KVM: kernel panic when booting slackware installation media

Fabio_ppo · 10-20-2015, 09:59 AM

Greetings,

I'm trying to install slackware 14.1 guest on a host with the same OS and I'm having a problem that the guest crashes when I boot into the installation media.

Boot command:

Code:

	user@host:~/qemu$ qemu-kvm -monitor stdio -m 2064 -localtime -cdrom slackware64-14.1-install-dvd.iso -hda test_slack.qcow -boot d -net nic -net user -enable-kvm -cpu host

This all I could see from the kernel panic message, I wasn't able to scroll up using shift+page_up keys:

Code:

DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Stack:
ffffffff821247fe ffff880080471ed8 ffffffff8212483b 0000000000000000
ffff88000009b000 ffff880080471ed8 ffffffff821247fe 0000000000000000
0000000000000000 0000000000000000 0000000000000000 ffff880080471f08
Call Trace:
[<ffffffff821247fe>] ? check_bugs+0x2d/0x2d
[<ffffffff8212483b>] init_hw_perf_events+0X3d/0x51e
[<ffffffff821247fe>] ? check_bugs+0x2d/0x2d
[<ffffffff810002d2>] do_one_initcal1+0x102/0x160
[<ffffffff8211deea>] kerne1_init_freeable+0xb6/0x1df
[<ffffffff81b4d9f0>] ? rest_init+0x80/0x80
[<ffffffff81b4d9f0>] ? rest_init+0x80/0x80
[<ffffffff81b4d9fe>] kernel_init+0xe/0x180
[<ffffffff81b6f6dc>] ret_from_fork+0x7c/0Xb0
[<ffffffff81b4d9f0>] ? rest_init+0x80/0x80
Code: 82 fd ff 44 89 0d 99 82 fd ff 89 0d 4b 83 fd ff 7e 2b 83 e2 1f b8 03 00 00
00 b9 45 03 00 00 83 fa 02 0f 4f c2 89 05 60 82 fd ff <Of> 32 48 C1 e2 20 89 c0
48 09 c2 48 89 15 f6 82 fd ff e8 09 18
RIP [<ffffffff821257b0>] inte1_pmu_init+0x2d9/0x7a7
RSP <ffff880080471e80>
---[ end trace 4fb0a4e6d8ce3d05 ]---
Kernel panic - not syncing: Attempted to kill init! exitcode:0x0000000b

The problem seems to be triggered by "-cpu host" arguemnt. When I remove it the machine installs and runs fine. However, I need this arguemnt in order to tune the performance and utilize all CPU capabilities. This shows the different between the host/guest when removing the arguemnt:

Code:

user@host:~/qemu$ cat /proc/cpuinfo | grep flags | uniq
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm 
constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc 
aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 
cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave 
avx f16c rdrand lahf_lm ida arat epb xsaveopt pln pts dtherm tpr_shadow vnmi 
flexpriority ept vpid fsgsbase smep erms

Code:

user@guest:~$ cat /proc/cpuinfo | grep flags | uniq
flags           : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pse36 clflush mmx fxsr sse sse2 syscall nx lm rep_good nopl pni cx16 x2apic
 popcnt hypervisor lahf_lm

Side question:
What advantages of using TightVNC/TigerVNC over using the qemu viewer? I prefer a viewer with a scrutinized source code, dynamic screen resolution and good quality when viewing HD videos.

dyasny · 10-20-2015, 10:56 AM

First of all, not ALL the CPU features are supported by KVM, so if you have specific flags you need in the guest, add them to the command line explicitly.

Second, no VNC viewer will support playing HD videos, and will not provide sound passthrough anyway. You need to either use spice or SDL

Fabio_ppo · 10-20-2015, 11:36 AM

Thank you for clarification. I understand that the argument "-cpu host" works only if the flags are supported by the kvm, and that it is not possible to get audio from guest VMs. It seems that VBox is more usable from this aspect. This is interesting because I have seen some good kvm graphics performance on youtube, one of them was playing games on a guest vm with audio. Perhaps it was heavily customized which is something I'm trying to avoid.

Should I just research each flag then specify it if it's applicable, or there is a better way on how to optimize the performance of the VMs?

dyasny · 10-20-2015, 04:32 PM

Quote:

Originally Posted by Fabio_ppo

Thank you for clarification. I understand that the argument "-cpu host" works only if the flags are supported by the kvm, and that it is not possible to get audio from guest VMs.

Two not quite valid points, which are also unrelated.

1. Not absolutely all CPU features are supported by absolutely all versions of KVM, you likely are using some mismatching set of hardware/software. If you want a setup to work out of the box, why not use a proper virtualization management library, like libvirt, which will scan the host, and start guests with proper CPU flags set.

2. I didn't say sound wasn't supported, I said VNC display didn't support sound, there is a huge difference. I also said that other console types, like Spice or SDL did support sound and decent at least 2D kind of graphics.

Quote:

It seems that VBox is more usable from this aspect. This is interesting because I have seen some good kvm graphics performance on youtube, one of them was playing games on a guest vm with audio. Perhaps it was heavily customized which is something I'm trying to avoid.

vbox is a desktop oriented solution, KVM is a pure hypervisor, enterprise oriented. vbox is probably easier for a newbie to run and use on a single desktop, but it's absolutely useless when you;re running hundreds of servers with thousands of VMs. And again, if you simply run libvirt with virt-manager, life will be so much easier with KVM, you will forget about vbox

Quote:

Should I just research each flag then specify it if it's applicable, or there is a better way on how to optimize the performance of the VMs?

No, you simply use libvirt.