FYI, we noticed the following commit (built with gcc-7):

commit: 8bb2610bc4967f19672444a7b0407367f1540028 ("x86/entry/64/compat: Preserve r8-r11 in int $0x80")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

in testcase: kernel_selftests
with following parameters:

	group: kselftests-03

test-description: The kernel contains a set of "self tests" under the tools/testing/selftests/ directory. These are intended to be small unit tests to exercise individual code paths in the kernel.
test-url: https://www.kernel.org/doc/Documentation/kselftest.txt


on test machine: qemu-system-x86_64 -enable-kvm -cpu host -smp 2 -m 4G

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


selftests: test_syscall_vdso_32
========================================
[RUN]	Executing 6-argument 32-bit syscall via VDSO
[WARN]	Flags before=0000000000200ed7 id 0 00 o d i s z 0 a 0 p 1 c
[WARN]	Flags  after=0000000000200606 id 0 00 d i 0 0 p 1 
[WARN]	Flags change=00000000000008d1 0 00 o s z 0 a 0 0 c
[OK]	Arguments are preserved across syscall
[NOTE]	R11 has changed:0000000000200606 - assuming clobbered by SYSRET insn
[OK]	R8..R15 did not leak kernel data
[RUN]	Executing 6-argument 32-bit syscall via INT 80
[OK]	Arguments are preserved across syscall
[FAIL]	R8 has changed:0000000000000000
[FAIL]	R9 has changed:0000000000000000
[FAIL]	R10 has changed:0000000000000000
[FAIL]	R11 has changed:0000000000000000
[RUN]	Executing 6-argument 32-bit syscall via VDSO
[WARN]	Flags before=0000000000200ed7 id 0 00 o d i s z 0 a 0 p 1 c
[WARN]	Flags  after=0000000000200606 id 0 00 d i 0 0 p 1 
[WARN]	Flags change=00000000000008d1 0 00 o s z 0 a 0 0 c
[OK]	Arguments are preserved across syscall
[NOTE]	R11 has changed:0000000000200606 - assuming clobbered by SYSRET insn
[OK]	R8..R15 did not leak kernel data
[RUN]	Executing 6-argument 32-bit syscall via INT 80
[OK]	Arguments are preserved across syscall
[FAIL]	R8 has changed:0000000000000000
[FAIL]	R9 has changed:0000000000000000
[FAIL]	R10 has changed:0000000000000000
[FAIL]	R11 has changed:0000000000000000
[RUN]	Running tests under ptrace
not ok 1..14 selftests:  test_syscall_vdso_32 [FAIL]


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