Now, it's the first time I encountered a kernel panic on a system that I can only access remotely (i.e. not physical access). The kernel panic I encountered is basically the one described here, only that the kernel version was:
Pid: 15483, comm: kvm Not tainted 2.6.32-30-server #59-Ubuntu MS-7522
The system is an Ubuntu 10.04 and I've been using ksplice in order to keep it secure without reboots.
The whole panic obviously resulted effectively in an unresponsive system. Since it runs VMs, this is not acceptable. Now, my question is this: is there a way to configure the system (e.g. via sysctl.conf) to reboot automatically when it encounters a kernel panic? If there is such an option, but it is not recommended to use it, please provide pointers or information as to why it is not recommended so I can male a well-informed decision whether to use it or refrain from using it.
For your reference, below the excerpt from syslog:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffffa0339e6a>] gfn_to_rmap+0x2a/0x80 [kvm]
PGD 182eff067 PUD 2103cd067 PMD 0
Oops: 0000 [#1] SMP
last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
CPU 2
Modules linked in: btrfs zlib_deflate crc32c libcrc32c ufs qnx4 hfsplus hfs minix ntfs vfat msdos fat jfs xfs exportfs reiserfs ksplice_a2zjpxfc ksplice_aeduoyr1 ksplice_ocpqubki ksplice_koav9q4r_vmlinux_new ksplice_koav9q4r ksplice_6rzac0n3_vmlinux_new ksplice_6rzac0n3 ksplice_sqv65gpe ksplice_74bgebjk ksplice_l13a9izo_vmlinux_new ksplice_l13a9izo ksplice_51l2thd5_vmlinux_new ksplice_51l2thd5 ksplice_mzqhwd6a ksplice_0k98nifa_vmlinux_new ksplice_0k98nifa ksplice_c0g8d8te_vmlinux_new ksplice_c0g8d8te ksplice_6jvv7tl8_vmlinux_new ksplice_6jvv7tl8 ksplice_o2xegqal ksplice_r7xdx1no ksplice_ly8vh9y3_vmlinux_new ksplice_ly8vh9y3 nls_cp437 ip6table_filter ip6_tables kvm_intel kvm bridge stp nls_utf8 cifs ipt_LOG ipt_MASQUERADE ipt_REJECT xt_recent xt_state xt_tcpudp iptable_filter iptable_nat nf_nat nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 xt_multiport ip_tables x_tables fbcon tileblit font bitblit softcursor snd_hda_intel vga16fb vgastate snd_hda_codec snd_hwdep nouveau snd_pcm ttm snd_timer snd drm_kms_helper soundcore snd_page_alloc drm lp i2c_algo_bit parport multipath linear aacraid 3w_9xxx 3w_xxxx raid10 raid456 async_pq async_xor xor async_memcpy async_raid6_recov raid6_pq async_tx raid1 raid0 ahci r8169 mii sata_nv sata_sil sata_via [last unloaded: ksplice_a2zjpxfc_ocfs2_new]
Pid: 15483, comm: kvm Not tainted 2.6.32-30-server #59-Ubuntu MS-7522
RIP: 0010:[<ffffffffa0339e6a>] [<ffffffffa0339e6a>] gfn_to_rmap+0x2a/0x80 [kvm]
RSP: 0018:ffff88014ee4d828 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 400000000001ec15 RCX: ffff8801d5e28990
RDX: 0000000000000023 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88014ee4d838 R08: 0000000000000023 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000007 R12: 0000000000000001
R13: 00000000000ba08a R14: ffff880032c0dbb0 R15: ffff88014ee4d928
FS: 00007f1b0d201700(0000) GS:ffff880008e40000(0000) knlGS:0000000000000000
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000158378000 CR4: 00000000000026f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kvm (pid: 15483, threadinfo ffff88014ee4c000, task ffff88000d274500)
Stack:
ffff8800b418d0a8 ffff8801d5e28000 ffff88014ee4d868 ffffffffa0339f5f
<0> ffff8801d5e28000 ffffc90016afa8a8 fff0000000000fff 000000018849a000
<0> ffff88014ee4d8b8 ffffffffa033a4cf 0000000000000001 ffff8800b418d0a8
Call Trace:
[<ffffffffa0339f5f>] rmap_remove+0x9f/0x1c0 [kvm]
[<ffffffffa033a4cf>] kvm_set_pte_rmapp+0xff/0x170 [kvm]
[<ffffffffa033653d>] kvm_handle_hva+0x9d/0x120 [kvm]
[<ffffffffa033a3d0>] ? kvm_set_pte_rmapp+0x0/0x170 [kvm]
[<ffffffffa0336601>] kvm_set_spte_hva+0x21/0x30 [kvm]
[<ffffffff8155e2ce>] ? _spin_lock+0xe/0x20
[<ffffffffa0322aa4>] kvm_mmu_notifier_change_pte+0x44/0x60 [kvm]
[<ffffffff81130e3e>] __mmu_notifier_change_pte+0x3e/0x90
[<ffffffff811172a4>] do_wp_page+0x674/0x850
[<ffffffff81095228>] ? tick_dev_program_event+0x68/0xd0
[<ffffffff8108a059>] ? __hrtimer_start_range_ns+0x189/0x400
[<ffffffff81117c2c>] handle_mm_fault+0x2ec/0x3c0
[<ffffffff81113846>] ? follow_page+0x2d6/0x350
[<ffffffff81117e39>] __get_user_pages+0x139/0x480
[<ffffffffa033de1e>] ? T.1169+0x1fe/0x2e0 [kvm]
[<ffffffff81118219>] get_user_pages+0x49/0x50
[<ffffffff81045b27>] get_user_pages_fast+0x157/0x1c0
[<ffffffffa0323af1>] gfn_to_pfn+0x41/0x150 [kvm]
[<ffffffffa034026d>] tdp_page_fault+0x9d/0x140 [kvm]
[<ffffffff81195177>] ? mb_cache_entry_insert+0xb7/0x1d0
[<ffffffffa033cc2f>] kvm_mmu_page_fault+0x1f/0xa0 [kvm]
[<ffffffffa037dbf8>] handle_ept_violation+0x68/0x130 [kvm_intel]
[<ffffffffa0380a8a>] vmx_handle_exit+0xca/0x250 [kvm_intel]
[<ffffffffa032f997>] vcpu_enter_guest+0x227/0x4c0 [kvm]
[<ffffffffa032fcac>] __vcpu_run+0x7c/0x350 [kvm]
[<ffffffffa033621d>] kvm_arch_vcpu_ioctl_run+0x8d/0x1d0 [kvm]
[<ffffffffa03252e3>] kvm_vcpu_ioctl+0x473/0x5c0 [kvm]
[<ffffffff811567b2>] vfs_ioctl+0x22/0xa0
[<ffffffff81084fa6>] ? common_timer_set+0x116/0x1a0
[<ffffffff81156951>] do_vfs_ioctl+0x81/0x410
[<ffffffff81156d61>] sys_ioctl+0x81/0xa0
[<ffffffff810131b2>] system_call_fastpath+0x16/0x1b
Code: 00 55 48 89 e5 48 83 ec 10 48 89 1c 24 4c 89 64 24 08 0f 1f 44 00 00 41 89 d4 48 89 f3 e8 3f 9b fe ff 41 83 fc 01 48 89 c6 75 19 <48> 2b 18 48 c1 e3 03 48 03 58 18 48 89 d8 4c 8b 64 24 08 48 8b
RIP [<ffffffffa0339e6a>] gfn_to_rmap+0x2a/0x80 [kvm]
RSP <ffff88014ee4d828>
CR2: 0000000000000000
---[ end trace 18481f74af4eef67 ]---
The kernel parameter that you're looking for is
kernel.panic=1(where 1 is the number of seconds before rebooting).You can add that to your sysctl.conf, sysctl.d, boot line, or however you normally set your kernel parameters. Make sure you have some way of monitoring your uptime so that you know when kernel panics have occurred.