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.
BUG: unable to handle page fault for address: ffffffffffffffea
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD aa8f067 P4D aa8f067 PUD aa91067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 4154 Comm: syz-executor.0 Not tainted 5.17.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:arch_atomic_fetch_sub arch/x86/include/asm/atomic.h:190 [inline]
RIP: 0010:atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:177 [inline]
RIP: 0010:__refcount_sub_and_test include/linux/refcount.h:272 [inline]
RIP: 0010:__refcount_dec_and_test include/linux/refcount.h:315 [inline]
RIP: 0010:refcount_dec_and_test include/linux/refcount.h:333 [inline]
RIP: 0010:kref_put include/linux/kref.h:64 [inline]
RIP: 0010:eventfd_ctx_put+0x13/0x90 fs/eventfd.c:112
Code: e3 ff 48 8b 54 24 10 48 8b 44 24 08 e9 7d fd ff ff 66 0f 1f 44 00 00 55 be 04 00 00 00 48 89 fd e8 52 61 e3 ff b8 ff ff ff ff <f0> 0f c1 45 00 83 f8 01 74 06 85 c0 7e 51 5d c3 48 8d 7d 64 48 b8
RSP: 0018:ffffc900024cf778 EFLAGS: 00010246
RAX: 00000000ffffffff RBX: ffffc900024cfa30 RCX: ffffffff81c69dfe
RDX: fffffbfffffffffe RSI: 0000000000000004 RDI: ffffffffffffffea
RBP: ffffffffffffffea R08: 0000000000000001 R09: ffffffffffffffed
R10: fffffbfffffffffd R11: 0000000000000000 R12: 0000000000000020
R13: 00000000ffffffea R14: ffffffffffffffea R15: ffffc90002768000
FS:  00007f4cd6bb3700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffea CR3: 000000001d11a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 kvm_xen_eventfd_assign arch/x86/kvm/xen.c:1268 [inline]
 kvm_xen_setattr_evtchn arch/x86/kvm/xen.c:1327 [inline]
 kvm_xen_hvm_set_attr+0x5d4/0x1330 arch/x86/kvm/xen.c:403
 kvm_arch_vm_ioctl+0x5bf/0x12c0 arch/x86/kvm/x86.c:6505
 kvm_vm_ioctl+0xaf3/0x1f20 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4656
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __x64_sys_ioctl+0x11f/0x190 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f4cd743f5a9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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:00007f4cd6bb3168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4cd7560f80 RCX: 00007f4cd743f5a9
RDX: 00000000200005c0 RSI: 000000004048aec9 RDI: 0000000000000004
RBP: 00007f4cd749a580 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc489f65cf R14: 00007f4cd6bb3300 R15: 0000000000022000
 </TASK>
Modules linked in:
CR2: ffffffffffffffea
---[ end trace 0000000000000000 ]---
RIP: 0010:arch_atomic_fetch_sub arch/x86/include/asm/atomic.h:190 [inline]
RIP: 0010:atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:177 [inline]
RIP: 0010:__refcount_sub_and_test include/linux/refcount.h:272 [inline]
RIP: 0010:__refcount_dec_and_test include/linux/refcount.h:315 [inline]
RIP: 0010:refcount_dec_and_test include/linux/refcount.h:333 [inline]
RIP: 0010:kref_put include/linux/kref.h:64 [inline]
RIP: 0010:eventfd_ctx_put+0x13/0x90 fs/eventfd.c:112
Code: e3 ff 48 8b 54 24 10 48 8b 44 24 08 e9 7d fd ff ff 66 0f 1f 44 00 00 55 be 04 00 00 00 48 89 fd e8 52 61 e3 ff b8 ff ff ff ff <f0> 0f c1 45 00 83 f8 01 74 06 85 c0 7e 51 5d c3 48 8d 7d 64 48 b8
RSP: 0018:ffffc900024cf778 EFLAGS: 00010246
RAX: 00000000ffffffff RBX: ffffc900024cfa30 RCX: ffffffff81c69dfe
RDX: fffffbfffffffffe RSI: 0000000000000004 RDI: ffffffffffffffea
RBP: ffffffffffffffea R08: 0000000000000001 R09: ffffffffffffffed
R10: fffffbfffffffffd R11: 0000000000000000 R12: 0000000000000020
R13: 00000000ffffffea R14: ffffffffffffffea R15: ffffc90002768000
FS:  00007f4cd6bb3700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffea CR3: 000000001d11a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	e3 ff                	jrcxz  0x1
   2:	48 8b 54 24 10       	mov    0x10(%rsp),%rdx
   7:	48 8b 44 24 08       	mov    0x8(%rsp),%rax
   c:	e9 7d fd ff ff       	jmpq   0xfffffd8e
  11:	66 0f 1f 44 00 00    	nopw   0x0(%rax,%rax,1)
  17:	55                   	push   %rbp
  18:	be 04 00 00 00       	mov    $0x4,%esi
  1d:	48 89 fd             	mov    %rdi,%rbp
  20:	e8 52 61 e3 ff       	callq  0xffe36177
  25:	b8 ff ff ff ff       	mov    $0xffffffff,%eax
* 2a:	f0 0f c1 45 00       	lock xadd %eax,0x0(%rbp) <-- trapping instruction
  2f:	83 f8 01             	cmp    $0x1,%eax
  32:	74 06                	je     0x3a
  34:	85 c0                	test   %eax,%eax
  36:	7e 51                	jle    0x89
  38:	5d                   	pop    %rbp
  39:	c3                   	retq
  3a:	48 8d 7d 64          	lea    0x64(%rbp),%rdi
  3e:	48                   	rex.W
  3f:	b8                   	.byte 0xb8