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.
kvm: emulating exchange as write
------------[ cut here ]------------
WARNING: CPU: 1 PID: 8107 at arch/x86/kvm/x86.c:8095 kvm_arch_vcpu_ioctl_run.cold+0x11/0x48 arch/x86/kvm/x86.c:8095
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 8107 Comm: syz-executor115 Not tainted 4.19.196-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:kvm_arch_vcpu_ioctl_run.cold+0x11/0x48 arch/x86/kvm/x86.c:8095
Code: d8 1b f9 e8 a1 7c 71 f9 48 c7 c7 80 3d 62 88 e8 7b d9 01 00 e9 50 e9 1b f9 e8 8b 7c 71 f9 48 c7 c7 20 23 62 88 e8 65 d9 01 00 <0f> 0b e9 7d 29 1c f9 e8 73 7c 71 f9 48 c7 c7 20 23 62 88 e8 4d d9
RSP: 0018:ffff888095397a10 EFLAGS: 00010286
RAX: 0000000000000024 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff814dfc91 RDI: ffffed1012a72f34
RBP: ffff888095397bb0 R08: 0000000000000024 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: ffff888098ddc000
R13: 0000000000000000 R14: ffff8880a4819100 R15: ffff8880a15a0040
 kvm_vcpu_ioctl+0x493/0xe10 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2822
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x447589
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:00007f34c07da308 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004cd438 RCX: 0000000000447589
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 00000000004cd430 R08: 00007f34c07da700 R09: 0000000000000000
R10: 00007f34c07da700 R11: 0000000000000246 R12: 00000000004cd43c
R13: 000000000049c0b8 R14: 6d766b2f7665642f R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..