syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 ticks this GP) idle=b66/1/0x4000000000000004 softirq=28179/28180 fqs=1 
	(t=29639 jiffies g=24749 q=37154)
NMI backtrace for cpu 1
CPU: 1 PID: 16869 Comm: syz-executor.5 Not tainted 5.3.0-rc2-next-20190801 #57
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x183/0x1cf kernel/rcu/tree_stall.h:254
 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:529 [inline]
 rcu_pending kernel/rcu/tree.c:2736 [inline]
 rcu_sched_clock_irq.cold+0x4dd/0xc13 kernel/rcu/tree.c:2183
 update_process_times+0x32/0x80 kernel/time/timer.c:1724
 tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:167
 tick_sched_timer+0x53/0x140 kernel/time/tick-sched.c:1299
 __run_hrtimer kernel/time/hrtimer.c:1493 [inline]
 __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1555
 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1617
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1068 [inline]
 smp_apic_timer_interrupt+0x160/0x610 arch/x86/kernel/apic/apic.c:1093
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:828
RIP: 0010:ffs arch/x86/include/asm/bitops.h:297 [inline]
RIP: 0010:__do_softirq+0x227/0x98c kernel/softirq.c:280
Code: c7 c0 b0 f4 d2 88 48 c1 e8 03 42 80 3c 30 00 0f 85 b1 06 00 00 48 83 3d 96 f2 72 01 00 0f 84 d6 05 00 00 fb 66 0f 1f 44 00 00 <b8> ff ff ff ff 48 c7 45 c8 00 91 c0 88 0f bc 45 d4 83 c0 01 89 45
RSP: 0018:ffff8880ae909f18 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11a5e96 RBX: ffff88809aa061c0 RCX: 1ffffffff134c0be
RDX: 0000000000000000 RSI: ffffffff8177a50e RDI: ffffffff876001fc
RBP: ffff8880ae909f98 R08: ffff88809aa061c0 R09: 0000000000000000
R10: ffffffff89e49050 R11: 0000000000000001 R12: ffff888099137938
R13: 0000000000000028 R14: dffffc0000000000 R15: 0000000000000000
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x19b/0x1e0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 do_IRQ+0x12c/0x200 arch/x86/kernel/irq.c:259
 common_interrupt+0xf/0xf arch/x86/entry/entry_64.S:605
 </IRQ>
RIP: 0010:variable_test_bit arch/x86/include/asm/bitops.h:214 [inline]
RIP: 0010:test_bit include/asm-generic/bitops-instrumented.h:238 [inline]
RIP: 0010:kvm_test_request include/linux/kvm_host.h:1207 [inline]
RIP: 0010:kvm_check_request+0x30/0x70 include/linux/kvm_host.h:1217
Code: 41 55 41 54 49 89 f4 53 4d 8d 74 24 30 89 fb e8 f6 13 67 00 be 08 00 00 00 4c 89 f7 0f b6 db e8 36 e2 a1 00 49 0f a3 5c 24 30 <41> 0f 92 c5 31 ff 44 89 ee e8 12 15 67 00 45 84 ed 75 11 e8 c8 13
RSP: 0018:ffff8880991379e0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffd7
RAX: 0000000000000001 RBX: 000000000000001f RCX: ffffffff810b0e4a
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff888093c409f0
RBP: ffff888099137a00 R08: 1ffff1101278813e R09: ffffed101278813f
R10: ffffed101278813e R11: ffff888093c409f7 R12: ffff888093c409c0
R13: ffff888093c409c0 R14: ffff888093c409f0 R15: ffff888093c409f0
 vcpu_enter_guest+0x32a6/0x5e90 arch/x86/kvm/x86.c:7866
 vcpu_run arch/x86/kvm/x86.c:8151 [inline]
 kvm_arch_vcpu_ioctl_run+0x464/0x1750 arch/x86/kvm/x86.c:8359
 kvm_vcpu_ioctl+0x4dc/0xfd0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2754
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fa754e29c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa754e2a6d4
R13: 00000000004c2bcf R14: 00000000004d6150 R15: 00000000ffffffff