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[6.4.0-rc9f] Windows 10 VM boot loop

Featured Replies

Noticed the Windows 10 VM could not reboot properly and was constantly going to the diagnostics screen in a boot loop. Using rather customised config that could be the issue, although I am focusing on low latency DPC for real-time audio/video/3d workloads, hopefully, with internal Windows timer below 0.5ms. It would be great if we can estimate the best VM performance configuration for Windows 10 on the Ryzen platform and have it in future iterations of unRAID.

 

unRAID kernel options: append isolcpus=8-15 nohz_full=8-15 rcu_nocbs=8-15 initrd=/bzroot

 

Attaching VM XML and diagnostics.

 

win10kvm.xml

 

Edited by realies

  • Author

Further testing and it seems the XML config has nothing to do with the issue. Any other option other than safe mode from the automatic repair window results in a restart, excluding the "no automatic reboot on error" type of option, which makes the machine hang. Windows works absolutely fine when booting from the same drive barebones. What would be an appropriate way of detecting where it fails? Selecting "Boot log" within msconfig->Boot does not produce any logs.

Edited by realies

Hi realies,

 

If you remove the extra parameters (isolcpus is ok) from your syslinux config, does that change the behavior with the VM at all?

 

- Jon

Did you install windows from the getgo with those kernel options enabled? 

has windows ever booted? or are the bootloops after a windows update? 

anything meaningful in the system event logs in the windows VM when you boot into safe mode?

  • Author

Assumed virtualisation could be inherited, although it turned out that enabling the Hyper-V components within Windows 10 and rebooting causes this particular issue with boot looping. Unfortunately, I have found that creating a system restore point before enabling the components does not help with returning to a working state and boot logging does not work at all. Nothing meaningful in the windows VM event logs.

23 hours ago, realies said:

Assumed virtualisation could be inherited, although it turned out that enabling the Hyper-V components within Windows 10 and rebooting causes this particular issue with boot looping. Unfortunately, I have found that creating a system restore point before enabling the components does not help with returning to a working state and boot logging does not work at all. Nothing meaningful in the windows VM event logs.

 

Question regarding the bolded statement.  Are you stating that in the VM configuration (XML) that if you enable Hyper-V, this causes boot looping, or are you talking about enabling something from within the Windows 10 VM itself?  I have not been able to recreate this issue on our own test systems.

  • Author

I mean exactly what is stated, enabling Hyper-V within Windows (from add/remove features) and rebooting causes the machine to go into a boot loop that does not go past the TianoCore screen. After three cycles, the Windows 10 recovery options menu is loaded up from which only the safe mode options are able to boot the VM. Have tried switching between versions of i440fx and Q35 without any difference. Bare metal booting from the same problematic setup has no issues at all. Perhaps this is a KVM/QEMU issue?

Edited by realies

Why are you enabling Hyper-V inside Windows 10?  Are trying to utilize nested virtualization?

Also, can you confirm this issue doesn't appear on 6.3.5?

  • Author

Indeed I have assumed that nested virtualisation can be utilised. Would it be possible to transfer 6.4.0-rc9f configuration to 6.3.5 without anything breaking, including the current trial period?

see here: https://ladipro.wordpress.com/2017/02/24/running-hyperv-in-kvm-guest/

 

Nested virtualization inside a KVM VM requires an additional kernel parameter, which by default isnt enabled in unraid. the following command would return 'Y' if it was enabled.

cat /sys/module/kvm_intel/parameters/nested

It also requires a fairly recent linux kernel\qemu\kvm version (which rc9 has), but im not sure 6.3.5 ticks all the boxes for it to work?

 

i've not tried nested virtualization so i cant vouch for if this will even work if you enabled the parameter, or what performance would be like in the nested VMs. 
I'm not sure what the use case is though when you can spin up VMs inside unraid anyway? 

 

Edited by billington.mark
words

  • Author

It seems nested visualisation is enabled in rc9f.

# cat /sys/module/kvm_amd/parameters/nested 
1

may have found the issue. remember you mentioning you were on ryzen....

 

Hyper-V on KVM does not work on AMD CPUs Fixed in kernel 4.12 for 1 vCPU
405a353a0e

 

and in kernel 4.13 for >1 vCPU
4aebd0e9ca
ab2f4d73eb
9b61174793
a12713c25b
1a5e185294

RHBZ 1440025

 

rc9f is using kernel 4.12.14. You should be able to boot if you drop down to 1 vCPU on the VM. 
Assuming the next RC has a bump to 4.13, your issue should hopefully be resolved.

 

Mark

may have found the issue. remember you mentioning you were on ryzen....

 
Hyper-V on KVM does not work on AMD CPUs Fixed in kernel 4.12 for 1 vCPU
405a353a0e

 

and in kernel 4.13 for >1 vCPU
4aebd0e9ca
ab2f4d73eb
9b61174793
a12713c25b
1a5e185294

RHBZ 1440025
 
rc9f is using kernel 4.12.14. You should be able to boot if you drop down to 1 vCPU on the VM. 
Assuming the next RC has a bump to 4.13, your issue should hopefully be resolved.
 
Mark
Thanks Mark!!!

Sent from my SM-G930P using Tapatalk

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