Re: [syzbot] possible deadlock in scheduler_tick

From: Wanpeng Li
Date: Wed Mar 24 2021 - 07:35:58 EST

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In reply to: syzbot: "[syzbot] possible deadlock in scheduler_tick"
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Cc David Woodhouse,
On Wed, 24 Mar 2021 at 18:11, syzbot
<syzbot+b282b65c2c68492df769@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 1c273e10 Merge tag 'zonefs-5.12-rc4' of git://git.kernel.o..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13c0414ed00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=6abda3336c698a07
> dashboard link: https://syzkaller.appspot.com/bug?extid=b282b65c2c68492df769
> userspace arch: i386
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17d86ad6d00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17b8497cd00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b282b65c2c68492df769@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> =====================================================
> WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
> 5.12.0-rc3-syzkaller #0 Not tainted
> -----------------------------------------------------
> syz-executor030/8435 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
> ffffc90001a2a230 (&kvm->arch.pvclock_gtod_sync_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
> ffffc90001a2a230 (&kvm->arch.pvclock_gtod_sync_lock){+.+.}-{2:2}, at: get_kvmclock_ns+0x25/0x390 arch/x86/kvm/x86.c:2587
>
> and this task is already holding:
> ffff8880b9d35198 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1321 [inline]
> ffff8880b9d35198 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x21c/0x21b0 kernel/sched/core.c:4990
> which would create a new lock dependency:
> (&rq->lock){-.-.}-{2:2} -> (&kvm->arch.pvclock_gtod_sync_lock){+.+.}-{2:2}
>
> but this new dependency connects a HARDIRQ-irq-safe lock:
> (&rq->lock){-.-.}-{2:2}
>
> ... which became HARDIRQ-irq-safe at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> rq_lock kernel/sched/sched.h:1321 [inline]
> scheduler_tick+0xa4/0x4b0 kernel/sched/core.c:4538
> update_process_times+0x191/0x200 kernel/time/timer.c:1801
> tick_periodic+0x79/0x230 kernel/time/tick-common.c:100
> tick_handle_periodic+0x41/0x120 kernel/time/tick-common.c:112
> timer_interrupt+0x3f/0x60 arch/x86/kernel/time.c:57
> __handle_irq_event_percpu+0x303/0x8f0 kernel/irq/handle.c:156
> handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
> handle_irq_event+0x102/0x290 kernel/irq/handle.c:213
> handle_level_irq+0x256/0x6e0 kernel/irq/chip.c:650
> generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
> handle_irq arch/x86/kernel/irq.c:231 [inline]
> __common_interrupt+0x9e/0x200 arch/x86/kernel/irq.c:250
> common_interrupt+0x9f/0xd0 arch/x86/kernel/irq.c:240
> asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:623
> __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
> _raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:191
> __setup_irq+0xc72/0x1ce0 kernel/irq/manage.c:1737
> request_threaded_irq+0x28a/0x3b0 kernel/irq/manage.c:2127
> request_irq include/linux/interrupt.h:160 [inline]
> setup_default_timer_irq arch/x86/kernel/time.c:70 [inline]
> hpet_time_init+0x28/0x42 arch/x86/kernel/time.c:82
> x86_late_time_init+0x58/0x94 arch/x86/kernel/time.c:94
> start_kernel+0x3ee/0x496 init/main.c:1028
> secondary_startup_64_no_verify+0xb0/0xbb
>
> to a HARDIRQ-irq-unsafe lock:
> (&kvm->arch.pvclock_gtod_sync_lock){+.+.}-{2:2}
>
> ... which became HARDIRQ-irq-unsafe at:
> ...
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:354 [inline]
> kvm_synchronize_tsc+0x459/0x1230 arch/x86/kvm/x86.c:2332
> kvm_arch_vcpu_postcreate+0x73/0x180 arch/x86/kvm/x86.c:10183
> kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3239 [inline]
> kvm_vm_ioctl+0x1b2d/0x2800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3839
> kvm_vm_compat_ioctl+0x125/0x230 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4052
> __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
> do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline]
> __do_fast_syscall_32+0x56/0x90 arch/x86/entry/common.c:140
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
>
> other info that might help us debug this:
>
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&kvm->arch.pvclock_gtod_sync_lock);
> local_irq_disable();
> lock(&rq->lock);
> lock(&kvm->arch.pvclock_gtod_sync_lock);
> <Interrupt>
> lock(&rq->lock);
>

The offender is get_kvmclock_ns() which is called in the context
switch process. The bad commit is 30b5c851af7991ad0 ("KVM: x86/xen:
Add support for vCPU runstate information").

> *** DEADLOCK ***
>
> 1 lock held by syz-executor030/8435:
> #0: ffff8880b9d35198 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1321 [inline]
> #0: ffff8880b9d35198 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x21c/0x21b0 kernel/sched/core.c:4990
>
> the dependencies between HARDIRQ-irq-safe lock and the holding lock:
> -> (&rq->lock){-.-.}-{2:2} {
> IN-HARDIRQ-W at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> rq_lock kernel/sched/sched.h:1321 [inline]
> scheduler_tick+0xa4/0x4b0 kernel/sched/core.c:4538
> update_process_times+0x191/0x200 kernel/time/timer.c:1801
> tick_periodic+0x79/0x230 kernel/time/tick-common.c:100
> tick_handle_periodic+0x41/0x120 kernel/time/tick-common.c:112
> timer_interrupt+0x3f/0x60 arch/x86/kernel/time.c:57
> __handle_irq_event_percpu+0x303/0x8f0 kernel/irq/handle.c:156
> handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
> handle_irq_event+0x102/0x290 kernel/irq/handle.c:213
> handle_level_irq+0x256/0x6e0 kernel/irq/chip.c:650
> generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
> handle_irq arch/x86/kernel/irq.c:231 [inline]
> __common_interrupt+0x9e/0x200 arch/x86/kernel/irq.c:250
> common_interrupt+0x9f/0xd0 arch/x86/kernel/irq.c:240
> asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:623
> __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
> _raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:191
> __setup_irq+0xc72/0x1ce0 kernel/irq/manage.c:1737
> request_threaded_irq+0x28a/0x3b0 kernel/irq/manage.c:2127
> request_irq include/linux/interrupt.h:160 [inline]
> setup_default_timer_irq arch/x86/kernel/time.c:70 [inline]
> hpet_time_init+0x28/0x42 arch/x86/kernel/time.c:82
> x86_late_time_init+0x58/0x94 arch/x86/kernel/time.c:94
> start_kernel+0x3ee/0x496 init/main.c:1028
> secondary_startup_64_no_verify+0xb0/0xbb
> IN-SOFTIRQ-W at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> rq_lock kernel/sched/sched.h:1321 [inline]
> ttwu_queue kernel/sched/core.c:3184 [inline]
> try_to_wake_up+0x5e6/0x14a0 kernel/sched/core.c:3464
> call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1431
> expire_timers kernel/time/timer.c:1476 [inline]
> __run_timers.part.0+0x67c/0xa50 kernel/time/timer.c:1745
> __run_timers kernel/time/timer.c:1726 [inline]
> run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1758
> __do_softirq+0x29b/0x9f6 kernel/softirq.c:345
> invoke_softirq kernel/softirq.c:221 [inline]
> __irq_exit_rcu kernel/softirq.c:422 [inline]
> irq_exit_rcu+0x134/0x200 kernel/softirq.c:434
> sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1100
> asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
> rdtsc_ordered arch/x86/include/asm/msr.h:234 [inline]
> delay_tsc+0x45/0xb0 arch/x86/lib/delay.c:72
> try_check_zero+0x223/0x430 kernel/rcu/srcutree.c:707
> srcu_advance_state kernel/rcu/srcutree.c:1229 [inline]
> process_srcu+0x2f2/0xe90 kernel/rcu/srcutree.c:1327
> process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
> worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
> kthread+0x3b1/0x4a0 kernel/kthread.c:292
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
> INITIAL USE at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
> rq_attach_root+0x20/0x2e0 kernel/sched/topology.c:470
> sched_init+0x6e8/0xbf3 kernel/sched/core.c:8213
> start_kernel+0x18e/0x496 init/main.c:920
> secondary_startup_64_no_verify+0xb0/0xbb
> }
> ... key at: [<ffffffff8f39a7c0>] __key.298+0x0/0x40
> ... acquired at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:354 [inline]
> get_kvmclock_ns+0x25/0x390 arch/x86/kvm/x86.c:2587
> kvm_xen_update_runstate+0x3d/0x2c0 arch/x86/kvm/xen.c:69
> kvm_xen_update_runstate_guest+0x74/0x320 arch/x86/kvm/xen.c:100
> kvm_xen_runstate_set_preempted arch/x86/kvm/xen.h:96 [inline]
> kvm_arch_vcpu_put+0x2d8/0x5a0 arch/x86/kvm/x86.c:4062
> kvm_sched_out+0xbf/0x100 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4876
> __fire_sched_out_preempt_notifiers kernel/sched/core.c:3922 [inline]
> fire_sched_out_preempt_notifiers kernel/sched/core.c:3930 [inline]
> prepare_task_switch kernel/sched/core.c:4126 [inline]
> context_switch kernel/sched/core.c:4274 [inline]
> __schedule+0xfd0/0x21b0 kernel/sched/core.c:5073
> preempt_schedule_irq+0x4e/0x90 kernel/sched/core.c:5530
> irqentry_exit_cond_resched kernel/entry/common.c:392 [inline]
> irqentry_exit_cond_resched kernel/entry/common.c:384 [inline]
> irqentry_exit+0x7a/0xa0 kernel/entry/common.c:428
> asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
> __vmcs_writel arch/x86/kvm/vmx/vmx_ops.h:176 [inline]
> vmcs_write16 arch/x86/kvm/vmx/vmx_ops.h:185 [inline]
> seg_setup+0x66/0x2a0 arch/x86/kvm/vmx/vmx.c:3633
> vmx_vcpu_reset+0x20a/0xee0 arch/x86/kvm/vmx/vmx.c:4455
> kvm_arch_vcpu_create+0x765/0xbb0 arch/x86/kvm/x86.c:10152
> kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3201 [inline]
> kvm_vm_ioctl+0x1702/0x2800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3839
> kvm_vm_compat_ioctl+0x125/0x230 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4052
> __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
> do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline]
> __do_fast_syscall_32+0x56/0x90 arch/x86/entry/common.c:140
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
>
>
> the dependencies between the lock to be acquired
> and HARDIRQ-irq-unsafe lock:
> -> (&kvm->arch.pvclock_gtod_sync_lock){+.+.}-{2:2} {
> HARDIRQ-ON-W at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:354 [inline]
> kvm_synchronize_tsc+0x459/0x1230 arch/x86/kvm/x86.c:2332
> kvm_arch_vcpu_postcreate+0x73/0x180 arch/x86/kvm/x86.c:10183
> kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3239 [inline]
> kvm_vm_ioctl+0x1b2d/0x2800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3839
> kvm_vm_compat_ioctl+0x125/0x230 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4052
> __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
> do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline]
> __do_fast_syscall_32+0x56/0x90 arch/x86/entry/common.c:140
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> SOFTIRQ-ON-W at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:354 [inline]
> kvm_synchronize_tsc+0x459/0x1230 arch/x86/kvm/x86.c:2332
> kvm_arch_vcpu_postcreate+0x73/0x180 arch/x86/kvm/x86.c:10183
> kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3239 [inline]
> kvm_vm_ioctl+0x1b2d/0x2800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3839
> kvm_vm_compat_ioctl+0x125/0x230 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4052
> __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
> do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline]
> __do_fast_syscall_32+0x56/0x90 arch/x86/entry/common.c:140
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> INITIAL USE at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:354 [inline]
> kvm_synchronize_tsc+0x459/0x1230 arch/x86/kvm/x86.c:2332
> kvm_arch_vcpu_postcreate+0x73/0x180 arch/x86/kvm/x86.c:10183
> kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3239 [inline]
> kvm_vm_ioctl+0x1b2d/0x2800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3839
> kvm_vm_compat_ioctl+0x125/0x230 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4052
> __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
> do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline]
> __do_fast_syscall_32+0x56/0x90 arch/x86/entry/common.c:140
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> }
> ... key at: [<ffffffff8f371000>] __key.4+0x0/0x40
> ... acquired at:
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:354 [inline]
> get_kvmclock_ns+0x25/0x390 arch/x86/kvm/x86.c:2587
> kvm_xen_update_runstate+0x3d/0x2c0 arch/x86/kvm/xen.c:69
> kvm_xen_update_runstate_guest+0x74/0x320 arch/x86/kvm/xen.c:100
> kvm_xen_runstate_set_preempted arch/x86/kvm/xen.h:96 [inline]
> kvm_arch_vcpu_put+0x2d8/0x5a0 arch/x86/kvm/x86.c:4062
> kvm_sched_out+0xbf/0x100 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4876
> __fire_sched_out_preempt_notifiers kernel/sched/core.c:3922 [inline]
> fire_sched_out_preempt_notifiers kernel/sched/core.c:3930 [inline]
> prepare_task_switch kernel/sched/core.c:4126 [inline]
> context_switch kernel/sched/core.c:4274 [inline]
> __schedule+0xfd0/0x21b0 kernel/sched/core.c:5073
> preempt_schedule_irq+0x4e/0x90 kernel/sched/core.c:5530
> irqentry_exit_cond_resched kernel/entry/common.c:392 [inline]
> irqentry_exit_cond_resched kernel/entry/common.c:384 [inline]
> irqentry_exit+0x7a/0xa0 kernel/entry/common.c:428
> asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
> __vmcs_writel arch/x86/kvm/vmx/vmx_ops.h:176 [inline]
> vmcs_write16 arch/x86/kvm/vmx/vmx_ops.h:185 [inline]
> seg_setup+0x66/0x2a0 arch/x86/kvm/vmx/vmx.c:3633
> vmx_vcpu_reset+0x20a/0xee0 arch/x86/kvm/vmx/vmx.c:4455
> kvm_arch_vcpu_create+0x765/0xbb0 arch/x86/kvm/x86.c:10152
> kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3201 [inline]
> kvm_vm_ioctl+0x1702/0x2800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3839
> kvm_vm_compat_ioctl+0x125/0x230 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4052
> __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
> do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline]
> __do_fast_syscall_32+0x56/0x90 arch/x86/entry/common.c:140
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
>
>
> stack backtrace:
> CPU: 1 PID: 8435 Comm: syz-executor030 Not tainted 5.12.0-rc3-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:79 [inline]
> dump_stack+0x141/0x1d7 lib/dump_stack.c:120
> print_bad_irq_dependency kernel/locking/lockdep.c:2460 [inline]
> check_irq_usage.cold+0x50d/0x744 kernel/locking/lockdep.c:2689
> check_prev_add kernel/locking/lockdep.c:2940 [inline]
> check_prevs_add kernel/locking/lockdep.c:3059 [inline]
> validate_chain kernel/locking/lockdep.c:3674 [inline]
> __lock_acquire+0x2b2c/0x54c0 kernel/locking/lockdep.c:4900
> lock_acquire kernel/locking/lockdep.c:5510 [inline]
> lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:354 [inline]
> get_kvmclock_ns+0x25/0x390 arch/x86/kvm/x86.c:2587
> kvm_xen_update_runstate+0x3d/0x2c0 arch/x86/kvm/xen.c:69
> kvm_xen_update_runstate_guest+0x74/0x320 arch/x86/kvm/xen.c:100
> kvm_xen_runstate_set_preempted arch/x86/kvm/xen.h:96 [inline]
> kvm_arch_vcpu_put+0x2d8/0x5a0 arch/x86/kvm/x86.c:4062
> kvm_sched_out+0xbf/0x100 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4876
> __fire_sched_out_preempt_notifiers kernel/sched/core.c:3922 [inline]
> fire_sched_out_preempt_notifiers kernel/sched/core.c:3930 [inline]
> prepare_task_switch kernel/sched/core.c:4126 [inline]
> context_switch kernel/sched/core.c:4274 [inline]
> __schedule+0xfd0/0x21b0 kernel/sched/core.c:5073
> preempt_schedule_irq+0x4e/0x90 kernel/sched/core.c:5530
> irqentry_exit_cond_resched kernel/entry/common.c:392 [inline]
> irqentry_exit_cond_resched kernel/entry/common.c:384 [inline]
> irqentry_exit+0x7a/0xa0 kernel/entry/common.c:428
> asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
> RIP: 0010:__vmcs_writel arch/x86/kvm/vmx/vmx_ops.h:176 [inline]
> RIP: 0010:vmcs_write16 arch/x86/kvm/vmx/vmx_ops.h:185 [inline]
> RIP: 0010:seg_setup+0x66/0x2a0 arch/x86/kvm/vmx/vmx.c:3633
> Code: 84 c0 74 08 3c 03 0f 8e 32 02 00 00 48 89 d8 48 c1 e0 04 44 8b a0 80 72 64 89 0f 1f 44 00 00 e8 d0 31 56 00 31 c0 44 0f 79 e0 <2e> 0f 86 db 01 00 00 e8 be 31 56 00 e8 b9 31 56 00 48 89 df 48 b8
> RSP: 0018:ffffc9000183f988 EFLAGS: 00000202
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff88801ba39c40 RSI: ffffffff811db9b0 RDI: ffffffff89647280
> RBP: 0000000000000000 R08: 0000000000000001 R09: ffffc90001a2a16b
> R10: ffffffff811dba9b R11: 0000000000000000 R12: 0000000000000800
> R13: 1ffff92000307f35 R14: ffff88801755e170 R15: 0000000000000040
> vmx_vcpu_reset+0x20a/0xee0 arch/x86/kvm/vmx/vmx.c:4455
> kvm_arch_vcpu_create+0x765/0xbb0 arch/x86/kvm/x86.c:10152
> kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3201 [inline]
> kvm_vm_ioctl+0x1702/0x2800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3839
> kvm_vm_compat_ioctl+0x125/0x230 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4052
> __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
> do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline]
> __do_fast_syscall_32+0x56/0x90 arch/x86/entry/common.c:140
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> RIP: 0023:0xf7f50549
> Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> RSP: 002b:00000000ffce641c EFLAGS: 00000217 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000000ae41
> RDX: 0000000000000000 RSI: 0000000000000036 RDI: 0000000000000004
> RBP: 000000004038ae7a R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches

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