FYI, we noticed the following commit:

commit: cdfac8129693572ef91b9e7022d6ae07f1c8cc38 ("x86/asm: Rewrite sync_core() to use IRET-to-self")
https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/boot

in testcase: boot

on test machine: qemu-system-i386 -enable-kvm -smp 2 -m 256M

caused below changes:


+---------------------------------------------+------------+------------+
|                                             | 535a025bb9 | cdfac81296 |
+---------------------------------------------+------------+------------+
| boot_successes                              | 6          | 0          |
| boot_failures                               | 0          | 4          |
| kernel_BUG_at_arch/x86/kernel/alternative.c | 0          | 4          |
| invalid_opcode:#[##]SMP                     | 0          | 4          |
| EIP_is_at_apply_alternatives                | 0          | 4          |
| Kernel_panic-not_syncing:Fatal_exception    | 0          | 4          |
+---------------------------------------------+------------+------------+



[    0.429066] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.447516] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.455310] ------------[ cut here ]------------
[    0.459612] kernel BUG at arch/x86/kernel/alternative.c:386!
[    0.465842] invalid opcode: 0000 [#1] SMP
[    0.469305] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.0-rc7-00027-gcdfac81 #1
[    0.476137] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[    0.483617] task: c84cb040 task.stack: c84c4000
[    0.486773] EIP: 0060:[<c88a7068>] EFLAGS: 00210246 CPU: 0
[    0.490857] EIP is at apply_alternatives+0xa5/0x7e3
[    0.494426] EAX: d83b0ff0 EBX: c84abb75 ECX: 00000000 EDX: 000000ae
[    0.499509] ESI: 00000004 EDI: c84c5eb6 EBP: c84c5fbc ESP: c84c5e90
[    0.503883]  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
[    0.508031] CR0: 80050033 CR2: ffffffff CR3: 089df000 CR4: 00000690
[    0.512150] Stack:
[    0.514412]  c69f2b7c 00000003 00000004 fffffbfb 0ff0ae0f 00000089 c84abb81 d83b6984
[    0.529825]  e58900e8 cf49340f c84c5eec 00000002 c888dba0 c84c5f74 c84c5ed4 c683cc1e
[    0.537271]  c84c5f00 c84c5f14 c683d4f7 c84c5f00 0000002b c84c5f60 00000143 03c0003f
[    0.545924] Call Trace:
[    0.548885]  [<c69f2b7c>] ? __kmem_cache_create+0x37d/0x5c7
[    0.552895]  [<c683cc1e>] ? __cpuid+0x1a/0x2e
[    0.556362]  [<c683d4f7>] ? cpuid4_cache_lookup_regs+0x4ad/0x52f


To reproduce:

        git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script  # job-script is attached in this email



Thanks,
Kernel Test Robot