Propper use of pci_map_sg
Malte Vesper
malte.vesper at postgrad.manchester.ac.uk
Tue Feb 3 13:13:31 EST 2015
The problem was that I did not know to call `sg_init_table`, it is not
sufficient to just init the seperate entries with sg_set_page.
On 02/02/15 19:49, Malte Vesper wrote:
> Since my last mail went unanswered I did some further investigation. I
> compiled a kernel with the DMA-API debug fs support and got the dmesg
> output below. Note how I run the program 3 times and it only reports
> on the third run that the page mapping count is off. The thing
> confusing me the most about this, is that I can't see where I go
> wrong. Since I call pci_map_sg and pci_unmap_sg directly after each
> other there is no room for parameter modification. (I have only one
> device, and the interrupt handler has output when invoked). So what is
> wrong with:
>
> mapped =*pci_map_sg*(pcidev, scatterlist, pinned,
> DMA_BIDIRECTIONAL);
> *pci_unmap_sg*(pcidev, scatterlist, pinned, DMA_BIDIRECTIONAL);
>
> Do I have to recreate the vanilla scatterlist for pci_unmap_sg?
>
> Any hints/help is highly appreciated.
>
> Ted
>
>
>
> Dmesg output:
>
> [ 2087.171247] SCAS FPGA 0000:01:00.0: [fpga+]: Removing device 0
> [ 2087.171771] [fpga+]: SCAS MAJOR UNREGISTERED: 100
> [ 2087.180070] [fpga+]: fpga+ registered with major number 100
> [ 2087.180096] SCAS FPGA 0000:01:00.0: Probing
> [ 2087.180163] SCAS FPGA 0000:01:00.0: irq 66 for MSI/MSI-X
> [ 2087.180182] SCAS FPGA 0000:01:00.0: [fpga+]: Board tied to slot 0
> [ 2092.359203] [fpga+]: IOCTL 2148040970
> [ 2092.359206] [fpga+]: MINOR: 0
> [ 2092.359207] [fpga+]: ARG: 140736686734672
> [ 2092.359210] SCAS FPGA 0000:01:00.0: [fpga+]: IOCTL:
> IOCTL_FPGA_PIN_PAGE
> [ 2092.359211] Testers hell
> [ 2092.359215] pinned 2
> [ 2092.359216] setting page: 0
> [ 2092.359217] setting page: 1
> [ 2092.359223] Mapped: 2
> [ 2092.359227] Done
> [ 2117.846740] [fpga+]: IOCTL 2148040970
> [ 2117.846742] [fpga+]: MINOR: 0
> [ 2117.846743] [fpga+]: ARG: 140735106116944
> [ 2117.846746] SCAS FPGA 0000:01:00.0: [fpga+]: IOCTL:
> IOCTL_FPGA_PIN_PAGE
> [ 2117.846746] Testers hell
> [ 2117.846749] pinned 2
> [ 2117.846749] setting page: 0
> [ 2117.846750] setting page: 1
> [ 2117.846755] Mapped: 2
> [ 2117.846759] Done
> [ 2124.136132] [fpga+]: IOCTL 2148040970
> [ 2124.136134] [fpga+]: MINOR: 0
> [ 2124.136135] [fpga+]: ARG: 140735560133008
> [ 2124.136138] SCAS FPGA 0000:01:00.0: [fpga+]: IOCTL:
> IOCTL_FPGA_PIN_PAGE
> [ 2124.136138] Testers hell
> [ 2124.136141] pinned 2
> [ 2124.136142] setting page: 0
> [ 2124.136142] setting page: 1
> [ 2124.136147] Mapped: 2
> [ 2124.136152] Done
> [ 2124.136251] BUG: Bad page map in process dma
> pte:8000000f7b983867 pmd:fa9d31067
> [ 2124.136254] page:ffffea003dee60c0 count:1 mapcount:-30705
> mapping:ffff880fadddb901 index:0xc0054000afddc901
> [ 2124.136254] flags:
> 0x2ffff000008006c(referenced|uptodate|lru|active|swapbacked)
> [ 2124.136257] page dumped because: bad pte
> [ 2124.136258] addr:0000000001382000 vm_flags:08100073
> anon_vma:ffff880fadddb900 mapping: (null) index:1382
> [ 2124.136261] CPU: 6 PID: 6902 Comm: dma Tainted: G B W OE
> 3.18.5hotdog #2
> [ 2124.136261] Hardware name: System manufacturer System Product
> Name/RAMPAGE IV BLACK EDITION, BIOS 0701 06/04/2014
> [ 2124.136262] ffff880fb842eac8 ffff880fd4093c58 ffffffff8176ab0c
> 0000000000000000
> [ 2124.136264] 0000000001382000 ffff880fd4093ca8 ffffffff8119215a
> 8000000f7b983867
> [ 2124.136265] 0000000000001382 ffff880fd4093ca8 ffff880fa9d31c10
> ffffea003dee60c0
> [ 2124.136267] Call Trace:
> [ 2124.136270] [<ffffffff8176ab0c>] dump_stack+0x46/0x58
> [ 2124.136274] [<ffffffff8119215a>] print_bad_pte+0x1aa/0x250
> [ 2124.136275] [<ffffffff8119367f>] unmap_single_vma+0x76f/0x8f0
> [ 2124.136278] [<ffffffff81175cf0>] ? put_pages_list+0x70/0x70
> [ 2124.136279] [<ffffffff811942d1>] unmap_vmas+0x51/0xa0
> [ 2124.136281] [<ffffffff8119d48c>] exit_mmap+0x9c/0x170
> [ 2124.136284] [<ffffffff8106c1c4>] mmput+0x64/0x130
> [ 2124.136286] [<ffffffff810716ec>] do_exit+0x27c/0xa80
> [ 2124.136287] [<ffffffff81071f7f>] do_group_exit+0x3f/0xa0
> [ 2124.136290] [<ffffffff81071ff4>] SyS_exit_group+0x14/0x20
> [ 2124.136292] [<ffffffff81772f6d>] system_call_fastpath+0x16/0x1b
> [ 2124.136319] BUG: Bad page state in process dma pfn:f7b983
> [ 2124.136320] page:ffffea003dee60c0 count:0 mapcount:-30705
> mapping: (null) index:0xc0054000afddc901
> [ 2124.136321] flags:
> 0x2ffff000008000c(referenced|uptodate|swapbacked)
> [ 2124.136322] page dumped because: nonzero mapcount
> [ 2124.136323] Modules linked in: fpga+(OE) hid_generic nfsv3
> rpcsec_gss_krb5 nfsv4 vmw_vsock_vmci_transport vsock vmw_vmci
> autofs4 nfsd auth_rpcgss nfs_acl nfs snd_hda_codec_realtek
> snd_hda_codec_generic snd_hda_codec_hdmi snd_hda_intel
> snd_hda_controller snd_hda_codec x86_pkg_temp_thermal
> intel_powerclamp snd_hwdep coretemp rfcomm snd_pcm kvm_intel kvm
> bnep lockd bluetooth snd_seq_midi snd_seq_midi_event snd_rawmidi
> snd_seq grace sunrpc eeepc_wmi asus_wmi snd_seq_device snd_timer
> sparse_keymap joydev video mei_me sb_edac snd edac_core mei
> serio_raw lpc_ich soundcore fscache binfmt_misc nls_iso8859_1
> parport_pc ppdev mac_hid tpm_infineon cp210x usbserial lp parport
> dm_crypt hid_microsoft usbhid hid radeon i2c_algo_bit ttm
> drm_kms_helper mxm_wmi drm crct10dif_pclmul crc32_pclmul e1000e
> ghash_clmulni_intel aesni_intel psmouse aes_x86_64 lrw gf128mul
> glue_helper ablk_helper cryptd aacraid ahci ptp libahci pps_core
> wmi [last unloaded: fpga+]
> [ 2124.136351] CPU: 6 PID: 6902 Comm: dma Tainted: G B W OE
> 3.18.5hotdog #2
> [ 2124.136352] Hardware name: System manufacturer System Product
> Name/RAMPAGE IV BLACK EDITION, BIOS 0701 06/04/2014
> [ 2124.136353] ffffffff81aa55c7 ffff880fd4093bb8 ffffffff8176ab0c
> 0000000000000000
> [ 2124.136354] ffffea003dee60c0 ffff880fd4093be8 ffffffff81767527
> ff0000ffffffffff
> [ 2124.136355] ffffea003dee60c0 0000000000000000 00ffff0000000000
> ffff880fd4093c38
> [ 2124.136356] Call Trace:
> [ 2124.136358] [<ffffffff8176ab0c>] dump_stack+0x46/0x58
> [ 2124.136360] [<ffffffff81767527>] bad_page.part.50+0xe0/0xfe
> [ 2124.136362] [<ffffffff8116c91d>] free_pages_prepare+0x16d/0x190
> [ 2124.136363] [<ffffffff8116f1a5>] free_hot_cold_page+0x35/0x180
> [ 2124.136365] [<ffffffff8116f33e>] free_hot_cold_page_list+0x4e/0xa0
> [ 2124.136366] [<ffffffff81176076>] release_pages+0x1f6/0x270
> [ 2124.136368] [<ffffffff811a88bd>]
> free_pages_and_swap_cache+0x8d/0xa0
> [ 2124.136370] [<ffffffff81191b04>] tlb_flush_mmu_free+0x34/0x60
> [ 2124.136371] [<ffffffff81192524>] tlb_flush_mmu+0x24/0x30
> [ 2124.136373] [<ffffffff81192544>] tlb_finish_mmu+0x14/0x40
> [ 2124.136374] [<ffffffff8119d4bb>] exit_mmap+0xcb/0x170
> [ 2124.136376] [<ffffffff8106c1c4>] mmput+0x64/0x130
> [ 2124.136378] [<ffffffff810716ec>] do_exit+0x27c/0xa80
> [ 2124.136379] [<ffffffff81071f7f>] do_group_exit+0x3f/0xa0
> [ 2124.136381] [<ffffffff81071ff4>] SyS_exit_group+0x14/0x20
> [ 2124.136382] [<ffffffff81772f6d>] system_call_fastpath+0x16/0x1b
> ted at ted-headlessBrute:~$
>
>
>
>
>
> On 29/01/15 19:50, Malte Vesper wrote:
>> Hi,
>> I am trying to use pci_map_sg in combination with get_user_pages_fast
>> for a driver. However my code screws the processes memory map over.
>> For easier testing I bundled the piinin/unpinning and mapping
>> unmapping into one ioctl call. The following code misses all the
>> checks on return values, since it is only inteneded as a MWE.
>>
>> When I run my code I get a "*BUG: Bad page map in process ...*",
>> after "Done" is printed.
>>
>> I tried following DMA-API-howto.txt and looking at other code, but I
>> fail to see where I go wrong.
>>
>> Regards, Ted
>>
>>
>> Code from the IOCTL handler:
>>
>> case IOCTL_FPGA_PIN_PAGE:
>> {
>> struct pageInfo pageInfo;
>>
>> dev_dbg(&pcidev->dev, pr_fmt("IOCTL:
>> IOCTL_FPGA_PIN_PAGE\n"));
>>
>> if(!copy_from_user(&pageInfo, (void*)arg, sizeof(struct
>> pageInfo))) {
>> //horrible test
>> const int noPages = pageInfo.size/PAGE_SIZE;
>> int pinned;
>> int mapped = 0;
>> struct scatterlist* scatterlist;
>> printk("Test start\n");
>> //userspacestartpointer, nopages, write?, page* array
>> struct page** pages=kmalloc(sizeof(struct
>> page*)*noPages, GFP_KERNEL);
>> pinned=*get_user_pages_fast*((unsigned
>> long)pageInfo.start, noPages, 1, pages);
>>
>> scatterlist = kmalloc(sizeof(struct
>> scatterlist)*pinned, GFP_KERNEL);
>>
>> for(int i=0; i<pinned; ++i) {
>> sg_set_page(&scatterlist[i], pages[i], PAGE_SIZE, 0);
>> }
>>
>> mapped =*pci_map_sg*(pcidev, scatterlist, pinned,
>> DMA_BIDIRECTIONAL);
>> *pci_unmap_sg*(pcidev, scatterlist, pinned, DMA_BIDIRECTIONAL);
>>
>> for(int i=0; i<pinned; ++i) {
>> *put_page*(pages[i]); //I did place a print here and got two pages
>> unpinned as I expected
>> }
>> kfree(scatterlist);
>> kfree(pages);
>> printk("Done\n");
>> /*pageInfo.pageId = getPageId(getArea(&pageInfo));
>> copy_to_user((void*)arg, &pageInfo, sizeof(struct
>> pageInfo));*/
>> return pageInfo.pageId;
>> } else {
>> return -EFAULT;
>> }
>> }
>> break;
>>
>> P.S.: I used the following code to allocate the memory in userspace,
>> and I use chunk and chunksize to fill pageInfo.start and
>> pageInfo.size respectivly:
>>
>> const int pagesize = sysconf(_SC_PAGESIZE);
>> const int chunksize = 2*pagesize;
>> void* chunk;
>>
>> if(int error = posix_memalign(&chunk, pagesize, chunksize)) {
>> std::cout << "Could not get a page." << std::endl;
>> return error;
>> }
>>
>>
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>> Kernelnewbies at kernelnewbies.org
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>
>
>
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