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

commit: 68ad4275838d223a06a3211fb2f27c8b6f44cd24 ("x86/mm/cpa: Add sanity check for existing mappings")
https://github.com/0day-ci/linux UPDATE-20180916-004446/Thomas-Gleixner/x86-mm-cpa-Improve-large-page-preservation-handling/20180915-063911

in testcase: trinity
with following parameters:

	runtime: 300s

test-description: Trinity is a linux system call fuzz tester.
test-url: http://codemonkey.org.uk/projects/trinity/


on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -m 256M

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


+-------------------------------------------------------+------------+------------+
|                                                       | cc13b49187 | 68ad427583 |
+-------------------------------------------------------+------------+------------+
| boot_successes                                        | 10         | 0          |
| boot_failures                                         | 0          | 8          |
| WARNING:at_arch/x86/mm/pageattr.c:#__change_page_attr | 0          | 8          |
| EIP:__change_page_attr                                | 0          | 8          |
+-------------------------------------------------------+------------+------------+



[   12.633167] WARNING: CPU: 0 PID: 1 at arch/x86/mm/pageattr.c:830 __change_page_attr+0xd21/0x10f0
[   12.634536] Modules linked in:
[   12.634958] CPU: 0 PID: 1 Comm: swapper Tainted: G                T 4.19.0-rc2-00018-g68ad427 #1
[   12.636083] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   12.637166] EIP: __change_page_attr+0xd21/0x10f0
[   12.637778] Code: 8b 45 e4 8b 55 e8 89 c6 81 e6 00 f0 ff ff 81 e2 ff ff 0f 00 e9 31 ff ff ff b8 ff ff ff ff c7 45 dc 00 00 00 00 e9 6f fb ff ff <0f> 0b 8b 45 c0 80 48 24 02 e9 19 f4 ff ff 81 c4 e0 00 00 00 b8 f4
[   12.640184] EAX: 00000002 EBX: 00000000 ECX: 00000000 EDX: 00000002
[   12.641003] ESI: 00001800 EDI: 000001e3 EBP: cd1d7e94 ESP: cd1d7da8
[   12.641802] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010202
[   12.642677] CR0: 80050033 CR2: 08497008 CR3: 01d53000 CR4: 000406f0
[   12.643496] Call Trace:
[   12.643846]  ? find_held_lock+0x34/0xc0
[   12.644375]  __change_page_attr_set_clr+0x3c/0x180
[   12.645017]  ? mutex_unlock+0x10/0x20
[   12.645493]  ? vm_unmap_aliases+0x12d/0x1d0
[   12.646063]  ? vm_unmap_aliases+0x1b/0x1d0
[   12.646639]  ? _raw_spin_unlock+0x2c/0x50
[   12.647170]  change_page_attr_set_clr+0x131/0x3a0
[   12.647797]  set_memory_ro+0x44/0x50
[   12.648303]  set_pages_ro+0x1b/0x20
[   12.648769]  mark_rodata_ro+0x8a/0xf0
[   12.649266]  ? rest_init+0x1d0/0x1d0
[   12.649755]  kernel_init+0x31/0x110
[   12.650203]  ? schedule_tail_wrapper+0x9/0xc
[   12.650798]  ret_from_fork+0x2e/0x38
[   12.651273] irq event stamp: 2257432
[   12.651753] hardirqs last  enabled at (2257431): [<c10a7b55>] console_unlock+0x215/0x5d0
[   12.652819] hardirqs last disabled at (2257432): [<c100145b>] trace_hardirqs_off_thunk+0xc/0x10
[   12.653960] softirqs last  enabled at (2257428): [<c17634eb>] __do_softirq+0x38b/0x3c1
[   12.654958] softirqs last disabled at (2257395): [<c10148cc>] call_on_stack+0x4c/0x60
[   12.655965] ---[ end trace e0f028e4efa9dcc5 ]---


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,
lkp