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BUG: KCSAN: data-race in pvclock_gtod_notify / pvclock_update_vm_gtod_copy

write to 0xffffffff85fdd628 of 4 bytes by interrupt on cpu 0:
 update_pvclock_gtod arch/x86/kvm/x86.c:1552 [inline]
 pvclock_gtod_notify+0xa4/0x260 arch/x86/kvm/x86.c:7126
 notifier_call_chain+0xd7/0x160 kernel/notifier.c:95
 __raw_notifier_call_chain kernel/notifier.c:396 [inline]
 raw_notifier_call_chain+0x37/0x50 kernel/notifier.c:403
 update_pvclock_gtod kernel/time/timekeeping.c:578 [inline]
 timekeeping_update+0x1b5/0x2d0 kernel/time/timekeeping.c:672
 timekeeping_advance+0x882/0xd80 kernel/time/timekeeping.c:2120
 update_wall_time+0x19/0x20 kernel/time/timekeeping.c:2137
 tick_do_update_jiffies64+0x1ae/0x260 kernel/time/tick-sched.c:94
 tick_sched_do_timer+0xd4/0xe0 kernel/time/tick-sched.c:138
 tick_sched_timer+0x43/0xe0 kernel/time/tick-sched.c:1292
 __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
 __hrtimer_run_queues+0x288/0x600 kernel/time/hrtimer.c:1576
 hrtimer_interrupt+0x22a/0x480 kernel/time/hrtimer.c:1638
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0xdc/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 check_kcov_mode kernel/kcov.c:68 [inline]
 write_comp_data+0x17/0x70 kernel/kcov.c:123

read to 0xffffffff85fdd628 of 4 bytes by task 10356 on cpu 1:
 arch_atomic_set arch/x86/include/asm/atomic.h:43 [inline]
 atomic_set include/asm-generic/atomic-instrumented.h:58 [inline]
 pvclock_update_vm_gtod_copy+0x4a7/0x4d0 arch/x86/kvm/x86.c:2149
 kvm_gen_update_masterclock+0x5f/0x1c0 arch/x86/kvm/x86.c:2172
 vcpu_enter_guest+0x1609/0x3820 arch/x86/kvm/x86.c:7951
 vcpu_run arch/x86/kvm/x86.c:8290 [inline]
 kvm_arch_vcpu_ioctl_run+0x2a2/0xdc0 arch/x86/kvm/x86.c:8497
 kvm_vcpu_ioctl+0x752/0xa30 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2765
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x991/0xc60 fs/ioctl.c:696
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:718
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10356 Comm: syz-executor.4 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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