L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
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WARNING: CPU: 0 PID: 8091 at arch/x86/kvm/vmx.c:4719 free_loaded_vmcs arch/x86/kvm/vmx.c:4719 [inline]
WARNING: CPU: 0 PID: 8091 at arch/x86/kvm/vmx.c:4719 free_loaded_vmcs.cold+0x11/0x18 arch/x86/kvm/vmx.c:4710
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 8091 Comm: syz-executor330 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 panic+0x26a/0x50e kernel/panic.c:186
 __warn.cold+0x20/0x5a kernel/panic.c:541
 report_bug+0x262/0x2b0 lib/bug.c:183
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 fixup_bug arch/x86/kernel/traps.c:173 [inline]
 do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:free_loaded_vmcs arch/x86/kvm/vmx.c:4719 [inline]
RIP: 0010:free_loaded_vmcs.cold+0x11/0x18 arch/x86/kvm/vmx.c:4710
Code: ee 48 c7 c7 80 d1 63 88 c6 05 07 d4 34 03 01 e8 fc c4 01 00 e9 30 4b 27 f9 e8 87 93 70 f9 48 c7 c7 e0 c5 63 88 e8 e6 c4 01 00 <0f> 0b e9 13 7e 27 f9 e8 6f 93 70 f9 48 c7 c7 e0 c5 63 88 e8 ce c4
RSP: 0018:ffff8880956df928 EFLAGS: 00010282
RAX: 0000000000000024 RBX: ffff8880924ed768 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff814dff01 RDI: ffffed1012adbf17
RBP: ffff8880ab2e3000 R08: 0000000000000024 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8880924ed768 R14: 0000000000000003 R15: ffff8880924e8040
 vmx_free_vcpu+0x1a9/0x320 arch/x86/kvm/vmx.c:11059
 kvm_arch_vcpu_free arch/x86/kvm/x86.c:8650 [inline]
 kvm_free_vcpus arch/x86/kvm/x86.c:9105 [inline]
 kvm_arch_destroy_vm+0x2f6/0x600 arch/x86/kvm/x86.c:9207
 kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:810 [inline]
 kvm_put_kvm+0x457/0xc70 arch/x86/kvm/../../../virt/kvm/kvm_main.c:831
 kvm_vm_release+0x3f/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:842
 __fput+0x2ce/0x890 fs/file_table.c:278
 task_work_run+0x148/0x1c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xbf3/0x2be0 kernel/exit.c:870
 do_group_exit+0x125/0x310 kernel/exit.c:967
 get_signal+0x3f2/0x1f70 kernel/signal.c:2589
 do_signal+0x8f/0x1670 arch/x86/kernel/signal.c:799
 exit_to_usermode_loop+0x204/0x2a0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
 do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f0653de1729
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0653d91308 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f0653e6a408 RCX: 00007f0653de1729
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f0653e6a408
RBP: 00007f0653e6a400 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f0653e6a40c
R13: 00007f0653e370b8 R14: 6d766b2f7665642f R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..