From mboxrd@z Thu Jan 1 00:00:00 1970 From: labbott@redhat.com (Laura Abbott) Date: Wed, 4 Nov 2015 09:35:26 -0800 Subject: [PATCH v6 2/3] arm64: Add IOMMU dma_ops In-Reply-To: <563A0419.9070100@arm.com> References: <80cb035144a2648a5d94eb1fec3336f17ad249f1.1443718557.git.robin.murphy@arm.com> <1446626388.6400.21.camel@mhfsdcap03> <563A0419.9070100@arm.com> Message-ID: <563A41DE.2010902@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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] [] dump_backtrace+0x0/0x140 >> [ 206.931905] [] show_stack+0x1c/0x28 >> [ 206.939158] [] dump_stack+0x74/0x94 >> [ 206.947459] [] warn_slowpath_common+0x90/0xb8 >> [ 206.954100] [] warn_slowpath_null+0x34/0x44 >> [ 206.961537] [] vunmap_page_range+0x18c/0x1b4 >> [ 206.967630] [] unmap_kernel_range+0x2c/0x78 >> [ 206.976977] [] dma_common_free_remap+0x68/0x80 >> [ 206.983581] [] __iommu_free_attrs+0x14c/0x160 >> [ 206.989646] [] mtk_vcodec_mem_free+0xa0/0x15c >> [ 206.996481] [] vp9_free_work_buf+0x54/0x70 >> [ 207.002260] [] vdec_vp9_deinit+0x7c/0xe8 >> [ 207.008134] [] vdec_if_deinit+0x84/0xec >> [ 207.013820] [] mtk_vcodec_vdec_release+0x54/0x6c >> [ 207.020672] [] fops_vcodec_release+0x7c/0xf8 >> [ 207.026607] [] v4l2_release+0x3c/0x84 >> [ 207.031824] [] __fput+0xf8/0x1c0 >> [ 207.036599] [] ____fput+0x1c/0x2c >> [ 207.041454] [] task_work_run+0xb0/0xd4 >> [ 207.046756] [] 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