, vma->vm_pgoff = 0 for GEM mmap handler context
> and removing it from common path which means if call stack looks like
> rockchip_gem_mmap_buf() -> rockchip_drm_gem_object_mmap() ->
> rockchip_drm_gem_object_mmap_iommu(), then we might have a non zero
> vma->vm_pgoff context which is not handled.
>
> This is the problem you are pointing ? right ?

Exactly - if unconditionally zeroing the offset in the PRIME mmap() path
was a problem, then the implication is that there are callers of that
path who expect the offset to be honoured here.

Robin.

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