semantic: 0.194 other: 0.142 device: 0.082 files: 0.078 graphic: 0.074 permissions: 0.072 debug: 0.063 PID: 0.053 network: 0.046 performance: 0.046 vnc: 0.045 socket: 0.042 boot: 0.040 KVM: 0.024 debug: 0.458 files: 0.106 network: 0.077 other: 0.066 boot: 0.060 PID: 0.053 socket: 0.040 device: 0.028 vnc: 0.027 semantic: 0.024 performance: 0.020 graphic: 0.015 KVM: 0.014 permissions: 0.013 source tarball has errors when untarring If you download qemu-2.10.0.tar.xv and/or qemu-2.10.1.tar.xv, and follow the directions at https://www.qemu.org/download/, you get a tar error. To repro: $ wget https://download.qemu.org/qemu-2.10.0.tar.xz $ tar xJf qemu-2.10.0.tar.xz tar: qemu-2.10.0/roms/u-boot/scripts/Kconfig: Cannot open: File exists tar: Exiting with failure status due to previous errors $ tar --version tar (GNU tar) 1.29 Copyright (C) 2015 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later . This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Written by John Gilmore and Jay Fenlason. Apologies if I'm being an idiot here. I look in my crystal ball and deduce that you're doing this on a filesystem which isn't case-sensitive. This is bug #1714750, and it's really an issue with the u-boot code that we ship a copy of. You can work around it by extracting the sources with "tar xf qemu-2.10.0.tar.xz --exclude qemu-2.10.0/roms/u-boot/scripts/Kconfig" (the file that is excluded isn't needed to build QEMU). It looks like we never finished the fix for 1714750 -- it's fixed in upstream u-boot but we need to move forward to using that u-boot rather than the one we currently ship. Your crystal ball is correct! I was untarring in a Linux vbox, and was blindly assuming since it was on linux it was case sensitive. However, it was on a vboxsf shared with OSX, and apple's file system is case insensitive. Thanks so much for the rapid and nice response.