#1400 Double faults in Linux VMX non-root mode guest (<ENTRY_TRAMPOLINE>)

[reet]

Hi,

We have been using Bochs for many years now to assert the correct functioning of our VT-x hypervisor implementation [1]. Each new feature runs through integration where the hypervisor is deployed to different targets, Bochs is one of them. The test runs the hypervisor virtualizing two Linux guests in VMX non-root mode.

Since we upgraded our guest Linux kernel to 4.14, we are periodically seeing an error which does not happen on "real" hardware, see the attached files.

It seems that the fault is related to the Meltdown / Spectre mitigations which came in with the 4.14 Linux kernel. Do you have any idea what the problem could be? Please inform me if you need more information to track down the problem.

Kind regards

[1] - https://muen.sk

[reet]

It also happens with 4.18 kernel.

[Stanislav Shwartsman]

Unfortunately I am not an expert with kernel debug.
Minimum required information to look at it would be:

• How can we reproduce the issue ?
• Can you attach the kernel image (for both 4.14,4.18 and kernel which working well) and augment it with instructions to reproduce ?
• Can you add Bochs output ?
• Which CPU it was configured to run ? Did you try other models ? For example from AMD ?
• Which Bochs version was used ? Did you try latest SVN ?
  There is a way to screen out issues with Spectre and Meltdown mitigations by hacking CPUID/MSRs to make cpu 'not vulnarable' to Spectre and Meltdown. I could do that and check if it affects the kernel and makes it work well. But again I need to see the kernel and try it "online",

[Stanislav Shwartsman]

Got no response to several years and nobody else reported similar issue.
Rejected as 'cannot be reproduced'