[libvirt-users] Kernel panic after kernel update

HI! 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? (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 unknown-block(0,0) [ 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: 0xffffffff80000000-0xffffffffbfffffff)