Proxmox on HyperV, start VM crash if more than 2815MB of memory

[gogito]

My Hardware:
Ryzen 7 7800X3D
96GB DDR5
4TB NVME
Onboard 2.5G Lan
X520-DA2 2x10G SFP+
The machine been running stable and I can use VMs with VMware and HyperV with 32GB of ram just fine. Although I can't seem to enable Nested Virtualization with VMware).

Windows 11 25H2
HyperV enabled
Nested Virtualization enabled
Proxmox 9.1 with kernel 6.17 installed in a HyperV VM with 8 cores, 16GB of memory and 128G of storage configured with ZFS.

I try a VM configured with Q35, OVMF for UEFI and 4 CPU.

If I configure the VM with 2815MB Memory or below, it will start and work fine.

But if I set it to be above that, it will instantly crash on start with this in the Proxmox journalctl: KVM: entry failed, hardware error 0xffffffff.

Does anyone has any experience with this? Seems like a QEMU issue?

Another thread with the same issue with Incus VM on QEMU:
https://discuss.linuxcontainers.org...ry-limit-greater-than-2815mib-is-set/24941/13

 

[UdoB]

You did not tell us much about your hardware. But this line:

When I start a VM with more than 2815MB of ram

calls for: have you run memtest86+? If not: run it over night, at least several hours. At least two or three full "cycles".

How much RAM does the system have? Can you start a Linux machine with that amount of Ram? (And use that RAM inside of the VM?) Does the same VM succesfully run on another node? (If you have one.) Is it a new VM or an old one? Does a fresh - installed purely for testing - VM with that OS run successfully?

There are so many details you could test... many more than I can mention here ;-)

----
Sidenote, off-topic:

Another thread with the same issue:

It gives me "Powered by Discourse, best viewed with JavaScript enabled" - so no, not available for me. (Yes, you may beat me for this one...)

 

[gogito]

You did not tell us much about your hardware. But this line:

calls for: have you run memtest86+? If not: run it over night, at least several hours. At least two or three full "cycles".

How much RAM does the system have? Can you start a Linux machine with that amount of Ram? (And use that RAM inside of the VM?) Does the same VM succesfully run on another node? (If you have one.) Is it a new VM or an old one? Does a fresh - installed purely for testing - VM with that OS run successfully?

There are so many details you could test... many more than I can mention here ;-)

----
Sidenote, off-topic:

It gives me "Powered by Discourse, best viewed with JavaScript enabled" - so no, not available for me. (Yes, you may beat me for this one...)

Hi, sorry for the lack of information in the post, I updated with more information

 

[gogito]

Anyone has any idea?

 

[beisser]

so incus is affected as well per the other thread. this would suggest to me a hyper-v specific issue, not a proxmox issue as proxmox and incus are two entirely different products which just happen to be based on linux. other people there mention other failing qemu-solutions when running on hyper-v.

you can open as suggested an issue upstream with qemu and see if they are interested in finding out why qemu behaves this way while running on linux on hyper-v on AMD-hardware (intel works as per that thread).

i personally cant see too many people running proxmox on hyper-v though (or nested at all) except for experimental setups to try something out.
reason is that nested virtualization tends to perform rather badly (im running nutanix ce on proxmox and performance is rather meh).

 

[gogito]

so incus is affected as well per the other thread. this would suggest to me a hyper-v specific issue, not a proxmox issue as proxmox and incus are two entirely different products which just happen to be based on linux. other people there mention other failing qemu-solutions when running on hyper-v.

you can open as suggested an issue upstream with qemu and see if they are interested in finding out why qemu behaves this way while running on linux on hyper-v on AMD-hardware (intel works as per that thread).

i personally cant see too many people running proxmox on hyper-v though (or nested at all) except for experimental setups to try something out.
reason is that nested virtualization tends to perform rather badly (im running nutanix ce on proxmox and performance is rather meh).

That's true, though per the incus thread it seems OpenSuse QEMU works so it seems like it's fixable per QEMU side. I'll file an issue.

About performance, since I haven't been able to actually get it working to my liking, I'm currently just migrating some VMs directly to HyperV. I'm not gonna run nested for use, it's more of a backup when I need to maintenance the main server and to run stuff where performance is not a priority.