FYI, we noticed the following commit (built with gcc-4.9):

commit: ab1bcc442070315bd0ce963331d5bb93d5c5476e ("x86/vdso: Move out the CPU number store")
url: https://github.com/0day-ci/linux/commits/Chang-S-Bae/x86-fsgsbase-64-Introduce-FS-GS-base-helper-functions/20180605-095329


in testcase: boot

on test machine: qemu-system-i386 -enable-kvm -cpu Haswell,+smep,+smap -m 360M

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+-------------------------------+------------+------------+
|                               | 053d1414b3 | ab1bcc4420 |
+-------------------------------+------------+------------+
| boot_successes                | 8          | 0          |
| boot_failures                 | 0          | 8          |
| BUG:kernel_hang_in_boot_stage | 0          | 8          |
+-------------------------------+------------+------------+



[    0.000000] clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[    0.000000] setup_percpu: NR_CPUS:8 nr_cpumask_bits:8 nr_cpu_ids:1 nr_node_ids:1
[    0.000000] percpu: Embedded 342 pages/cpu @(ptrval) s1371088 r0 d29744 u1400832
[    0.000000] pcpu-alloc: s1371088 r0 d29744 u1400832 alloc=342*4096
[    0.000000] pcpu-alloc: [0] 0 
BUG: kernel hang in boot stage
Linux version 4.17.0-rc3-00290-gab1bcc4 #1
Command line: ip=::::vm-vp-quantal-i386-50::dhcp root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-vp-quantal-i386-50/boot-1-quantal-core-i386.cgz-ab1bcc442070315bd0ce963331d5bb93d5c5476e-20180610-7731-3wa87x-0.yaml ARCH=i386 kconfig=i386-randconfig-h1-06101053 branch=linux-devel/devel-catchup-201806101444 commit=ab1bcc442070315bd0ce963331d5bb93d5c5476e BOOT_IMAGE=/pkg/linux/i386-randconfig-h1-06101053/gcc-4.9/ab1bcc442070315bd0ce963331d5bb93d5c5476e/vmlinuz-4.17.0-rc3-00290-gab1bcc4 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-vp-quantal-i386/quantal-core-i386.cgz/i386-randconfig-h1-06101053/gcc-4.9/ab1bcc442070315bd0ce963331d5bb93d5c5476e/0 LKP_SERVER=inn debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 net.ifnames=0 printk.devkmsg=on panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 drbd.minor_count=8 systemd.log_level=err ignore_loglevel console=tty0 earlyprintk=ttyS0,115200 console=ttyS0,115200 vga=normal rw drbd.minor_count=8 rcuperf.shutdown=0

Elapsed time: 560



To reproduce:

        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email



Thanks,
Xiaolong