FYI, we noticed the following commit (built with gcc-6):

commit: b00b798255eb414246718eeec93d1ef10f894445 ("x86/fixmap: Add LDT entries to user-shared fixmap")
https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git WIP.x86/pti

in testcase: boot

on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -m 512M

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


+------------------------------------------+------------+------------+
|                                          | 23be87b4dd | b00b798255 |
+------------------------------------------+------------+------------+
| boot_successes                           | 8          | 0          |
| boot_failures                            | 2          | 12         |
| BUG:kernel_hang_in_test_stage            | 2          |            |
| BUG:unable_to_handle_kernel              | 0          | 12         |
| Oops:#[##]                               | 0          | 12         |
| RIP:acpi_find_root_pointer               | 0          | 12         |
| Kernel_panic-not_syncing:Fatal_exception | 0          | 12         |
+------------------------------------------+------------+------------+



[    0.000000] BUG: unable to handle kernel paging request at ffffffff8700040e
[    0.000000] IP: acpi_find_root_pointer+0x3e/0x146
[    0.000000] PGD 2012067 P4D 2012067 PUD 2013063 PMD 0 
[    0.000000] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.14.0-00117-gb00b798 #2
[    0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[    0.000000] task: ffffffff82016500 task.stack: ffffffff82000000
[    0.000000] RIP: 0010:acpi_find_root_pointer+0x3e/0x146
[    0.000000] RSP: 0000:ffffffff82003e60 EFLAGS: 00010082
[    0.000000] RAX: ffffffff8700040e RBX: ffff88001ffcf1b2 RCX: 0000000000000000
[    0.000000] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff822e6358
[    0.000000] RBP: ffffffff82003e88 R08: ffffffff8261ee40 R09: 0000000000000000
[    0.000000] R10: ffffffff835c6021 R11: 0000000000000001 R12: 000000001ffd0000
[    0.000000] R13: 000000000238d000 R14: ffffffff82003f28 R15: 0000000000000000
[    0.000000] FS:  0000000000000000(0000) GS:ffffffff82369000(0000) knlGS:0000000000000000
[    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.000000] CR2: ffffffff8700040e CR3: 0000000002011000 CR4: 00000000000406b0
[    0.000000] Call Trace:
[    0.000000]  ? acpi_os_get_root_pointer+0x16/0x1c
[    0.000000]  ? acpi_initialize_tables+0x42/0x55
[    0.000000]  ? acpi_table_init+0x52/0x1d2
[    0.000000]  ? acpi_boot_table_init+0x1f/0x68
[    0.000000]  ? setup_arch+0x82a/0x8df
[    0.000000]  ? cpumask_check+0x41/0x48
[    0.000000]  ? start_kernel+0x5f/0x557
[    0.000000]  ? secondary_startup_64+0xa5/0xb0
[    0.000000] Code: bf 0e 04 00 00 e8 59 0b 10 ff 48 85 c0 75 1c 41 b8 02 00 00 00 b9 0e 04 00 00 48 c7 c2 c5 be ef 81 be a2 00 00 00 e9 9e 00 00 00 <0f> b7 18 48 89 c7 be 02 00 00 00 e8 32 0b 10 ff c1 e3 04 81 fb 
[    0.000000] RIP: acpi_find_root_pointer+0x3e/0x146 RSP: ffffffff82003e60
[    0.000000] CR2: ffffffff8700040e
[    0.000000] ---[ end trace 2507864299958132 ]---


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