Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration

[Han, Huaitong]

Hi, Gaohuai

I tried to debug the problem, and I found the indirect cause may be that
the rmap value is not cleared when KVM mmu page is freed. I have read
code without the root cause. Can you stable reproduce the the issue?
Many guesses need to be verified.


On Mon, 2017-02-20 at 10:17 +0800, hangaohuai wrote:
> Hi, Kai Huang and Xiao Guangrong.
> 
> For the problem mentioned above, there may be a bug related to PML and 
> probably on Broadwell CPUs.
> 
> I've been reading the code for PML for days, but I haven't found any clews. 
> Do you have any idea about this BUG ?
> 
> Hope you can help!
> 
> On 2017/2/10 23:28, Chris Friesen wrote:
> >
> > Well, not so much solved as worked around it.
> >
> > It seems that the problem only showed up on Broadwell, which made us wonder 
> > about something hardware specific.
> >
> > Setting "kvm-intel.eptad=0" in the kernel boot args seems to mask the 
> > problem for us.
> >
> > Chris
> >
> > On 02/10/2017 03:11 AM, Herongguang (Stephen) wrote:
> >> Hi, Chris Friesen, did you solve the problem?
> >>
> >> On 2017/2/9 22:37, Herongguang (Stephen) wrote:
> >>> Hi.
> >>> I had a problem when I just repeatedly live migrate a vm between two 
> >>> compute
> >>> nodes.
> >>> The phenomenon was that the KVM module was crashed and then the host 
> >>> rebooted.
> >>> However I cannot reliably trigger this BUG.
> >>>
> >>> The backtrace is the same as 
> >>> http://www.spinics.net/lists/kvm/msg138475.html.
> >>>
> >>> The crash is triggered when function __rmap_clear_dirty is invoked and an
> >>> invalid page(0x000000007f183000) is visited.
> >>> The value %rdi is 0x000000007f183000, which is obviously not a valid 
> >>> kernel
> >>> pointer for x86_64.
> >>> The assembly of __rmap_clear_dirty is:
> >>>      0xffffffffa04d9ac0 <__rmap_clear_dirty>:        callq 
> >>> 0xffffffff816543d0
> >>> <ftrace_caller>
> >>>      0xffffffffa04d9ac5 <__rmap_clear_dirty+5>:      push %rbp
> >>>      0xffffffffa04d9ac6 <__rmap_clear_dirty+6>:      mov %rsp,%rbp
> >>>      0xffffffffa04d9ac9 <__rmap_clear_dirty+9>:      push %rbx
> >>>      0xffffffffa04d9aca <__rmap_clear_dirty+10>:     sub $0x18,%rsp
> >>>      0xffffffffa04d9ace <__rmap_clear_dirty+14>:     mov (%rsi),%rdi
> >>>      0xffffffffa04d9ad1 <__rmap_clear_dirty+17>:     mov %gs:0x28,%rax
> >>>      0xffffffffa04d9ada <__rmap_clear_dirty+26>:     mov %rax,-0x10(%rbp)
> >>>      0xffffffffa04d9ade <__rmap_clear_dirty+30>:     xor %eax,%eax
> >>>      0xffffffffa04d9ae0 <__rmap_clear_dirty+32>:     test %rdi,%rdi
> >>>      0xffffffffa04d9ae3 <__rmap_clear_dirty+35>:     je 0xffffffffa04d9b78
> >>>      0xffffffffa04d9ae9 <__rmap_clear_dirty+41>:     test $0x1,%dil
> >>>      0xffffffffa04d9aed <__rmap_clear_dirty+45>:     je 0xffffffffa04d9b98
> >>>      0xffffffffa04d9af3 <__rmap_clear_dirty+51>:     and 
> >>> $0xfffffffffffffffe,%rdi
> >>>      0xffffffffa04d9af7 <__rmap_clear_dirty+55>:     movl $0x0,-0x18(%rbp)
> >>>      0xffffffffa04d9afe <__rmap_clear_dirty+62>:     mov %rdi,-0x20(%rbp)
> >>>      0xffffffffa04d9b02 <__rmap_clear_dirty+66>:     mov (%rdi),%rdi
> >>>      0xffffffffa04d9b05 <__rmap_clear_dirty+69>:     test %rdi,%rdi
> >>>                                     ...
> >>>
> >>> The details of the environment is:
> >>> Host info: x86_64 CentOS 7 kernel (3.10.0-327.36.58.10_2.x86_64, slightly
> >>> modified). The CPU is Broadwell Intel(R) Xeon(R) CPU E5-2618L v4 @ 
> >>> 2.20GHz.
> >>> Kmod info: version is 4.4.36
> >>> What I know is that the parameter PML(Page Modification Logging) is 
> >>> enabled by
> >>> default.
> >>>      # cat /sys/module/kvm_intel/parameters/pml
> >>>      # Y
> >>>
> >>> Below is the crash message:
> >>> [1548777.924180] kvm: zapping shadow pages for mmio generation wraparound
> >>> [1548777.947844] HTB: quantum of class 10001 is big. Consider r2q change.
> >>> [1548778.185389] kvm: zapping shadow pages for mmio generation wraparound
> >>> [1548778.994801] BUG: unable to handle kernel paging request at 
> >>> 000000007f183000
> >>> [1548779.002135] IP: [<ffffffffa04d9b0a>] __rmap_clear_dirty+0x4a/0xf0 
> >>> [kvm]
> >>> [1548779.009151] PGD 1f8452067 PUD 0
> >>> [1548779.012774] Thread overran stack, or stack corrupted
> >>> [1548779.018076] Oops: 0000 [#1] SMP
> >>> [1548779.027050] collected_len = 1048570, LOG_BUF_LEN_LOCAL = 1048576
> >>> [1548779.042039] kbox: no notify die func register. no need to notify
> >>> [1548779.048392] do nothing after die!
> >>> [1548779.052071] Modules linked in: kboxdriver(O) kbox(O) sch_htb
> >>> ip_set_hash_net ip6table_filter ip6_tables iptable_filter igb_uio(OE) uio
> >>> bridge dm_service_time dm_multipath iscsi_tcp libiscsi_tcp libiscsi
> >>> scsi_transport_iscsi 8021q garp stp mrp llc vfat fat isofs ext4 jbd2 xfs
> >>> sha512_generic dev_connlimit(O) bum(O) ip_set nfnetlink prio(O) nat(O)
> >>> vport_vxlan(O) openvswitch(O) nf_defrag_ipv6 gre ib_uverbs(OVE) 
> >>> hotpatch(OE)
> >>> sigma_serial(O) pmcint(O) guest_kbox_ram(O) signo_catch(O) mlx4_ib(OVE)
> >>> mlx4_en(OVE) vxlan ip6_udp_tunnel udp_tunnel ib_sa(OVE) ib_mad(OVE) ptp
> >>> ib_core(OVE) ib_addr(OVE) pps_core ib_netlink(OVE) intel_powerclamp 
> >>> coretemp
> >>> intel_rapl crc32_pclmul crc32c_intel ipmi_devintf(OVE) ghash_clmulni_intel
> >>> mlx4_core(OVE) aesni_intel kvm_intel(O) igb(OVE) lrw gf128mul i2c_algo_bit
> >>> glue_helper
> >>> [1548779.125577]  iTCO_wdt ablk_helper kvm(O) iTCO_vendor_support sg 
> >>> cryptd
> >>> compat(OVE) dca sb_edac i2c_i801 kbox_pci(OVE) i2c_core edac_core pcspkr
> >>> lpc_ich shpchp mfd_core ipmi_si(OVE) ipmi_msghandler(OVE) 
> >>> nf_conntrack_ipv4
> >>> nf_defrag_ipv4 vhost_net(O) tun(O) vhost(O) macvtap macvlan vfio_pci 
> >>> irqbypass
> >>> vfio_iommu_type1 vfio xt_sctp nf_conntrack_proto_sctp nf_nat_proto_sctp 
> >>> nf_nat
> >>> nf_conntrack sctp libcrc32c ip_tables ext3 mbcache jbd sd_mod crc_t10dif
> >>> crct10dif_generic ahci crct10dif_pclmul crct10dif_common libahci 
> >>> mpt2sas(OVE)
> >>> libata raid_class scsi_transport_sas dm_mod [last unloaded: kbox]
> >>> [1548779.178704] CPU: 35 PID: 33769 Comm: migration Tainted: G           
> >>> OE
> >>> ----V-------   3.10.0-327.36.58.10_2.x86_64 #1
> >>> [1548779.189855] Hardware name: HUAWEI TECHNOLOGIES CO.,LTD.
> >>> CH80GPUB8/CH80GPUB8, BIOS GPUBV201 06/18/2015
> >>> [1548779.199585] task: ffff880123da0000 ti: ffff8801a8068000 task.ti:
> >>> ffff8801a8068000
> >>> [1548779.207596] RIP: 0010:[<ffffffffa04d9b0a>] [<ffffffffa04d9b0a>]
> >>> __rmap_clear_dirty+0x4a/0xf0 [kvm]
> >>> [1548779.217209] RSP: 0018:ffff8801a806bba0  EFLAGS: 00010206
> >>> [1548779.222879] RAX: 0000000000000000 RBX: 0000000000000000 RCX:
> >>> 0000000000000000
> >>> [1548779.230543] RDX: ffffc90059d64000 RSI: ffffc90059f2efd0 RDI:
> >>> 000000007f183000
> >>> [1548779.238211] RBP: ffff8801a806bbc0 R08: ffff8801a806bd60 R09:
> >>> 0000000000000100
> >>> [1548779.245878] R10: 0000000000003649 R11: 0000000000000006 R12:
> >>> ffff88027a7f0000
> >>> [1548779.253524] R13: ffffffffa04d9ac0 R14: ffff8801a806bfd8 R15:
> >>> 0000000000000000
> >>> [1548779.261125] FS:  00007f3dd6aff700(0000) GS:ffff883ffe3c0000(0000)
> >>> knlGS:0000000000000000
> >>> [1548779.269733] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> [1548779.275795] CR2: 000000007f183000 CR3: 00000001f50ab000 CR4:
> >>> 00000000003427e0
> >>> [1548779.283444] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> >>> 0000000000000000
> >>> [1548779.291040] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> >>> 0000000000000400
> >>> [1548779.298689] Stack:
> >>> [1548779.301045]  0000000000000000 0000000000000297 0000000009b989ac
> >>> 0000000000000000
> >>> [1548779.309033]  ffff8801a806bc48 ffffffffa04d9206 00ff8801a806bd10
> >>> ffff8801a806bd60
> >>> [1548779.317023]  0000000000000100 00000000000bffff 0000000100000001
> >>> 00000000000396fa
> >>> [1548779.325012] Call Trace:
> >>> [1548779.327856]  [<ffffffffa04d9206>] slot_handle_level_range+0x76/0x100 
> >>> [kvm]
> >>> [1548779.335090]  [<ffffffffa04dac34>] 
> >>> kvm_mmu_slot_leaf_clear_dirty+0x54/0x80
> >>> [kvm]
> >>> [1548779.342922]  [<ffffffffa03f8967>] vmx_slot_enable_log_dirty+0x17/0x30
> >>> [kvm_intel]
> >>> [1548779.350943]  [<ffffffffa04d5d2f>] 
> >>> kvm_arch_commit_memory_region+0x5f/0xe0
> >>> [kvm]
> >>> [1548779.358776]  [<ffffffffa04be7c5>] 
> >>> __kvm_set_memory_region+0x665/0xa90 [kvm]
> >>> [1548779.366099]  [<ffffffffa04be160>] ? kvm_kvzalloc+0x30/0x30 [kvm]
> >>> [1548779.372457]  [<ffffffffa04bec1b>] kvm_set_memory_region+0x2b/0x40 
> >>> [kvm]
> >>> [1548779.379423]  [<ffffffffa04bf084>] kvm_vm_ioctl+0x454/0x700 [kvm]
> >>> [1548779.385777]  [<ffffffff8112f083>] ? ftrace_ops_list_func+0x83/0x110
> >>> [1548779.392406]  [<ffffffffa04bec30>] ? kvm_set_memory_region+0x40/0x40 
> >>> [kvm]
> >>> [1548779.399538]  [<ffffffff811fceb5>] do_vfs_ioctl+0x2e5/0x4c0
> >>> [1548779.405340]  [<ffffffff811fd131>] SyS_ioctl+0xa1/0xc0
> >>> [1548779.410736]  [<ffffffff81652809>] system_call_fastpath+0x16/0x1b
> >>> [1548779.417086] Code: c0 48 85 ff 0f 84 8f 00 00 00 40 f6 c7 01 0f 84 a5 
> >>> 00
> >>> 00 00 48 83 e7 fe c7 45 e8 00 00 00 00 48 89 7d e0 48 8b 3f 48 85 ff 74 6e
> >>> <48> 8b 17 f6 c2 01 74 5d 48 8b 05 c7 40 04 00 48 89 d1 31 db 48
> >>> [1548779.438015] RIP  [<ffffffffa04d9b0a>] __rmap_clear_dirty+0x4a/0xf0 
> >>> [kvm]
> >>> [1548779.445109]  RSP <ffff8801a806bba0>
> >>> [1548779.448915] CR2: 000000007f183000
> >>> [1548779.453070] ---[ end trace d99f28b71290c64c ]---
> >>> [1548779.523937] Kernel panic - not syncing: Fatal exception
> >>> [1548779.523945] perf interrupt took too long (124114 > 17857), lowering
> >>> kernel.perf_event_max_sample_rate to 7000
> >>> [1548779.524826] perf interrupt took too long (123163 > 31250), lowering
> >>> kernel.perf_event_max_sample_rate to 4000
> >>> [1548779.525717] perf interrupt took too long (122216 > 62500), lowering
> >>> kernel.perf_event_max_sample_rate to 2000
> >>> [1548779.603824] die even has been record!
> >>
> >
> >
> >
> > .
> >
>