On Fri, Aug 08, 2014 at 11:45:56PM +0100, Andrew Morton wrote: > On Fri, 8 Aug 2014 13:23:15 -0700 Laura Abbott <[email protected]> wrote: > > For architectures without coherent DMA, memory for DMA may > > need to be remapped with coherent attributes. Factor out > > the the remapping code from arm and put it in a > > common location to reduce code duplication. > > > > As part of this, the arm APIs are now migrated away from > > ioremap_page_range to the common APIs which use map_vm_area for remapping. > > This should be an equivalent change and using map_vm_area is more > > correct as ioremap_page_range is intended to bring in io addresses > > into the cpu space and not regular kernel managed memory. > > > > ... > > > > @@ -267,3 +269,68 @@ int dma_common_mmap(struct device *dev, struct > > vm_area_struct *vma, > > return ret; > > } > > EXPORT_SYMBOL(dma_common_mmap); > > + > > +/* > > + * remaps an allocated contiguous region into another vm_area. > > + * Cannot be used in non-sleeping contexts > > + */ > > + > > +void *dma_common_contiguous_remap(struct page *page, size_t size, > > + unsigned long vm_flags, > > + pgprot_t prot, const void *caller) > > +{ > > + int i; > > + struct page **pages; > > + void *ptr; > > + > > + pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL); > > + if (!pages) > > + return NULL; > > + > > + for (i = 0; i < (size >> PAGE_SHIFT); i++) > > + pages[i] = page + i; > > Assumes a single mem_map[] array. That's not the case for sparsemem > (at least).
Good point. The "page" pointer (and memory range) passed to this function has been allocated with alloc_pages(), so the range is guaranteed to be physically contiguous but it does not imply a single mem_map[] array. For arm64 with SPARSEMEM_VMEMMAP_ENABLE it's safe but not all architectures use this (especially on 32-bit). What about using pfn_to_page(pfn + i)? Thanks. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
