Hi, as described in the subject already, our hardware-node suddenly freezes after starting a HVM domU and restarts itself without proper shutdown. We''ve set "noreboot" as kernel parameter, but the system keeps getting unresponsable after starting a HVM domU (PV domUs are no problem). Here are the hardware specs: ProLiant DL385 G7 96G RAM 2x AMD Opteron Processor 6272 (16-core) We have cloned the entire system (Debian 6.0.3) from one of our other hardware-nodes with less resources, where we don''t have this issue. Following versions are currently installed: linux-image-2.6.32-5-xen-amd64 2.6.32-39 xen-hypervisor-4.0-amd64 4.0.1-4 Unfortunately, we don''t any kind of logfile, as the box restarts right after starting a domU. We currently have 4 of the new boxes, where we can reproduce the described behaviour. Any idea how to debug this? Here''s a comparison of /proc/cpu: this is an old node: vendor_id : AuthenticAMD cpu family : 16 model : 9 model name : AMD Opteron(tm) Processor 6128 stepping : 1 cpu MHz : 2989655.870 cache size : 512 KB fpu : yes fpu_exception : yes cpuid level : 5 wp : yes flags : fpu de tsc msr pae mce cx8 apic mtrr mca cmov pat clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow constant_tsc rep_good nonstop_tsc extd_apicid amd_dcm pni cx16 popcnt hypervisor lahf_lm cmp_legacy extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch nodeid_msr bogomips : 4000.20 TLB size : 1024 4K pages clflush size : 64 cache_alignment : 64 address sizes : 48 bits physical, 48 bits virtual power management: ts ttp tm stc 100mhzsteps hwpstate this is the new node: vendor_id : AuthenticAMD cpu family : 21 model : 1 model name : AMD Opteron(TM) Processor 6272 stepping : 2 cpu MHz : 1048360.785 cache size : 2048 KB fpu : yes fpu_exception : yes cpuid level : 13 wp : yes flags : fpu de tsc msr pae mce cx8 apic mtrr mca cmov pat clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm constant_tsc nonstop_tsc extd_apicid amd_dcm pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 popcnt aes avx hypervisor lahf_lm cmp_legacy extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch xop nodeid_msr arat bogomips : 4200.14 TLB size : 1536 4K pages clflush size : 64 cache_alignment : 64 address sizes : 48 bits physical, 48 bits virtual power management: ts ttp tm 100mhzsteps hwpstate [9] thanks Sascha