On 04/21/2017 09:12 AM, Catalin Marinas wrote:
> On Wed, Mar 29, 2017 at 01:55:32PM +0100, Robin Murphy wrote:
>> On 29/03/17 11:05, Andrzej Hajda wrote:
>>> In case of DMA_ATTR_FORCE_CONTIGUOUS allocations vm_area->pages
>>> is invalid. __iommu_mmap_attrs and __iommu_get_sgtable cannot use
>>> it. In first case temporary pages array is passed to iommu_dma_mmap,
>>> in 2nd case single entry sg table is created directly instead
>>> of calling helper.
>>>
>>> Fixes: 44176bb ("arm64: Add support for DMA_ATTR_FORCE_CONTIGUOUS to IOMMU")
>>> Signed-off-by: Andrzej Hajda <a.ha...@samsung.com>
>>> ---
>>> Hi,
>>>
>>> I am not familiar with this framework so please don't be too cruel ;)
>>> Alternative solution I see is to always create vm_area->pages,
>>> I do not know which approach is preferred.
>>>
>>> Regards
>>> Andrzej
>>> ---
>>> arch/arm64/mm/dma-mapping.c | 40 ++++++++++++++++++++++++++++++++++++++--
>>> 1 file changed, 38 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
>>> index f7b5401..bba2bc8 100644
>>> --- a/arch/arm64/mm/dma-mapping.c
>>> +++ b/arch/arm64/mm/dma-mapping.c
>>> @@ -704,7 +704,30 @@ static int __iommu_mmap_attrs(struct device *dev,
>>> struct vm_area_struct *vma,
>>> return ret;
>>>
>>> area = find_vm_area(cpu_addr);
>>> - if (WARN_ON(!area || !area->pages))
>>> + if (WARN_ON(!area))
>>
>> From the look of things, it doesn't seem strictly necessary to change
>> this, but whether that's a good thing is another matter. I'm not sure
>> that dma_common_contiguous_remap() should really be leaving a dangling
>> pointer in area->pages as it apparently does... :/
>
> On this specific point, I don't think area->pages should be set either
> (cc'ing Laura). As in the vmalloc vs vmap case, area->pages when pages
> need to be freed (via vfree), which is not the case here. The
> dma_common_pages_remap() would need to set area->pages when called
> directly from the iommu DMA ops. Proposal below, not tested with the
> iommu ops. I assume the patch would cause __iommu_mmap_attrs() to return
> -ENXIO if DMA_ATTR_FORCE_CONTIGUOUS is set.
>
> ------------8<---------------------------------
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index efd71cf4fdea..ab7071041141 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -277,8 +277,8 @@ EXPORT_SYMBOL(dma_common_mmap);
> * remaps an array of PAGE_SIZE pages into another vm_area
> * Cannot be used in non-sleeping contexts
> */
> -void *dma_common_pages_remap(struct page **pages, size_t size,
> - unsigned long vm_flags, pgprot_t prot,
> +static struct vm_struct *__dma_common_pages_remap(struct page **pages,
> + size_t size, unsigned long vm_flags, pgprot_t prot,
> const void *caller)
> {
> struct vm_struct *area;
> @@ -287,13 +287,26 @@ void *dma_common_pages_remap(struct page **pages,
> size_t size,
> if (!area)
> return NULL;
>
> - area->pages = pages;
> -
> if (map_vm_area(area, prot, pages)) {
> vunmap(area->addr);
> return NULL;
> }
>
> + return area;
> +}
> +
> +void *dma_common_pages_remap(struct page **pages, size_t size,
> + unsigned long vm_flags, pgprot_t prot,
> + const void *caller)
> +{
> + struct vm_struct *area;
> +
> + area = __dma_common_pages_remap(pages, size, vm_flags, prot, caller);
> + if (!area)
> + return NULL;
> +
> + area->pages = pages;
> +
> return area->addr;
> }
>
> @@ -308,7 +321,7 @@ void *dma_common_contiguous_remap(struct page *page,
> size_t size,
> {
> int i;
> struct page **pages;
> - void *ptr;
> + struct vm_struct *area;
> unsigned long pfn;
>
> pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL);
> @@ -318,11 +331,13 @@ void *dma_common_contiguous_remap(struct page *page,
> size_t size,
> for (i = 0, pfn = page_to_pfn(page); i < (size >> PAGE_SHIFT); i++)
> pages[i] = pfn_to_page(pfn + i);
>
> - ptr = dma_common_pages_remap(pages, size, vm_flags, prot, caller);
> + area = __dma_common_pages_remap(pages, size, vm_flags, prot, caller);
>
> kfree(pages);
>
> - return ptr;
> + if (!area)
> + return NULL;
> + return area->addr;
> }
>
> /*
>
>From a quick glance, this looks okay. I can give a proper tag when
the fix to allow mmaping comes in since I'm guessing -ENXIO is not the
end goal.
Thanks,
Laura
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
