On 11/04/2015 05:11 AM, Robin Murphy wrote:
On 04/11/15 08:39, Yong Wu wrote:On Thu, 2015-10-01 at 20:13 +0100, Robin Murphy wrote:Taking some inspiration from the arch/arm code, implement the arch-specific side of the DMA mapping ops using the new IOMMU-DMA layer.[...]+static void *__iommu_alloc_attrs(struct device *dev, size_t size, + dma_addr_t *handle, gfp_t gfp, + struct dma_attrs *attrs) +{ + bool coherent = is_device_dma_coherent(dev); + int ioprot = dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent); + void *addr; + + if (WARN(!dev, "cannot create IOMMU mapping for unknown device\n")) + return NULL; + /* + * Some drivers rely on this, and we probably don't want the + * possibility of stale kernel data being read by devices anyway. + */ + gfp |= __GFP_ZERO; + + if (gfp & __GFP_WAIT) { + struct page **pages; + pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL, coherent); + + pages = iommu_dma_alloc(dev, size, gfp, ioprot, handle, + flush_page); + if (!pages) + return NULL; + + addr = dma_common_pages_remap(pages, size, VM_USERMAP, prot, + __builtin_return_address(0)); + if (!addr) + iommu_dma_free(dev, pages, size, handle); + } else { + struct page *page; + /* + * In atomic context we can't remap anything, so we'll only + * get the virtually contiguous buffer we need by way of a + * physically contiguous allocation. + */ + if (coherent) { + page = alloc_pages(gfp, get_order(size)); + addr = page ? page_address(page) : NULL; + } else { + addr = __alloc_from_pool(size, &page, gfp); + } + if (!addr) + return NULL; + + *handle = iommu_dma_map_page(dev, page, 0, size, ioprot); + if (iommu_dma_mapping_error(dev, *handle)) { + if (coherent) + __free_pages(page, get_order(size)); + else + __free_from_pool(addr, size); + addr = NULL; + } + } + return addr; +} + +static void __iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr, + dma_addr_t handle, struct dma_attrs *attrs) +{ + /* + * @cpu_addr will be one of 3 things depending on how it was allocated: + * - A remapped array of pages from iommu_dma_alloc(), for all + * non-atomic allocations. + * - A non-cacheable alias from the atomic pool, for atomic + * allocations by non-coherent devices. + * - A normal lowmem address, for atomic allocations by + * coherent devices. + * Hence how dodgy the below logic looks... + */ + if (__in_atomic_pool(cpu_addr, size)) { + iommu_dma_unmap_page(dev, handle, size, 0, NULL); + __free_from_pool(cpu_addr, size); + } else if (is_vmalloc_addr(cpu_addr)){ + struct vm_struct *area = find_vm_area(cpu_addr); + + if (WARN_ON(!area || !area->pages)) + return; + iommu_dma_free(dev, area->pages, size, &handle); + dma_common_free_remap(cpu_addr, size, VM_USERMAP);Hi Robin, We get a WARN issue while the size is not aligned here. The WARN log is: [ 206.852002] WARNING: CPU: 0 PID: 23329 at /mnt/host/source/src/third_party/kernel/v3.18/mm/vmalloc.c:65 vunmap_page_range+0x190/0x1b4() [ 206.864438] Modules linked in: nls_iso8859_1 nls_cp437 vfat fat rfcomm i2c_dev uinput dm9601 uvcvideo btmrvl_sdio mwifiex_sdio mwifiex btmrvl bluetooth zram fuse cfg80211 nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables cdc_ether usbnet mii joydev snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device ppp_async ppp_generic slhc tun [ 206.902983] CPU: 0 PID: 23329 Comm: chrome Not tainted 3.18.0 #17 [ 206.910430] Hardware name: Mediatek Oak rev3 board (DT) [ 206.920018] Call trace: [ 206.925537] [<ffffffc000208c00>] dump_backtrace+0x0/0x140 [ 206.931905] [<ffffffc000208d5c>] show_stack+0x1c/0x28 [ 206.939158] [<ffffffc000870f80>] dump_stack+0x74/0x94 [ 206.947459] [<ffffffc0002219a4>] warn_slowpath_common+0x90/0xb8 [ 206.954100] [<ffffffc000221b58>] warn_slowpath_null+0x34/0x44 [ 206.961537] [<ffffffc000321358>] vunmap_page_range+0x18c/0x1b4 [ 206.967630] [<ffffffc0003213e4>] unmap_kernel_range+0x2c/0x78 [ 206.976977] [<ffffffc000582224>] dma_common_free_remap+0x68/0x80 [ 206.983581] [<ffffffc000217260>] __iommu_free_attrs+0x14c/0x160 [ 206.989646] [<ffffffc00066fc1c>] mtk_vcodec_mem_free+0xa0/0x15c [ 206.996481] [<ffffffc00067e278>] vp9_free_work_buf+0x54/0x70 [ 207.002260] [<ffffffc00067f168>] vdec_vp9_deinit+0x7c/0xe8 [ 207.008134] [<ffffffc0006787d8>] vdec_if_deinit+0x84/0xec [ 207.013820] [<ffffffc000677898>] mtk_vcodec_vdec_release+0x54/0x6c [ 207.020672] [<ffffffc000673e3c>] fops_vcodec_release+0x7c/0xf8 [ 207.026607] [<ffffffc000652b78>] v4l2_release+0x3c/0x84 [ 207.031824] [<ffffffc00033b218>] __fput+0xf8/0x1c0 [ 207.036599] [<ffffffc00033b350>] ____fput+0x1c/0x2c [ 207.041454] [<ffffffc00023ed78>] task_work_run+0xb0/0xd4 [ 207.046756] [<ffffffc00020872c>] do_notify_resume+0x54/0x6c From the log I get in this fail case, the size of unmap here is 0x10080, and its map size of dma_common_pages_remap in __iommu_alloc_attrs is 0x10080, and the corresponding dma-map size is 0x11000(after iova_align). I think all the parameters of map and unmap are good, it look like not a DMA issue. but I don't know why we get this warning. Have you met this problem and give us some advices, Thanks. (If we add PAGE_ALIGN for the size in dma_alloc and dma_free, It is OK.)OK, having dug into this it looks like the root cause comes from some asymmetry in the common code: dma_common_pages remap() just passes the size through to get_vm_area_caller(), and the first thing that does is to page-align it. On the other hand, neither dma_common_free_remap() nor unmap_kernel_range() does anything with the size, so we wind up giving an unaligned end address to vunmap_page_range() and messing up the vmalloc page tables. I wonder if dma_common_free_remap() should be page-aligning the size to match expectations (i.e. make it correctly unmap any request the other functions happily mapped), or conversely, perhaps both the map and unmap functions should have a WARN_ON(size & PAGE_MASK) to enforce being called as actually intended. Laura?
Based on what I've found, the DMA mapping API needs to be able to handle unaligned sizes gracefully so I don't think a warn is appropriate. I was aligning at the higher level but it would be best for dma_common_free_remap to align as well.
Either way, I'll send out a patch to make the arm64 side deal with it explicitly. Robin.
Thanks, Laura _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
