Hi list, I'm trying to debug a strange issue I have, and I'd appreciate some help. I've upgraded libvirt to 1.2.2, on Scientific Linux, with qemu-kvm-0.12.1.2-2.415.el6_5.3 Here’s my analysis so far: I figured out that libvirt uses HMP to get the list of models from qemu-kvm by running qemu-kvm -cpu ?model -nodefconfig. This returns the following: x86 Opteron_G5 AMD Opteron 63xx class CPU x86 Opteron_G4 AMD Opteron 62xx class CPU x86 Opteron_G3 AMD Opteron 23xx (Gen 3 Class Opteron) x86 Opteron_G2 AMD Opteron 22xx (Gen 2 Class Opteron) x86 Opteron_G1 AMD Opteron 240 (Gen 1 Class Opteron) x86 Haswell Intel Core Processor (Haswell) x86 SandyBridge Intel Xeon E312xx (Sandy Bridge) x86 Westmere Westmere E56xx/L56xx/X56xx (Nehalem-C) x86 Nehalem Intel Core i7 9xx (Nehalem Class Core i7) x86 Penryn Intel Core 2 Duo P9xxx (Penryn Class Core 2) x86 Conroe Intel Celeron_4x0 (Conroe/Merom Class Core 2) x86 cpu64-rhel5 QEMU Virtual CPU version (cpu64-rhel5) x86 cpu64-rhel6 QEMU Virtual CPU version (cpu64-rhel6) x86 n270 Intel(R) Atom(TM) CPU N270 @ 1.60GHz x86 athlon QEMU Virtual CPU version 0.12.1 x86 pentium3 x86 pentium2 x86 pentium x86 486 x86 coreduo Genuine Intel(R) CPU T2600 @ 2.16GHz x86 qemu32 QEMU Virtual CPU version 0.12.1 x86 kvm64 Common KVM processor x86 core2duo Intel(R) Core(TM)2 Duo CPU T7700 @ 2.40GHz x86 phenom AMD Phenom(tm) 9550 Quad-Core Processor x86 qemu64 QEMU Virtual CPU version 0.12.1 The comment describing the function parsing this list states that the output is expected to be as follows: /* Format: * <arch> <model> * qemu-0.13 encloses some model names in []: * <arch> [<model>] */ static int virQEMUCapsParseX86Models(const char *output, virQEMUCapsPtr qemuCaps) { but this function doesn’t strip the rest of the line, so the models array becomes: Breakpoint 1, x86Decode (cpu=0x7fffd82a8460, data=0x7fffd8272d00, models=0x7fffd82b7440, nmodels=25, preferred=0x7fffd82a81f0 "Nehalem", flags=0) at cpu/cpu_x86.c:1487 1487 { (gdb) p models $1 = (const char **) 0x7fffd82b7440 (gdb) p *models $2 = 0x7fffd82ba240 "Opteron_G5 AMD Opteron 63xx class CPU", ' ' <repeats 22 times> (gdb) p *models@25 $3 = {0x7fffd82ba240 "Opteron_G5 AMD Opteron 63xx class CPU", ' ' <repeats 22 times>, 0x7fffd82c8c30 "Opteron_G4 AMD Opteron 62xx class CPU", ' ' <repeats 22 times>, 0x7fffd8169e00 "Opteron_G3 AMD Opteron 23xx (Gen 3 Class Opteron) ", 0x7fffd8169cb0 "Opteron_G2 AMD Opteron 22xx (Gen 2 Class Opteron) ", 0x7fffd8169b60 "Opteron_G1 AMD Opteron 240 (Gen 1 Class Opteron)", ' ' <repeats 11 times>, 0x7fffd8169a10 "Haswell Intel Core Processor (Haswell)", ' ' <repeats 18 times>, 0x7fffd81697e0 "SandyBridge Intel Xeon E312xx (Sandy Bridge)", ' ' <repeats 16 times>, 0x7fffd8169690 "Westmere Westmere E56xx/L56xx/X56xx (Nehalem-C) ", 0x7fffd8169460 "Nehalem Intel Core i7 9xx (Nehalem Class Core i7) ", 0x7fffd81693f0 "Penryn Intel Core 2 Duo P9xxx (Penryn Class Core 2) ", 0x7fffd8169310 "Conroe Intel Celeron_4x0 (Conroe/Merom Class Core 2) ", 0x7fffd8169230 "cpu64-rhel5 QEMU Virtual CPU version (cpu64-rhel5) ", 0x7fffd8169150 "cpu64-rhel6 QEMU Virtual CPU version (cpu64-rhel6) ", 0x7fffd82ba2b0 "n270 Intel(R) Atom(TM) CPU N270 @ 1.60GHz ", 0x7fffd81690e0 "athlon QEMU Virtual CPU version 0.12.1", ' ' <repeats 17 times>, 0x7fffd8169000 "pentium3", ' ' <repeats 50 times>, 0x7fffd8168f90 "pentium2", ' ' <repeats 50 times>, 0x7fffd8168eb0 "pentium", ' ' <repeats 50 times>, 0x7fffd82a8760 "486", ' ' <repeats 50 times>, 0x7fffd8168e40 "coreduo Genuine Intel(R) CPU", ' ' <repeats 11 times>, "T2600 @ 2.16GHz ", 0x7fffd8168d60 "qemu32 QEMU Virtual CPU version 0.12.1", ' ' <repeats 17 times>, 0x7fffd82bb150 "kvm64 Common KVM processor", ' ' <repeats 28 times>, 0x7fffd8168cf0 "core2duo Intel(R) Core(TM)2 Duo CPU T7700 @ 2.40GHz ", 0x7fffd8168c10 "phenom AMD Phenom(tm) 9550 Quad-Core Processor ", 0x7fffd8168b30 "qemu64 QEMU Virtual CPU version 0.12.1", ' ' <repeats 17 times>} cpuModellsAllowed then does a strcmp between “Nehalem” and "Nehalem Intel Core i7 9xx (Nehalem Class Core i7)” which fails, and the vm fails to start with: 2014-03-10 14:56:16.917+0000: 8328: info : qemuDomainDefineXML:6231 : Creating domain '530df8bd-7b64-4553-b4f4-18922e1327bf' 2014-03-10 14:56:17.114+0000: 8329: warning : x86Decode:1515 : Preferred CPU model Nehalem not allowed by hypervisor; closest supported model will be used 2014-03-10 14:56:17.114+0000: 8329: error : x86Decode:1571 : internal error: Cannot find suitable CPU model for given data Kind regards, Ruben Kerkhof