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: 7969 at arch/x86/kvm/x86.c:7534 kvm_arch_vcpu_ioctl_run+0x145/0x5c80 arch/x86/kvm/x86.c:7534
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 7969 Comm: syz-executor260 Not tainted 4.14.244-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 panic+0x1f9/0x42d kernel/panic.c:183
 __warn.cold+0x20/0x44 kernel/panic.c:547
 report_bug+0x208/0x250 lib/bug.c:183
 fixup_bug arch/x86/kernel/traps.c:177 [inline]
 fixup_bug arch/x86/kernel/traps.c:172 [inline]
 do_error_trap+0x195/0x2d0 arch/x86/kernel/traps.c:295
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:kvm_arch_vcpu_ioctl_run+0x145/0x5c80 arch/x86/kvm/x86.c:7534
RSP: 0018:ffff88809603faf0 EFLAGS: 00010297
RAX: ffff88809b346140 RBX: ffff8880b3b4e000 RCX: ffff8880959e845c
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff8880959e8268
RBP: ffff88809603fc40 R08: ffff88809b346140 R09: 0000000000000001
R10: ffff88809603fc60 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8880959e8118 R14: 0000000000000000 R15: ffff8880959e8040
 kvm_vcpu_ioctl+0x3de/0xc50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2685
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x4469d9
RSP: 002b:00007f3a347f4308 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004cb438 RCX: 00000000004469d9
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 00000000004cb430 R08: 00007f3a347f4700 R09: 0000000000000000
R10: 00007f3a347f4700 R11: 0000000000000246 R12: 00000000004cb43c
R13: 000000000049b058 R14: 6d766b2f7665642f R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..