On 11.08.2016 05:10, Bob Liu wrote: > > On 08/10/2016 10:54 PM, Evgenii Shatokhin wrote: >> On 10.08.2016 15:49, Bob Liu wrote: >>> >>> On 08/10/2016 08:33 PM, Evgenii Shatokhin wrote: >>>> On 14.07.2016 15:04, Bob Liu wrote: >>>>> >>>>> On 07/14/2016 07:49 PM, Evgenii Shatokhin wrote: >>>>>> On 11.07.2016 15:04, Bob Liu wrote: >>>>>>> >>>>>>> >>>>>>> On 07/11/2016 04:50 PM, Evgenii Shatokhin wrote: >>>>>>>> On 06.06.2016 11:42, Dario Faggioli wrote: >>>>>>>>> Just Cc-ing some Linux, block, and Xen on CentOS people... >>>>>>>>> >>>>>>>> >>>>>>>> Ping. >>>>>>>> >>>>>>>> Any suggestions how to debug this or what might cause the problem? >>>>>>>> >>>>>>>> Obviously, we cannot control Xen on the Amazon's servers. But perhaps there is something we can do at the kernel's side, is it? >>>>>>>> >>>>>>>>> On Mon, 2016-06-06 at 11:24 +0300, Evgenii Shatokhin wrote: >>>>>>>>>> (Resending this bug report because the message I sent last week did >>>>>>>>>> not >>>>>>>>>> make it to the mailing list somehow.) >>>>>>>>>> >>>>>>>>>> Hi, >>>>>>>>>> >>>>>>>>>> One of our users gets kernel panics from time to time when he tries >>>>>>>>>> to >>>>>>>>>> use his Amazon EC2 instance with CentOS7 x64 in it [1]. Kernel panic >>>>>>>>>> happens within minutes from the moment the instance starts. The >>>>>>>>>> problem >>>>>>>>>> does not show up every time, however. >>>>>>>>>> >>>>>>>>>> The user first observed the problem with a custom kernel, but it was >>>>>>>>>> found later that the stock kernel 3.10.0-327.18.2.el7.x86_64 from >>>>>>>>>> CentOS7 was affected as well. >>>>>>> >>>>>>> Please try this patch: >>>>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7b0767502b5db11cb1f0daef2d01f6d71b1192dc >>>>>>> >>>>>>> Regards, >>>>>>> Bob >>>>>>> >>>>>> >>>>>> Unfortunately, it did not help. The same BUG_ON() in blkfront_setup_indirect() still triggers in our kernel based on RHEL's 3.10.0-327.18.2, where I added the patch. >>>>>> >>>>>> As far as I can see, the patch makes sure the indirect pages are added to the list only if (!info->feature_persistent) holds. I suppose it holds in our case and the pages are added to the list because the triggered BUG_ON() is here: >>>>>> >>>>>> if (!info->feature_persistent && info->max_indirect_segments) { >>>>>> <...> >>>>>> BUG_ON(!list_empty(&info->indirect_pages)); >>>>>> <...> >>>>>> } >>>>>> >>>>> >>>>> That's odd. >>>>> Could you please try to reproduce this issue with a recent upstream kernel? >>>>> >>>>> Thanks, >>>>> Bob >>>> >>>> No luck with the upstream kernel 4.7.0 so far due to unrelated issues (bad initrd, I suppose, so the system does not even boot). >>>> >>>> However, the problem reproduced with the stable upstream kernel 3.14.74. After the system booted the second time with this kernel, that BUG_ON triggered: >>>> kernel BUG at drivers/block/xen-blkfront.c:1701 >>>> >>> >>> Could you please provide more detail on how to reproduce this bug? I'd like to have a test. >>> >>> Thanks! >>> Bob >> >> As the user says, he uses an Amazon EC2 instance. Namely: HVM CentOS7 AMI on a c3.large instance with EBS magnetic storage. >> > > Oh, then it would be difficult to debug this issue. > The xen-blkfront communicates with xen-blkback(in dom0 or driver domain), but that part is a black box when running Amazon EC2. > We can't see the source code of the backend side! Yes, and another problem is, I am still unable to reproduce the issue in my EC2 instance. However, the problem shows up rather often in the user's instance. > > Can this bug be reproduced on your own environment(xen + dom0)? I haven't tried this yet. > >> At least 2 LVM partitions are needed: >> * /, 20-30 Gb should be enough, ext4 >> * /vz, 5-10 Gb should be enough, ext4 >> >> Kernel 3.14.74 I was talking about: https://www.dropbox.com/s/bhus3mubza87z86/kernel-3.14.74-1.test.x86_64.rpm?dl=1 >> >> Not sure if it is relevant, but the user may have installed additional packages from https://download.openvz.org/virtuozzo/releases/7.0-rtm/x86_64/os/ repository. Namely: vzctl, vzmigrate, vzprocps, vztt-lib, vzctcalc, ploop, prlctl, centos-7-x86_64-ez. >> >> After the kernel and the other mentioned packages have been installed, >> the user rebooted the instance to run that kernel 3.14.74. >> >> Then - start the instance, wait 5 minutes, stop the instance, repeat. 2-20 such iterations were usually enough to reproduce the problem. Can be automated with the help of Amazon's API. >> >> BTW, before the BUG_ON triggered this time, there was the following in dmesg. Not sure if it is related but still: >> > > Attach the full dmesg would be better. Well, there is not much in the part the user was able to retrieve besides what I have sent and the BUG_ON() splat. But here it is, anyway. Regards, Evgenii > > Regards, > Bob > >> ---------------------- >> [ 2.835034] scsi0 : ata_piix >> [ 2.840317] scsi1 : ata_piix >> [ 2.842267] ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xc100 irq 14 >> [ 2.845861] ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xc108 irq 15 >> [ 2.853840] AVX version of gcm_enc/dec engaged. >> [ 2.859963] xen_netfront: Initialising Xen virtual ethernet driver >> [ 2.867156] alg: No test for __gcm-aes-aesni (__driver-gcm-aes-aesni) >> [ 2.885861] blkfront: xvda: barrier or flush: disabled; persistent grants: disabled; indirect descriptors: enabled; >> [ 2.889046] alg: No test for crc32 (crc32-pclmul) >> [ 2.899290] xvda: xvda1 >> [ 2.997751] blkfront: xvdc: flush diskcache: enabled; persistent grants: disabled; indirect descriptors: enabled; >> [ 3.007401] xvdc: unknown partition table >> [ 3.010465] Setting capacity to 31992832 >> [ 3.012922] xvdc: detected capacity change from 0 to 16380329984 >> [ 3.017408] blkfront: xvdd: flush diskcache: enabled; persistent grants: disabled; indirect descriptors: enabled; >> [ 3.023861] xvdd: unknown partition table >> [ 3.026481] Setting capacity to 31992832 >> [ 3.029051] xvdd: detected capacity change from 0 to 16380329984 >> [ 3.033320] blkfront: xvdf: barrier or flush: disabled; persistent grants: disabled; indirect descriptors: enabled; >> [ 3.040712] random: nonblocking pool is initialized >> [ 3.057432] xvdf: unknown partition table >> [ 3.060807] Setting capacity to 41943040 >> [ 3.063194] xvdf: detected capacity change from 0 to 21474836480 >> [ 3.067684] blkfront: xvdb: barrier or flush: disabled; persistent grants: disabled; indirect descriptors: enabled; >> [ 3.076835] xvdb: unknown partition table >> [ 3.079692] Setting capacity to 16777216 >> [ 3.082112] xvdb: detected capacity change from 0 to 8589934592 >> [ 3.086853] vbd vbd-51712: 16 xlvbd_add at /local/domain/0/backend/vbd/9543/51712 >> ---------------------- >> >>> >>>>> >>>>>> So the problem is still out there somewhere, it seems. >>>>>> >>>>>> Regards, >>>>>> Evgenii >>>>>> >>>>>>>>>> >>>>>>>>>> The part of the system log he was able to retrieve is attached. Here >>>>>>>>>> is >>>>>>>>>> the bug info, for convenience: >>>>>>>>>> >>>>>>>>>> ------------------------------------ >>>>>>>>>> [ 2.246912] kernel BUG at drivers/block/xen-blkfront.c:1711! >>>>>>>>>> [ 2.246912] invalid opcode: 0000 [#1] SMP >>>>>>>>>> [ 2.246912] Modules linked in: ata_generic pata_acpi >>>>>>>>>> crct10dif_pclmul >>>>>>>>>> crct10dif_common crc32_pclmul crc32c_intel ghash_clmulni_intel >>>>>>>>>> xen_netfront xen_blkfront(+) aesni_intel lrw ata_piix gf128mul >>>>>>>>>> glue_helper ablk_helper cryptd libata serio_raw floppy sunrpc >>>>>>>>>> dm_mirror >>>>>>>>>> dm_region_hash dm_log dm_mod scsi_transport_iscsi >>>>>>>>>> [ 2.246912] CPU: 1 PID: 50 Comm: xenwatch Not tainted >>>>>>>>>> 3.10.0-327.18.2.el7.x86_64 #1 >>>>>>>>>> [ 2.246912] Hardware name: Xen HVM domU, BIOS 4.2.amazon >>>>>>>>>> 12/07/2015 >>>>>>>>>> [ 2.246912] task: ffff8800e9fcb980 ti: ffff8800e98bc000 task.ti: >>>>>>>>>> ffff8800e98bc000 >>>>>>>>>> [ 2.246912] RIP: 0010:[] [] >>>>>>>>>> blkfront_setup_indirect+0x41f/0x430 [xen_blkfront] >>>>>>>>>> [ 2.246912] RSP: 0018:ffff8800e98bfcd0 EFLAGS: 00010283 >>>>>>>>>> [ 2.246912] RAX: ffff8800353e15c0 RBX: ffff8800e98c52c8 RCX: >>>>>>>>>> 0000000000000020 >>>>>>>>>> [ 2.246912] RDX: ffff8800353e15b0 RSI: ffff8800e98c52b8 RDI: >>>>>>>>>> ffff8800353e15d0 >>>>>>>>>> [ 2.246912] RBP: ffff8800e98bfd20 R08: ffff8800353e15b0 R09: >>>>>>>>>> ffff8800eb403c00 >>>>>>>>>> [ 2.246912] R10: ffffffffa0155532 R11: ffffffffffffffe8 R12: >>>>>>>>>> ffff8800e98c4000 >>>>>>>>>> [ 2.246912] R13: ffff8800e98c52b8 R14: 0000000000000020 R15: >>>>>>>>>> ffff8800353e15c0 >>>>>>>>>> [ 2.246912] FS: 0000000000000000(0000) GS:ffff8800efc20000(0000) >>>>>>>>>> knlGS:0000000000000000 >>>>>>>>>> [ 2.246912] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>>>>>>>> [ 2.246912] CR2: 00007f1b615ef000 CR3: 00000000e2b44000 CR4: >>>>>>>>>> 00000000001406e0 >>>>>>>>>> [ 2.246912] DR0: 0000000000000000 DR1: 0000000000000000 DR2: >>>>>>>>>> 0000000000000000 >>>>>>>>>> [ 2.246912] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: >>>>>>>>>> 0000000000000400 >>>>>>>>>> [ 2.246912] Stack: >>>>>>>>>> [ 2.246912] 0000000000000020 0000000000000001 00000020a0157217 >>>>>>>>>> 00000100e98bfdbc >>>>>>>>>> [ 2.246912] 0000000027efa3ef ffff8800e98bfdbc ffff8800e98ce000 >>>>>>>>>> ffff8800e98c4000 >>>>>>>>>> [ 2.246912] ffff8800e98ce040 0000000000000001 ffff8800e98bfe08 >>>>>>>>>> ffffffffa0155d4c >>>>>>>>>> [ 2.246912] Call Trace: >>>>>>>>>> [ 2.246912] [] blkback_changed+0x4ec/0xfc8 >>>>>>>>>> [xen_blkfront] >>>>>>>>>> [ 2.246912] [] ? xenbus_gather+0x170/0x190 >>>>>>>>>> [ 2.246912] [] ? __slab_free+0x10e/0x277 >>>>>>>>>> [ 2.246912] [] >>>>>>>>>> xenbus_otherend_changed+0xad/0x110 >>>>>>>>>> [ 2.246912] [] ? xenwatch_thread+0x77/0x180 >>>>>>>>>> [ 2.246912] [] backend_changed+0x13/0x20 >>>>>>>>>> [ 2.246912] [] xenwatch_thread+0x66/0x180 >>>>>>>>>> [ 2.246912] [] ? wake_up_atomic_t+0x30/0x30 >>>>>>>>>> [ 2.246912] [] ? >>>>>>>>>> unregister_xenbus_watch+0x1f0/0x1f0 >>>>>>>>>> [ 2.246912] [] kthread+0xcf/0xe0 >>>>>>>>>> [ 2.246912] [] ? >>>>>>>>>> kthread_create_on_node+0x140/0x140 >>>>>>>>>> [ 2.246912] [] ret_from_fork+0x58/0x90 >>>>>>>>>> [ 2.246912] [] ? >>>>>>>>>> kthread_create_on_node+0x140/0x140 >>>>>>>>>> [ 2.246912] Code: e1 48 85 c0 75 ce 49 8d 84 24 40 01 00 00 48 89 >>>>>>>>>> 45 >>>>>>>>>> b8 e9 91 fd ff ff 4c 89 ff e8 8d ae 06 e1 e9 f2 fc ff ff 31 c0 e9 2e >>>>>>>>>> fe >>>>>>>>>> ff ff <0f> 0b e8 9a 57 f2 e0 0f 0b 0f 1f 84 00 00 00 00 00 0f 1f 44 >>>>>>>>>> 00 >>>>>>>>>> [ 2.246912] RIP [] >>>>>>>>>> blkfront_setup_indirect+0x41f/0x430 [xen_blkfront] >>>>>>>>>> [ 2.246912] RSP >>>>>>>>>> [ 2.491574] ---[ end trace 8a9b992812627c71 ]--- >>>>>>>>>> [ 2.495618] Kernel panic - not syncing: Fatal exception >>>>>>>>>> ------------------------------------ > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > https://lists.xen.org/xen-devel >