[libvirt-users] Kernel panic after kernel update

Martin Kletzander mkletzan at redhat.com
Wed Dec 7 10:45:09 UTC 2016

On Tue, Dec 06, 2016 at 11:22:17AM +0100, Michael Ströder wrote:
>On one qemu-kvm instance a kernel update failed and booting the image is not
>possible anymore (see below). A dozen other VMs are correctly working after the
>upgrade. Anything I can quickly try to make it work again?

What do you mean by "update failed"?  Was the update cancelled in the
middle, so that there may be newer kernel set up, but modules missing or
something?  If the machine was just killed in the middle of writing, the
disk data might be corrupted and it depends on your configuration
whether you just need to check the journal or just re-install it (in
case there is no way to know what parts are corrupted).  Try booting the
older kernel (or newer one), or boot a rescue CD and fix the
installation if possible.

In any case, this is not related to qemu, and even more unrelated to

>(This is not really a bad emergency case because I could simply re-install and
>re-configure with ansible. But I'd like to learn about these cases...)
>Ciao, Michael.
>Loading Linux 4.8.12-1-default ...
>[    0.651328] Kernel panic - not syncing: VFS: Unable to mount root fs on
>[    0.654408] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.12-1-default #1
>[    0.656941] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
>[    0.661166]  0000000000000000 ffffffff813a4252 ffff9a5348c4d000 ffff9a5349957e60
>[    0.664652]  ffffffff8118e3fa ffff9a5300000010 ffff9a5349957e70 ffff9a5349957e08
>[    0.668124]  ffffffff8118e715 ffff9a5349957e78 0000000000000001 0000000000000000
>[    0.671457] Call Trace:
>[    0.672460]  [<ffffffff8102eefe>] dump_trace+0x5e/0x310
>[    0.674389]  [<ffffffff8102f2cb>] show_stack_log_lvl+0x11b/0x1a0
>[    0.676570]  [<ffffffff81030001>] show_stack+0x21/0x40
>[    0.678480]  [<ffffffff813a4252>] dump_stack+0x5c/0x7a
>[    0.680369]  [<ffffffff8118e3fa>] panic+0xd5/0x217
>[    0.682169]  [<ffffffff81f56419>] mount_block_root+0x1fe/0x2c0
>[    0.684285]  [<ffffffff81f56668>] prepare_namespace+0x12b/0x161
>[    0.686439]  [<ffffffff81f56103>] kernel_init_freeable+0x1f6/0x20a
>[    0.688675]  [<ffffffff816c727a>] kernel_init+0xa/0x100
>[    0.690623]  [<ffffffff816d485f>] ret_from_fork+0x1f/0x40
>[    0.696659] DWARF2 unwinder stuck at ret_from_fork+0x1f/0x40
>[    0.698858]
>[    0.699533] Leftover inexact backtrace:
>[    0.699533]
>[    0.701580]  [<ffffffff816c7270>] ? rest_init+0x90/0x90
>[    0.703944] Kernel Offset: 0x0 from 0xffffffff81000000 (relocation range:

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