Avi, I'm getting the following panic very early on boot on a F16 VM (latest qemu.git head 40897c9):
[ 0.068018] Kernel panic - not syncing: Boot APIC ID in local APIC unexpected (-1 vs 0) [ 0.070006] Pid: 1, comm: swapper Not tainted 3.1.0-7.fc16.x86_64 #1 [ 0.071004] Call Trace: [ 0.072035] [<ffffffff814acb8e>] panic+0x91/0x1a5 [ 0.073027] [<ffffffff81b831ca>] native_smp_prepare_cpus+0x24c/0x300 [ 0.075010] [<ffffffff81b76c0d>] kernel_init+0x85/0x158 [ 0.075993] [<ffffffff810527eb>] ? schedule_tail+0x27/0x6c [ 0.076017] [<ffffffff814be5f4>] kernel_thread_helper+0x4/0x10 [ 0.077022] [<ffffffff81b76b88>] ? start_kernel+0x3b6/0x3b6 [ 0.078009] [<ffffffff814be5f0>] ? gs_change+0x13/0x13 After some debugging and I found out that this only happens when '-cpu host' is passed, and according to git bisect it's caused by the following commit: commit 66e3dd9282141b5ae75637c9676002cf3ceeb988 Author: Avi Kivity <a...@redhat.com> Date: Wed Nov 9 15:44:36 2011 +0200 i386: derive '-cpu host' from KVM_GET_SUPPORTED_CPUID Not sure if this is important, but here's procinfo information about one of my host's cpus: processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 23 model name : Intel(R) Core(TM)2 Duo CPU T9600 @ 2.80GHz stepping : 6 cpu MHz : 2801.000 cache size : 6144 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 2 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm tpr_shadow vnmi flexpriority bogomips : 5585.87 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: