Hi, In qemu version 2.6.0-rc3, qemu-system-x86_64 hangs for me for some CPU/machine combinations. Some affected combinations are SandyBridge (q35), Haswell (q35), Opteron_G4 (pc), IvyBridge (q35). Some working combinations are core2duo (pc), Nehalem (q35), phenom (pc), Opteron_G1 (q35).
On the broken combinations, there is no console output other than TCG warnings, such as warning: TCG doesn't support requested feature: CPUID.01H:EDX.vme [bit 1] Qemu command line is as follows. qemu-system-x86_64 \ -kernel arch/x86/boot/bzImage \ -M q35 -cpu SandyBridge -usb -usbdevice wacom-tablet \ -hda core-image-minimal-qemux86-64.ext3 -no-reboot -m 256 \ --append "root=/dev/sda rw mem=256M vga=0 uvesafb.mode_option=640x480-32 oprofile.timer=1 console=ttyS0 console= tty" \ -nographic -monitor none The problem seems to be kernel version independent; I have seen it with 3.2, mainline, and -next kernels. The kernel configuration as well as the root file system are available from https://github.com/groeck/linux-build-test/tree/master/rootfs/x86_64 Bisect points to commit 19dc85dba23c0 ("target-i386: Add XSAVE extension"). Bisect log is attached. Please let me know if there is anything I can do to help tracking down the problem. Thanks, Guenter --- Bisect log: # bad: [f419a626c76bcb26697883af702862e8623056f9] usb/uhci: move pid check # good: [a8c40fa2d667e585382080db36ac44e216b37a1c] Update version for v2.5.0 release git bisect start 'HEAD' 'v2.5.0' # bad: [253785e3b96f48c52568c312cec0a5ec596c527f] scripts/feature_to_c.sh: Include qemu/osdep.h rather than config.h git bisect bad 253785e3b96f48c52568c312cec0a5ec596c527f # good: [f4109dba216f2df61a6098fdd7a6f2d2be4ac848] scripts/kvm/kvm_stat: Moved DebugfsProvider git bisect good f4109dba216f2df61a6098fdd7a6f2d2be4ac848 # good: [8983b670f62ab5e5e8dd2690bf8304123651bfe5] block: qemu-iotests - add test for snapshot, commit, snapshot bug git bisect good 8983b670f62ab5e5e8dd2690bf8304123651bfe5 # good: [d7bea75d35a44023efc9d481d3a1a2600677b2ef] qapi: Avoid use of misnamed DO_UPCAST() git bisect good d7bea75d35a44023efc9d481d3a1a2600677b2ef # good: [c9f19dff101e2c2cf3fa3967eceec2833e845e40] Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging git bisect good c9f19dff101e2c2cf3fa3967eceec2833e845e40 # good: [fc1ec1acffd29d54c0c4266d30d38b2399d42f4f] Merge remote-tracking branch 'remotes/mjt/tags/pull-trivial-patches-2016-02-11' into staging git bisect good fc1ec1acffd29d54c0c4266d30d38b2399d42f4f # bad: [62b58ba58bfebdb8a1c447beaa1285cc21249d15] target-i386: Implement BNDMOV git bisect bad 62b58ba58bfebdb8a1c447beaa1285cc21249d15 # good: [1906b2af7c2345037d9b2fdf484b457b5acd09d1] target-i386: Rearrange processing of 0F 01 git bisect good 1906b2af7c2345037d9b2fdf484b457b5acd09d1 # bad: [f4f1110e4b34797ddfa87bb28f9518b9256778be] target-i386: Enable control registers for MPX git bisect bad f4f1110e4b34797ddfa87bb28f9518b9256778be # bad: [19dc85dba23c0db1ca932c62e453c37e00761628] target-i386: Add XSAVE extension git bisect bad 19dc85dba23c0db1ca932c62e453c37e00761628 # good: [121f3157887f92268a3d6169e2d4601f9292020b] target-i386: Rearrange processing of 0F AE git bisect good 121f3157887f92268a3d6169e2d4601f9292020b # first bad commit: [19dc85dba23c0db1ca932c62e453c37e00761628] target-i386: Add XSAVE extension