Host crash when running nested VM

[GLucas]

Hello!

I've got an issue, whenever I try to run a nested VM, I get the Guru meditation error

In this case my host is Win10, with a Ubuntu 22.04 VM nesting a Win7

I'm using VirtualBox on my host and KVM on my Ubuntu.

i'll link you my VBox.log and hope you can find why it happens.

Thanks a lot !

[scottgus1]

The posted log is incomplete and does not show a Guru Meditation. Was it possibly copied while the error window was still open? If so, the log will be complete when all windows for the VM including error windows are closed.

This appears to be the first level of nesting, based on the real PC DMI info:

00:00:04.744707 DMI Product Name: ZenBook UX425EA_UX425EA
00:00:04.748913 DMI Product Version: 1.0

The VM looks good as a by-itself VM, but not too well provisioned as a nesting VM:

00:00:04.949571 NumCPUs <integer> = 0x0000000000000002 (2)
00:00:04.949573 RamSize <integer> = 0x0000000100000000 (4 294 967 296, 4.0 GiB)
00:00:04.949770 VRamSize <integer> = 0x0000000001000000 (16 777 216, 16.0 MiB)

The host has 4 cores and 16GB RAM, 9.9GB available RAM at the logged run. More RAM may be OK in the first VM so the second VM can have some, but probably only one processor in the second VM. (You might be able to squeeze 3 processors in the first VM, so the second VM can have 2.)

The big moose on campus is a missing host CPU feature that is needed for decent nested VMs:

00:00:06.243678 VMX - Virtual-Machine Extensions = 1 (1)
00:00:06.243684 Ept - Extended Page Tables = 1 (1)
00:00:06.243686 UnrestrictedGuest - Unrestricted guest = 1 (1)
00:00:06.243688 VmcsShadowing - VMCS shadowing = 0 (0)

Without that, this nested VM project may be dead on arrival.

FWIW if the second level of VM is a Docker, that may not work as a nested VM.

[GLucas]

Thanks for the fast reponse!

It is possible that the VM wasnt closed when I copied the logs.
If it still doesnt work, i'll attach logs again after closing the VM.

Ok I will try to set 3 CPU cores for the host and see what happens.

Don't you think that my win7 could only need 1 core so I let the 2 left for Ubuntu?

00:00:06.243688 VmcsShadowing - VMCS shadowing = 0 (0)

I really dont know what's that, i'll have a look.

FWIW if the second level of VM is a Docker, that may not work as a nested VM.

There isnt any Docker involved in my Ubuntu

[scottgus1]

Don't you think that my win7 could only need 1 core so I let the 2 left for Ubuntu?

With that info, the 2-processor setup seems like it would be OK. Though 7 works on 1 processor it can do well on 2.

FWIW the log from the first level Virtualbox doesn't contain anything regarding the second level Virtualbox. So a log from both levels would present a more complete picture.

[GLucas]

Hello,

So I've tried what you told me to try and sadly, it didnt help. It stills crash when running the VM.

00:00:06.243688 VmcsShadowing - VMCS shadowing = 0 (0)

Do you think that not having VMCS Shadowing is the issue?
Or maybe it is a KVM issue ? I should try to use VBox instead of KVM?

It's not like my win7 is slow, stutters or anything, it just crashed even before starting to configure Windows.

I've check my log folder and I only have these files but I cannot upload them since they are too heavy, it looks the same as the first one that I uploaded but it's now much more voluminous. (EDIT: I've compressed it but it' still to voluminous... )

Thanks,

[mpack]

Logs fit if they are zipped. And if the VM crashes immediately on launch then the log shouldn't be very big - though sometimes it's because it contains a zillion repetitions of a single runaway event: if so you can trim those out and leave a note in the log to say so.

[scottgus1]

Do you think that not having VMCS Shadowing is the issue?

It will probably be an issue, but I'm not sure it is this problem's issue.

Or maybe it is a KVM issue ? I should try to use VBox instead of KVM?

Theoretically, according to the Virtualbox manual, KVM should be OK as the virtualizer inside the first VM. It would be good if you could try Virtualbox instead of KVM, just to see what happens.

One other thing regarding the logs: Your screenshot appears to show that your Windows host is hiding known extensions. That highlighted Vbox.log is actually Vbox.log.1, the second oldest log. The file "Vbox" with no showing extension is the newest Vbox.log. Web-search how to make your Windows show all extensions to avoid this confusion and security issue.

[fth0]

Do you think that not having VMCS Shadowing is the issue?

No, it should just bring a large performance impact.

[GLucas]

Logs fit if they are zipped. And if the VM crashes immediately on launch then the log shouldn't be very big - though sometimes it's because it contains a zillion repetitions of a single runaway event: if so you can trim those out and leave a note in the log to say so.

I've zipped it and it still too voluminous (148kb)

[scottgus1]

Occasionally that happens. You'll have to split the file in the middle and post two zips.

[GLucas]

Occasionally that happens. You'll have to split the file in the middle and post two zips.

Didnt think about that..
Thanks for the tip!

[GLucas]

Theoretically, according to the Virtualbox manual, KVM should be OK as the virtualizer inside the first VM. It would be good if you could try Virtualbox instead of KVM, just to see what happens.

I've tried it and it result with the same issue, it crashes right away..

[scottgus1]

Here's the Guru Meditation:

00:07:16.169834 !!R0-Assertion Failed!!
00:07:16.169835 Expression: <NULL>
00:07:16.169835 Location : D:\tinderbox\win-7.0\src\VBox\VMM\VMMAll\PGMAllPool.cpp(5128) void __cdecl pgmPoolTrackDeref(struct PGMPOOL *,struct PGMPOOLPAGE *)
00:07:16.169862 enmKind=34 GCPhys=00000000acd5b000
00:07:16.169868 Changing the VM state from 'RUNNING' to 'GURU_MEDITATION'
00:07:16.169881 Console: Machine state changed to 'Stuck'
00:07:16.170124 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
00:07:16.170125 !!
00:07:16.170125 !! VCPU2: Guru Meditation -2701 (VERR_VMM_RING0_ASSERTION)
00:07:16.170134 !!
00:07:16.170138 !!R0-Assertion Failed!!

Please take a look here for a similar situation, which unfortunately we never heard back on: viewtopic.php?t=103993

[mpack]

I've zipped it and it still too voluminous (148kb)

That's very strange. The limit for archive files (zip, rar, etc) is supposed to be 256KB. My own CloneVDI download is larger than 148KB. Perhaps this setting got lost when the phpBB version was recently upgraded. I'll query it with the admins.

[GLucas]

I've zipped it and it still too voluminous (148kb)

That's very strange. The limit for archive files (zip, rar, etc) is supposed to be 256KB. My own CloneVDI download is larger than 148KB. Perhaps this setting got lost when the phpBB version was recently upgraded. I'll query it with the admins.

Basically I had to split in half the log file as advised by Scottgus.
The limit for uploading file here is 128 KB