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; } /* -- Catalin _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu