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?
Either way, I'll send out a patch to make the arm64 side deal with it
explicitly.
Robin.
>
>> + } else {
>> + iommu_dma_unmap_page(dev, handle, size, 0, NULL);
>> + __free_pages(virt_to_page(cpu_addr), get_order(size));
>> + }
>> +}
>> +
> [...]
>
>