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@@ -1,371 +0,0 @@
-
-guest migration 100% cpu freeze bug
-
-# Investigate migration cpu hog(100%) bug
-
-I have some issues when migrating from qemu 2.6.2 to qemu 2.11.1.
-The hypervisors are running kernel 4.9.92 on debian stretch with libvirt v4.0.0.
-Linux, libvirt and qemu are all custom compiled.
-
-I migrated around 21.000 vms from qemu 2.6.2 to qemu 2.11.1 and every once in a while a vm is stuck at 100% cpu after the migration from 2.6.2 to 2.11.1. This happend with about 50-60 vms so far.
-
-I attached gdb to a vcpu thread of one stuck vm, and a bt showed the following info:
-#0  0x00007f4f19949dd7 in ioctl () at ../sysdeps/unix/syscall-template.S:84
-#1  0x0000557c9edede47 in kvm_vcpu_ioctl (cpu=cpu@entry=0x557ca1058840, type=type@entry=0xae80) at /home/dbosschieter/src/qemu-pkg/src/accel/kvm/kvm-all.c:2050
-#2  0x0000557c9ededfb6 in kvm_cpu_exec (cpu=cpu@entry=0x557ca1058840) at /home/dbosschieter/src/qemu-pkg/src/accel/kvm/kvm-all.c:1887
-#3  0x0000557c9edcab44 in qemu_kvm_cpu_thread_fn (arg=0x557ca1058840) at /home/dbosschieter/src/qemu-pkg/src/cpus.c:1128
-#4  0x00007f4f19c0f494 in start_thread (arg=0x7f4f053f3700) at pthread_create.c:333
-#5  0x00007f4f19951acf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97
-
-The ioctl call is a ioctl(18, KVM_RUN and it looks like it is looping inside the vm itself.
-
-I saved the state of the VM (with `virsh save`) after I found it was hanging on its vcpu threads. Then I restored this vm on a test environment running the same kernel, QEMU and libvirt version). After the restore the VM still was haning at 100% cpu usage on all the vcpus.
-I tried to use the perf kvm guest option to trace the guest vm with a copy of the kernel, modules and kallsyms files from inside the guest vm and I got the following trace:
-
-$ perf kvm --guest --guestkallsyms=kallsyms --guestmodules=modules record -g -p 14471 -o perf.data
-$ perf kvm --guest --guestkallsyms=kallsyms --guestmodules=modules report -i perf.data --stdio > analyze
-
-# To display the perf.data header info, please use --header/--header-only options.
-#
-#
-# Total Lost Samples: 0
-#
-# Samples: 105K of event 'cycles'
-# Event count (approx.): 67588147605
-#
-# Children      Self  Command  Shared Object            Symbol                                      Parent symbol
-# ........  ........  .......  .......................  ..........................................  .............
-#
-    28.79%    28.79%  :16028   [guest.kernel.kallsyms]  [g] fuse_get_root_inode                     [other]
-    23.48%    23.48%  :16030   [guest.kernel.kallsyms]  [g] ftrace_raw_output_hrtimer_init          [other]
-     7.32%     7.32%  :16029   [guest.kernel.kallsyms]  [g] do_sysfs_unregistration                 [other]
-     4.82%     4.82%  :16029   [guest.kernel.kallsyms]  [g] posix_cpu_clock_get                     [other]
-     4.20%     4.20%  :16030   [guest.kernel.kallsyms]  [g] ftrace_raw_output_timer_expire_entry    [other]
-     3.87%     3.87%  :16029   [guest.kernel.kallsyms]  [g] kvm_init_debugfs                        [other]
-     3.66%     3.66%  :16029   [guest.kernel.kallsyms]  [g] fat_msg                                 [other]
-     3.11%     3.11%  :16029   [guest.kernel.kallsyms]  [g] match_token                             [other]
-     3.07%     3.07%  :16029   [guest.kernel.kallsyms]  [g] load_balance                            [other]
-     1.87%     1.87%  :16029   [guest.kernel.kallsyms]  [g] kvm_pv_guest_cpu_reboot                 [other]
-     1.69%     1.69%  :16031   [guest.kernel.kallsyms]  [g] kvm_init_debugfs                        [other]
-     1.59%     1.59%  :16029   [guest.kernel.kallsyms]  [g] sys_kcmp                                [other]
-     1.19%     1.19%  :16031   [guest.kernel.kallsyms]  [g] save_paranoid                           [other]
-     0.82%     0.82%  :16031   [guest.kernel.kallsyms]  [g] kvm_pv_guest_cpu_reboot                 [other]
-     0.69%     0.69%  :16031   [guest.kernel.kallsyms]  [g] kvm_cpu_notify                          [other]
-     0.54%     0.54%  :16031   [guest.kernel.kallsyms]  [g] rcu_process_callbacks                   [other]
-     0.46%     0.46%  :16030   [guest.kernel.kallsyms]  [g] ftrace_raw_output_hrtimer_start         [other]
-     0.43%     0.43%  :16031   [guest.kernel.kallsyms]  [g] tg_set_cfs_bandwidth                    [other]
-     0.42%     0.42%  :16030   [guest.kernel.kallsyms]  [g] ftrace_raw_output_hrtimer_expire_entry  [other]
-     0.37%     0.37%  :16029   [guest.kernel.kallsyms]  [g] amd_get_mmconfig_range                  [other]
-     0.35%     0.35%  :16031   [guest.kernel.kallsyms]  [g] sys_kcmp                                [other]
-     0.35%     0.35%  :16031   [guest.kernel.kallsyms]  [g] console_unlock                          [other]
-     0.34%     0.34%  :16029   [guest.kernel.kallsyms]  [g] __fat_fs_error                          [other]
-     0.31%     0.31%  :16031   [guest.kernel.kallsyms]  [g] do_sysfs_unregistration                 [other]
-     0.24%     0.24%  :16031   [guest.kernel.kallsyms]  [g] paravirt_write_msr                      [other]
-     0.24%     0.24%  :16029   [guest.kernel.kallsyms]  [g] parse_no_kvmclock                       [other]
-     0.24%     0.24%  :16029   [guest.kernel.kallsyms]  [g] kvm_save_sched_clock_state              [other]
-     0.21%     0.21%  :16030   [guest.kernel.kallsyms]  [g] ptrace_request                          [other]
-     0.20%     0.20%  :16031   [guest.kernel.kallsyms]  [g] print_stack_trace                       [other]
-     0.20%     0.20%  :16031   [guest.kernel.kallsyms]  [g] build_sched_domains                     [other]
-     0.20%     0.20%  :16031   [guest.kernel.kallsyms]  [g] __synchronize_srcu                      [other]
-     0.17%     0.17%  :16031   [guest.kernel.kallsyms]  [g] do_cpu_nanosleep                        [other]
-     0.16%     0.16%  :16031   [guest.kernel.kallsyms]  [g] amd_get_mmconfig_range                  [other]
-     0.16%     0.16%  :16031   [guest.kernel.kallsyms]  [g] irq_node_proc_show                      [other]
-     0.15%     0.15%  :16031   [guest.kernel.kallsyms]  [g] __srcu_read_lock                        [other]
-     0.15%     0.15%  :16031   [guest.kernel.kallsyms]  [g] posix_cpu_nsleep_restart                [other]
-     0.11%     0.11%  :16031   [guest.kernel.kallsyms]  [g] parse_no_kvmclock                       [other]
-     0.11%     0.11%  :16031   [guest.kernel.kallsyms]  [g] __irq_domain_add                        [other]
-     0.11%     0.11%  :16031   [guest.kernel.kallsyms]  [g] print_tickdevice.isra.4                 [other]
-     0.10%     0.10%  :16031   [guest.kernel.kallsyms]  [g] kvm_save_sched_clock_state              [other]
-     0.09%     0.09%  :16031   [guest.kernel.kallsyms]  [g] sysfs_unbind_tick_dev                   [other]
-     0.09%     0.09%  :16029   [guest.kernel.kallsyms]  [g] __sched_setscheduler                    [other]
-     0.09%     0.09%  :16031   [guest.kernel.kallsyms]  [g] process_srcu                            [other]
-     0.08%     0.08%  :16031   [guest.kernel.kallsyms]  [g] avc_compute_av                          [other]
-     0.08%     0.08%  :16031   [guest.kernel.kallsyms]  [g] arch_remove_reservations                [other]
-     0.08%     0.08%  :16031   [guest.kernel.kallsyms]  [g] __switch_to_xtra                        [other]
-     0.08%     0.08%  :16031   [guest.kernel.kallsyms]  [g] __create_irqs                           [other]
-     0.08%     0.08%  :16031   [guest.kernel.kallsyms]  [g] ftrace_raw_output_irq_handler_exit      [other]
-     0.07%     0.07%  :16031   [guest.kernel.kallsyms]  [g] posix_clock_read                        [other]
-     0.07%     0.07%  :16031   [guest.kernel.kallsyms]  [g] posix_clock_poll                        [other]
-     0.07%     0.07%  :16031   [guest.kernel.kallsyms]  [g] native_cpu_up                           [other]
-     0.06%     0.06%  :16031   [guest.kernel.kallsyms]  [g] do_nmi                                  [other]
-     0.06%     0.06%  :16031   [guest.kernel.kallsyms]  [g] rcu_try_advance_all_cbs                 [other]
-     0.06%     0.06%  :16031   [guest.kernel.kallsyms]  [g] fat_msg                                 [other]
-     0.05%     0.05%  :16031   [guest.kernel.kallsyms]  [g] check_tsc_warp                          [other]
-     0.04%     0.04%  :16031   [guest.kernel.kallsyms]  [g] tick_handle_oneshot_broadcast           [other]
-     0.03%     0.03%  :16031   [guest.kernel.kallsyms]  [g] set_cpu_itimer                          [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] arp_ignore                              [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] store_powersave_bias_gov_sys            [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] cleanup_srcu_struct                     [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] create_prof_cpu_mask                    [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] alarm_timer_nsleep                      [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] time_cpufreq_notifier                   [other]
-     0.02%     0.02%  :16030   [guest.kernel.kallsyms]  [g] ftrace_raw_output_itimer_state          [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] tick_check_new_device                   [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] init_timer_key                          [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] tick_setup_device                       [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] clockevents_register_device             [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] __srcu_read_unlock                      [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] hpet_rtc_interrupt                      [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] init_srcu_struct                        [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] irq_spurious_proc_show                  [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] rcu_jiffies_till_stall_check            [other]
-     0.02%     0.02%  :16031   [guest.kernel.kallsyms]  [g] ksoftirqd_should_run                    [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] ftrace_raw_output_irq_handler_entry     [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] avc_denied.isra.0                       [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] __fat_fs_error                          [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] wakeme_after_rcu                        [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] prof_cpu_mask_proc_write                [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] srcu_barrier                            [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] tick_get_device                         [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] irq_domain_add_simple                   [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] synchronize_srcu_expedited              [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] sysfs_show_current_tick_dev             [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] tick_is_oneshot_available               [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] tick_check_replacement                  [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] clockevents_notify                      [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] show_stack                              [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] debug_kfree                             [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] tick_do_broadcast.constprop.6           [other]
-     0.01%     0.01%  :16031   [guest.kernel.kallsyms]  [g] sock_rps_save_rxhash.isra.28.part.29    [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] store_ignore_nice_load.isra.3           [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] perf_trace_itimer_expire                [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] hrtick_start                            [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] parse_probe_arg                         [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] wakeup_softirqd                         [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] tick_install_replacement                [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] detach_if_pending                       [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] default_affinity_show                   [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] tick_do_periodic_broadcast              [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] ftrace_raw_output_softirq               [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] tasklet_kill                            [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] update_rq_clock                         [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] tasklet_init                            [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] arch_local_irq_enable                   [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] irq_affinity_proc_show                  [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] store_sampling_down_factor.isra.4       [other]
-     0.00%     0.00%  :16031   [guest.kernel.kallsyms]  [g] amd_get_subcaches                       [other]
-
-Also tried a `virsh restore` with the `--bypass-cache` option and ran a perf trace. Noticable is the different trace. See output below:
-
-# perf trace without filesystem cache:
-# To display the perf.data header info, please use --header/--header-only options.
-#
-#
-# Total Lost Samples: 0
-#
-# Samples: 1M of event 'cycles'
-# Event count (approx.): 798928823821
-#
-# Children      Self  Command  Shared Object            Symbol
-# ........  ........  .......  .......................  ..........................................
-#
-    25.32%    25.32%  :34335   [guest.kernel.kallsyms]  [g] ftrace_raw_output_hrtimer_init
-     9.55%     9.55%  :34334   [guest.kernel.kallsyms]  [g] do_sysfs_unregistration
-     5.83%     5.83%  :34335   [guest.kernel.kallsyms]  [g] ftrace_raw_output_timer_expire_entry
-     5.60%     5.60%  :34334   [guest.kernel.kallsyms]  [g] posix_cpu_clock_get
-     4.37%     4.37%  :34334   [guest.kernel.kallsyms]  [g] kvm_init_debugfs
-     4.30%     4.30%  :34334   [guest.kernel.kallsyms]  [g] fat_msg
-     3.63%     3.63%  :34334   [guest.kernel.kallsyms]  [g] match_token
-     3.44%     3.44%  :34334   [guest.kernel.kallsyms]  [g] load_balance
-     3.28%     3.28%  :34333   [guest.kernel.kallsyms]  [g] save_paranoid
-     2.25%     2.25%  :34334   [guest.kernel.kallsyms]  [g] kvm_pv_guest_cpu_reboot
-     2.19%     2.19%  :34335   [guest.kernel.kallsyms]  [g] ftrace_raw_output_hrtimer_expire_entry
-     1.89%     1.89%  :34334   [guest.kernel.kallsyms]  [g] sys_kcmp
-     1.73%     1.73%  :34336   [guest.kernel.kallsyms]  [g] kvm_init_debugfs
-     1.58%     1.58%  :34335   [guest.kernel.kallsyms]  [g] ftrace_raw_output_hrtimer_start
-     1.26%     1.26%  :34336   [guest.kernel.kallsyms]  [g] save_paranoid
-     1.09%     1.09%  :34333   [guest.kernel.kallsyms]  [g] kvm_init_debugfs
-     1.01%     1.01%  :34333   [unknown]                [u] 0x0000000000434c1b
-     0.94%     0.94%  :34336   [guest.kernel.kallsyms]  [g] tg_set_cfs_bandwidth
-     0.88%     0.88%  :34333   [guest.kernel.kallsyms]  [g] avc_denied.isra.0
-     0.87%     0.87%  :34336   [guest.kernel.kallsyms]  [g] kvm_pv_guest_cpu_reboot
-     0.73%     0.73%  :34333   [guest.kernel.kallsyms]  [g] kvm_pv_guest_cpu_reboot
-     0.68%     0.68%  :34336   [guest.kernel.kallsyms]  [g] kvm_cpu_notify
-     0.65%     0.65%  :34336   [guest.kernel.kallsyms]  [g] rcu_process_callbacks
-     0.57%     0.57%  :34333   [guest.kernel.kallsyms]  [g] paravirt_write_msr
-     0.56%     0.56%  :34333   [guest.kernel.kallsyms]  [g] avc_compute_av
-     0.40%     0.40%  :34334   [guest.kernel.kallsyms]  [g] __fat_fs_error
-     0.39%     0.39%  :34334   [guest.kernel.kallsyms]  [g] amd_get_mmconfig_range
-     0.39%     0.39%  :34335   [guest.kernel.kallsyms]  [g] ptrace_request
-     0.38%     0.38%  :34336   [guest.kernel.kallsyms]  [g] sys_kcmp
-     0.34%     0.34%  :34333   [guest.kernel.kallsyms]  [g] posix_cpu_nsleep_restart
-     0.32%     0.32%  :34336   [guest.kernel.kallsyms]  [g] do_sysfs_unregistration
-     0.31%     0.31%  :34336   [guest.kernel.kallsyms]  [g] console_unlock
-     0.30%     0.30%  :34334   [guest.kernel.kallsyms]  [g] kvm_save_sched_clock_state
-     0.29%     0.29%  :34334   [guest.kernel.kallsyms]  [g] parse_no_kvmclock
-     0.27%     0.27%  :34333   [guest.kernel.kallsyms]  [g] do_sysfs_unregistration
-     0.27%     0.27%  :34333   [guest.kernel.kallsyms]  [g] check_tsc_warp
-     0.26%     0.26%  :34333   [guest.kernel.kallsyms]  [g] ksoftirqd_should_run
-     0.26%     0.26%  :34336   [guest.kernel.kallsyms]  [g] paravirt_write_msr
-     0.26%     0.26%  :34333   [guest.kernel.kallsyms]  [g] amd_get_mmconfig_range
-     0.25%     0.25%  :34333   [guest.kernel.kallsyms]  [g] sys_kcmp
-     0.22%     0.22%  :34336   [guest.kernel.kallsyms]  [g] build_sched_domains
-     0.22%     0.22%  :34333   [guest.kernel.kallsyms]  [g] do_cpu_nanosleep
-     0.22%     0.22%  :34333   [guest.kernel.kallsyms]  [g] print_stack_trace
-     0.21%     0.21%  :34336   [guest.kernel.kallsyms]  [g] irq_node_proc_show
-     0.19%     0.19%  :34336   [guest.kernel.kallsyms]  [g] print_stack_trace
-     0.19%     0.19%  :34336   [guest.kernel.kallsyms]  [g] __srcu_read_lock
-     0.18%     0.18%  :34336   [guest.kernel.kallsyms]  [g] __synchronize_srcu
-     0.17%     0.17%  :34333   [guest.kernel.kallsyms]  [g] __create_irqs
-     0.17%     0.17%  :34336   [guest.kernel.kallsyms]  [g] do_cpu_nanosleep
-     0.17%     0.17%  :34336   [guest.kernel.kallsyms]  [g] amd_get_mmconfig_range
-     0.15%     0.15%  :34336   [guest.kernel.kallsyms]  [g] posix_cpu_nsleep_restart
-     0.14%     0.14%  :34333   [guest.kernel.kallsyms]  [g] rcu_process_callbacks
-     0.14%     0.14%  :34333   [guest.kernel.kallsyms]  [g] rcu_try_advance_all_cbs
-     0.13%     0.13%  :34336   [guest.kernel.kallsyms]  [g] parse_no_kvmclock
-     0.11%     0.11%  :34333   [guest.kernel.kallsyms]  [g] tasklet_init
-     0.11%     0.11%  :34336   [guest.kernel.kallsyms]  [g] process_srcu
-     0.11%     0.11%  :34336   [guest.kernel.kallsyms]  [g] kvm_save_sched_clock_state
-     0.11%     0.11%  :34333   [guest.kernel.kallsyms]  [g] sysfs_unbind_tick_dev
-     0.10%     0.10%  :34336   [guest.kernel.kallsyms]  [g] __switch_to_xtra
-     0.10%     0.10%  :34334   [guest.kernel.kallsyms]  [g] __sched_setscheduler
-     0.10%     0.10%  :34333   [guest.kernel.kallsyms]  [g] print_tickdevice.isra.4
-     0.10%     0.10%  :34336   [guest.kernel.kallsyms]  [g] sysfs_unbind_tick_dev
-     0.10%     0.10%  :34336   [guest.kernel.kallsyms]  [g] print_tickdevice.isra.4
-     0.10%     0.10%  :34336   [guest.kernel.kallsyms]  [g] posix_clock_read
-     0.09%     0.09%  :34333   [guest.kernel.kallsyms]  [g] parse_no_kvmclock
-     0.09%     0.09%  :34333   [guest.kernel.kallsyms]  [g] posix_clock_poll
-     0.09%     0.09%  :34336   [guest.kernel.kallsyms]  [g] __irq_domain_add
-     0.09%     0.09%  :34336   [guest.kernel.kallsyms]  [g] avc_compute_av
-     0.09%     0.09%  :34333   [guest.kernel.kallsyms]  [g] posix_clock_read
-     0.09%     0.09%  :34333   [guest.kernel.kallsyms]  [g] hpet_rtc_interrupt
-     0.09%     0.09%  :34336   [guest.kernel.kallsyms]  [g] __create_irqs
-     0.08%     0.08%  :34336   [guest.kernel.kallsyms]  [g] posix_clock_poll
-     0.08%     0.08%  :34336   [guest.kernel.kallsyms]  [g] rcu_try_advance_all_cbs
-     0.07%     0.07%  :34336   [guest.kernel.kallsyms]  [g] ftrace_raw_output_irq_handler_exit
-     0.07%     0.07%  :34336   [guest.kernel.kallsyms]  [g] arch_remove_reservations
-     0.07%     0.07%  :34333   [guest.kernel.kallsyms]  [g] native_cpu_up
-     0.07%     0.07%  :34336   [guest.kernel.kallsyms]  [g] native_cpu_up
-     0.07%     0.07%  :34336   [guest.kernel.kallsyms]  [g] check_tsc_warp
-     0.07%     0.07%  :34333   [guest.kernel.kallsyms]  [g] kvm_save_sched_clock_state
-     0.07%     0.07%  :34333   [guest.kernel.kallsyms]  [g] do_nmi
-     0.06%     0.06%  :34336   [guest.kernel.kallsyms]  [g] do_nmi
-     0.06%     0.06%  :34335   [guest.kernel.kallsyms]  [g] ftrace_raw_output_itimer_state
-     0.05%     0.05%  :34336   [guest.kernel.kallsyms]  [g] fat_msg
-     0.04%     0.04%  :34336   [guest.kernel.kallsyms]  [g] store_powersave_bias_gov_sys
-     0.04%     0.04%  :34336   [guest.kernel.kallsyms]  [g] tick_handle_oneshot_broadcast
-     0.04%     0.04%  :34336   [guest.kernel.kallsyms]  [g] set_cpu_itimer
-     0.04%     0.04%  :34336   [guest.kernel.kallsyms]  [g] cleanup_srcu_struct
-     0.03%     0.03%  :34336   [guest.kernel.kallsyms]  [g] __srcu_read_unlock
-     0.03%     0.03%  :34336   [guest.kernel.kallsyms]  [g] time_cpufreq_notifier
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] irq_spurious_proc_show
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] alarm_timer_nsleep
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] ksoftirqd_should_run
-     0.02%     0.02%  :34333   [guest.kernel.kallsyms]  [g] tg_set_cfs_bandwidth
-     0.02%     0.02%  :34333   [guest.kernel.kallsyms]  [g] create_prof_cpu_mask
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] create_prof_cpu_mask
-     0.02%     0.02%  :34333   [guest.kernel.kallsyms]  [g] fat_msg
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] tick_check_new_device
-     0.02%     0.02%  :34333   [guest.kernel.kallsyms]  [g] __switch_to_xtra
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] tick_setup_device
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] init_timer_key
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] rcu_jiffies_till_stall_check
-     0.02%     0.02%  :34333   [guest.kernel.kallsyms]  [g] ftrace_raw_output_irq_handler_exit
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] arp_ignore
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] clockevents_register_device
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] hpet_rtc_interrupt
-     0.02%     0.02%  :34336   [guest.kernel.kallsyms]  [g] init_srcu_struct
-     0.01%     0.01%  :34333   [guest.kernel.kallsyms]  [g] irq_node_proc_show
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] __fat_fs_error
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] tick_check_replacement
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] avc_denied.isra.0
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] tick_get_device
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] irq_affinity_proc_show
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] sysfs_show_current_tick_dev
-     0.01%     0.01%  :34333   [guest.kernel.kallsyms]  [g] __fat_fs_error
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] ftrace_raw_output_irq_handler_entry
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] tick_is_oneshot_available
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] irq_domain_add_simple
-     0.01%     0.01%  :34333   [guest.kernel.kallsyms]  [g] irq_spurious_proc_show
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] tick_do_broadcast.constprop.6
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] sock_rps_save_rxhash.isra.28.part.29
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] prof_cpu_mask_proc_write
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] perf_trace_itimer_expire
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] srcu_barrier
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] store_ignore_nice_load.isra.3
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] wakeme_after_rcu
-     0.01%     0.01%  :34333   [guest.kernel.kallsyms]  [g] ftrace_raw_output_irq_handler_entry
-     0.01%     0.01%  :34333   [guest.kernel.kallsyms]  [g] ftrace_raw_output_softirq
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] debug_kfree
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] clockevents_notify
-     0.01%     0.01%  :34336   [guest.kernel.kallsyms]  [g] parse_probe_arg
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] hrtick_start
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] detach_if_pending
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] tasklet_init
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] show_stack
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] wakeup_softirqd
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] arch_local_irq_enable
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] tasklet_kill
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] default_affinity_show
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] ftrace_raw_output_softirq
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] store_sampling_down_factor.isra.4
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] synchronize_srcu_expedited
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] update_rq_clock
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] tick_do_periodic_broadcast
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] tick_install_replacement
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] amd_get_subcaches
-     0.00%     0.00%  :34334   [guest.kernel.kallsyms]  [g] amd_get_subcaches
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] tick_handle_periodic
-     0.00%     0.00%  :34336   [guest.kernel.kallsyms]  [g] __page_cache_alloc
-
-I am not sure how correct the symbol mapping of perf is, so I don't know if this is usable at all.
-
-I have dumped info registers with the `qemu-monitor-command` command after the  migration problematic VM and this gave the following output:
-
-RAX=0000000000001975 RBX=ffff8802342fc000 RCX=000000000000beac RDX=000000000000beaa
-RSI=000000000000beac RDI=ffff8802342fc000 RBP=ffff880233d3fb18 RSP=ffff880233d3fb18
-R8 =0000000000000286 R9 =ffff8800a71eee40 R10=ffff8800a71eeed4 R11=000000000000000a
-R12=ffff8802342fc000 R13=ffffffff81cdf010 R14=ffff880233d3fb58 R15=ffff88003672b200
-RIP=ffffffff817360b7 RFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
-ES =0000 0000000000000000 000fffff 00000000
-CS =0010 0000000000000000 ffffffff 00a09b00 DPL=0 CS64 [-RA]
-SS =0018 0000000000000000 ffffffff 00c09300 DPL=0 DS   [-WA]
-DS =0000 0000000000000000 000fffff 00000000
-FS =0000 0000000000000000 000fffff 00000000
-GS =0000 ffff88023fc00000 000fffff 00000000
-LDT=0000 0000000000000000 000fffff 00000000
-TR =0040 ffff88023fc04440 00002087 00008b00 DPL=0 TSS64-busy
-GDT=     ffff88023fc0c000 0000007f
-IDT=     ffffffffff576000 00000fff
-CR0=8005003b CR2=0000000000408950 CR3=0000000232098000 CR4=00000670
-DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
-DR6=00000000ffff0ff0 DR7=0000000000000400
-EFER=0000000000000d01
-FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001fa0
-FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
-FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
-FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
-FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
-XMM00=ffffffffff0000ff0000000000000000 XMM01=0000010101000000ffffffffffffffff
-XMM02=00007fe302de17006776615f64616f6c XMM03=00000000000000000000000000000000
-XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000ff0000
-XMM06=5b5b5b5b5b5b5b5b5b5b5b5b5b5b5b5b XMM07=20202020202020202020202020202020
-XMM08=00000000000000000000000000000000 XMM09=00000000000000000000000000000000
-XMM10=00000000000000000000000000000000 XMM11=00000000000000000000000000000000
-XMM12=00ff000000ff0000000000000000ff00 XMM13=00000000000000000000000000000000
-XMM14=00000000000000000000000000000000 XMM15=00000000000000000000000000000000
-
-And I looped this for a minute to check were the RIP is changing to:
-136 RIP=0000000000434c1b
-173 RIP=ffffffff8105144a
-  2 RIP=ffffffff810521ff
-  1 RIP=ffffffff81070816
-
-
-I tried to reproduce this with some manual actions prior to migrating between qemu 2.6.2 and 2.11.1 on our testing environment using similar hardware (56 core model name: Intel(R) Xeon(R) Gold 6126 CPU @ 2.60GHz)
-And I was not able to reproduce this, i tried the following:
-- restore without filesystem caches (see new perf traces below)
-- create vm with same kernel as stuck vm
-- restore paused detach net device and virtio block device (detach doesn't work)
-- try to do a lot of network and disk io while migrating
-- ecrypt fs actions during migration
-- migrate 4000 times between 2.6.2 -> 2.11 using loop
-- add extra timer calls inside guest for migrate loop (done using cyclictest)
-- try with guest kernel 3.13.0-145-generic, same kernel vm was running with this issue
-- try host clock/timer calls on 2.11.1 host prior and during migration bound on first cpu core (cyclictest -a 0 -c 1 -d 200 -H -l 1 -t 2)
-
-I asked the vm owner what he is doing on his vm, and he told me that he is using 80% of his mem around 14G of the 16G, the vm is running a tomcat 7 server and a libreoffice deamon the vm has a load of 1.0 and runs Ubuntu 14.04 with kernel 3.13.0-145.
-
-The other vms were running centos 6, centos 7, debian 7, debian 8, ubuntu 13.10, ubuntu 14.04, ubuntu 12.04 the majority of these vms are running linux kernel 3.*.
-
-The thing is I am actually out of ideas for reproducing this, and I am not sure how to pinpoint this issue, I would like some help and possible some extra tips on debugging.
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