Proxmox crashes when I start 2 VMs with a single PCI pass-through

[ronzino]

In PVE 8.3.0 I have setup a Win11 VM with vGPU.
It works perfectly, windows see the gpu, install the official driver and it is able to use acceleration.
I also have an ethernet card, and i have tried to PCI pass-through it. It works like a charm (speed test, file transfer driver and so on perfect)

So in my opinion SR-IOV and IOMMU should be ok, as i can pass and virtualize GPU to a windows 11 VM.

Now i have removed the ethernet card pass-through from windows, as I would try to pass it to another VM.


This VM is a TrueNAS-Scale, that I am trying to install (never installed, fresh VM).
The TrueNAS VM boots and installation process starts IF

1. Windows VM is stopped and TrueNAS is running with ethernet pass-through
2. Windows VM is running and TrueNAS is running without ethernet pass-through

Whenever ethernet pass-through is enabled on TrueNAS and BOTH (windows and Truenas) VM star , PROXMOX crashes

It seems that even if (and of course) only one VM (TrueNAS) receive a device sharing, and VM try to run, the whole system crashes. I say this because I have also tried to not share the ethernet PCI device , but assign a vGPU id1 to win11 and vGPU id2 to TrueNAS... Host crashes as well.

What I am doing in the wrong way ?

 

[ronzino]

This seems to fix

Z

[SOLVED] Thread 'PCI passthrough causes Proxmox host to crash'

Dec 6, 2022

Hello,
I was trying to install an OPNsense VM on a host with Proxmox.
I installed it fine and then went to configure it and everything was still working.

I noticed that after I added a PCI device (NIC) as passthrough the host started crashing as soon as the VM was booting which means that if you enable it to start up on boot this would restart the host every ~2 minutes.

• Zx4ACQQ7
• crash crash reboot crashing opnsense vm passthrough passthrough nic
• Replies: 12
• Forum: Proxmox VE: Installation and configuration

It seems a problem with proxmox ballooning and pci-e pass-through .... it seems a sort of hidden requirements

16 GB ram on proxmox host

• vm1 min4Gb max8Gb
• vm2 min6gb max8Gb

without pci pass-through on vm2, everything works, two VMs can run together on the Host.
Instead as soon as I enable a pci pass-through on any VM and two VMs run together, Proxmox crash.

Changing ballooning settings to

16 GB ram on proxmox host

• vm1 min4Gb max6Gb
• vm2 min4gb max6Gb

IT WORKS (for now)

It seems (confirm) that PCI pass-through requires that there is no over memory allocation. I would like to better understand this to know the exact rule that rules this

 

[leesteken]

It seems a problem with proxmox ballooning and pci-e pass-through .... it seems a sort of hidden requirements

PCI(e) devices that are passed through can do Direct Memory Access (DMA) at any time. Therefore all VM memory must be pinned into actual host RAM. Memory over-commit does not work very well on Proxmox (which also requires 2GB at least).