performance: 0.880 files: 0.878 device: 0.837 semantic: 0.820 other: 0.801 network: 0.791 graphic: 0.776 PID: 0.744 permissions: 0.700 debug: 0.660 socket: 0.651 boot: 0.625 vnc: 0.580 KVM: 0.491 qemu linux-user doesn't support OFD fcntl locks "Open file description locks (non-POSIX)", as they are described in fcntl(2) man page, aren't supported by qemu-user and attempting to use those results in EINVAL. I'm on Gentoo with latest QEMU version currently available (5.0.0-r2), and trying to emulate ppc64 and s390x on x86_64. Looking at linux-user/syscall.c, I'm guessing the issue is in (at least) `target_to_host_fcntl_cmd` where switch reaches the default clause as there're no cases for F_OFD_SETLK / F_OFD_SETLKW / F_OFD_GETLK. The attached patch fixes the issue for me. New patch version: fix target_to_host_fcntl_cmd mapping, avoid do_fcntl code duplication. Please check qemu-5.1.0. This has been fixed by: 2d92c6827ca0 ("linux-user: implement OFD locks") https://git.qemu.org/?p=qemu.git;a=commitdiff;h=2d92c6827ca0 perhaps you can send a patch to the qemu-devel ML to add the strace part. Thanks, the changes in 5.1.0 seem to work indeed. > perhaps you can send a patch to the qemu-devel ML to add the strace part Done.