Hi, I'm running lots of kvm instances for doing kernel boot tests. Unfortunately the test system itself is not stable enough, I got scary errors in both kvm and the host kernel. Like this. [294025.795382] kvm used greatest stack depth: 2896 bytes left [310388.622083] kvm[1864]: segfault at c ip 00007f498e9f6a81 sp 00007f4994b9fca0 error 4 in kvm[7f498e960000+33b000] [310692.050589] kvm[4332]: segfault at 10 ip 00007fca662620b9 sp 00007fca70472af0 error 6 in kvm[7fca661cc000+33b000] [312608.950120] kvm[18931]: segfault at 8 ip 00007f95962a10a5 sp 00007f959d777170 error 4 in kvm[7f959620b000+33b000] [312622.941640] kvm[19123]: segfault at 10 ip 00007f406f5580b9 sp 00007f4077d8b350 error 6 in kvm[7f406f4c2000+33b000] [313917.860951] kvm[28789]: segfault at c ip 00007f718f4dfa81 sp 00007f7198459520 error 4 in kvm[7f718f449000+33b000] [313919.177192] kvm used greatest stack depth: 2864 bytes left [314061.390945] kvm used greatest stack depth: 2208 bytes left [327479.676068] BUG: Bad page state in process kvm pfn:59ac9 [327479.676455] page:ffffea000166b240 count:0 mapcount:0 mapping: (null) index:0x7fd346bc6 [327479.677083] page flags: 0x100000000000014(referenced|dirty) [327479.677575] Modules linked in: [327479.677897] Pid: 11423, comm: kvm Not tainted 3.4.0 #131 [327479.678272] Call Trace: [327479.678538] [<ffffffff81107343>] bad_page+0xe6/0xfb [327479.678897] [<ffffffff811079c6>] get_page_from_freelist+0x534/0x6f6 [327479.679314] [<ffffffff81107d92>] __alloc_pages_nodemask+0x20a/0x75e [327479.679729] [<ffffffff8108e121>] ? finish_task_switch+0x4c/0xf6 [327479.680136] [<ffffffff81143477>] ? lookup_page_cgroup_used+0xe/0x24 [327479.680548] [<ffffffff811079b5>] ? get_page_from_freelist+0x523/0x6f6 [327479.680970] [<ffffffff811367c8>] alloc_pages_current+0xd2/0xf3 [327479.681369] [<ffffffff811012e4>] __page_cache_alloc+0xa1/0xae [327479.681761] [<ffffffff8110b144>] __do_page_cache_readahead+0x107/0x20b [327479.682188] [<ffffffff8110b0cc>] ? __do_page_cache_readahead+0x8f/0x20b [327479.682615] [<ffffffff811293b0>] ? anon_vma_prepare+0xb4/0x137 [327479.683010] [<ffffffff8110b521>] ra_submit+0x21/0x25 [327479.683375] [<ffffffff81102f7a>] filemap_fault+0x18a/0x383 [327479.683757] [<ffffffff8111d6b3>] __do_fault+0xc8/0x451 [327479.684128] [<ffffffff81120103>] handle_pte_fault+0x2de/0x844 [327479.684522] [<ffffffff8114446e>] ? mem_cgroup_count_vm_event+0x1a/0x96 [327479.684944] [<ffffffff811218ac>] handle_mm_fault+0x1a6/0x1bb [327479.685339] [<ffffffff819b8c12>] do_page_fault+0x405/0x42a [327479.685722] [<ffffffff8112619e>] ? do_mmap_pgoff+0x299/0x2f3 [327479.686115] [<ffffffff813fe03d>] ? trace_hardirqs_off_thunk+0x3a/0x3c [327479.686534] [<ffffffff819b5b45>] page_fault+0x25/0x30 [327479.686898] Disabling lock debugging due to kernel taint The same host kernel, in another test box: [770644.256817] kvm_get_msr_common: 2123 callbacks suppressed [770644.257475] kvm: 31889: cpu0 unhandled rdmsr: 0x2 [770644.258103] kvm: 31889: cpu0 unhandled rdmsr: 0x3 [770644.258707] kvm: 31889: cpu0 unhandled rdmsr: 0x4 [770644.259322] kvm: 31889: cpu0 unhandled rdmsr: 0x5 [770644.259914] kvm: 31889: cpu0 unhandled rdmsr: 0x6 [770644.260499] kvm: 31889: cpu0 unhandled rdmsr: 0x7 [770644.261108] kvm: 31889: cpu0 unhandled rdmsr: 0x8 [770644.261700] kvm: 31889: cpu0 unhandled rdmsr: 0x9 [770644.262302] kvm: 31889: cpu0 unhandled rdmsr: 0xa [770644.262883] kvm: 31889: cpu0 unhandled rdmsr: 0xb [909290.636655] kvm[31619]: segfault at 40 ip 00007fcb3d8c4254 sp 00007fcb41bcaec0 error 4 in kvm[7fcb3d82e000+33b000] Please drop me hints if I can help debugging it (a week later, after returning from LinuxCon Japan), thank you. Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>