How to create Virtual Machine that uses 5-level paging (LA57)?

Jan Ringoš 0

Hey everyone,

Does anyone know, if it's possible, and if so how, to get a Windows Server Virtual Machine running NTKRLA57.exe kernel? That is: 57-bit address space (5-level paging) instead of classic 48-bit (4-level)?

https://en.wikipedia.org/wiki/Intel_5-level_paging

I can't get my hands on a physical Ice Lake+ or 8004/9004+ yet, so I was hoping to do some testing and validation on HW in Azure. I'm able to create VMs running on Xeons that should support this feature, but yet, the VMs run only regular 4-level paging.

I was assured virtualization doesn't degrade the paging mode, and that Windows Server will use 5-level paging kernel automatically in the presence of LA57 bit in CPUID. Perhaps that wasn't accurate.

I was advised to try bcdedit.exe /set linearaddress57 optin command to force the 57-bit kernel, but that only renders the VM unbootable ...which I kinda expected.

Thanks in advance for any ideas and thought.

Prrudram-MSFT 26,196 Reputation points

2024-11-20T13:56:47.0466667+00:00

Hi @Jan Ringoš
I am reviewing this query, please standby while I get back.
deherman-MSFT 37,586 Reputation points Microsoft Employee

2024-11-20T21:01:17.4966667+00:00

@Jan Ringoš I don't see any information about running 5-level paging on virtual machines. Can you share the source for that information?
Jan Ringoš 0 Reputation points

2024-11-21T13:55:11.1466667+00:00

@deherman-MSFT It's a question. I haven't found anything on this, neither stating to the contrary (that it'd not be supported), so I'm asking if it's possible and how. Since the CPUs used and the OSs imaged both do support 5-level paging, I assumed it would be possible.
deherman-MSFT 37,586 Reputation points Microsoft Employee

2024-11-21T17:07:51.86+00:00

@Jan Ringoš Thanks for clarifying. Checking internally to see if we have any information about this.

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