VINF_EM_TRIPLE_FAULT (Linux 32 & 64 guest on CentOS 7 host)

[PKU]

This worked up until I updated CentOS 7 yesterday, which broke VirtualBox 4.2, so I upgraded that to 5.1.22 r115126 (Qt5.6.1). Log and desktop video is attached.

This guest VM has no OS installed. It tries booting via PXE and quickly fails. The file it receives from the PXE server is a CLI Linux 32 bit very thin menu app (pxelinux.0). It appears to crash either while downloading this or immediately after downloading it.

I have tried various permutations of CPU options for the guest VM (HW Virtualization, Extended features, etc.) as well as defining the VM as Ubuntu 32 or 64 bit. Nothing helps.

[PKU]

Guest VM log file

[PKU]

Guest .vbox file

[Frank Mehnert]

Certainly a VirtualBox bug, actually a duplicate of other tickets like #16758. You can workaround the problem by enabling VT-x for this VM.

[PKU]

No, VT-x, PAE/NX, etc. don't have any effect. Having read the prior bugs I tried the workarounds with no joy. :(

Desktop video is too big to upload here. I've uploaded it to Google Drive. Link is [here]​https://drive.google.com/drive/folders/0B3e9qdhCsKRPY1VCYk9KZk1XMjg?usp=sharing

[PKU]

With VT-x turned on per comment.

[PKU]

With VT-x turned on per comment.

[PKU]

Desktop video for 64 bit Ubuntu VM client with VT-x enabled is [here]​https://drive.google.com/open?id=0B3e9qdhCsKRPdGxRWEVDSV9HSW8. I have also uploaded .vbox and log files for this version. It crashes exactly the same way (apparantly) as the 32 bit version with no VT-x, PAE/NX, etc.

Please let me know if there is any specific configuration you want me to try.

Thanks for the help with this!

[Frank Mehnert]

Well, then we need to be able to reproduce the problem. Is the PXE binary public available?

[PKU]

Binary sent to thin clients during PXE boot

[PKU]

Binary uploaded.

[PKU]

I just tried this on another Linux host machine running Linux Mint 18.1, VirtualBox Version 5.0.40_Ubuntu r115130. It's broken in the same way in that version as well.

[michaln]

This is almost certainly a pxelinux bug, see ​https://bugzilla.syslinux.org/show_bug.cgi?id=54 . The bug was fixed over 2 years ago.

The bug is somewhat random and depending on the exact configuration and PXE implementation, it may do nothing bad or crash the system.

You may be able to work around it by downloading the VirtualBox Extension Pack and using the provided Intel PXE implementation; it's just different enough that it probably won't crash. But really you should update pxelinux.

[PKU]

THANK YOU! I downloaded the latest pxelinux.0 and now it gets further along (see screen shot). It doesn't run the PXE menu that's supposed to come up, but clearly this solved a big issue. It does seem odd that it worked under VirtualBox 4.2 but not 5.x.

I'll dig in and see what's broken regarding the menu not running, probably some obscure dependency hell in the new pxelinux.0 <sigh>

[PKU]

New stopping point using new pxelinux.0

[PKU]

It's now working using syslinux-6.04-pre1. I had to upgrade 2 files: pxelinux.0 ldlinux.c32

Thanks again!

[Frank Mehnert]

First reported in #13048. Closing as duplicate.