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[Question] Does LinuxKernelDirect boot mode support VMBus synthetic NIC, or only GCS protocol? #2600

@akr2dev

Description

@akr2dev

I'm building a Linux VM using the Host Compute Service (HCS) LinuxKernelDirect boot mode on Windows 11 25H2. The VM boots and runs fine with SCSI storage , but I cannot get networking to function and hv_netvsc loads but never probes a device.

What I've done (host side, all confirmed working)

  1. Created HCN endpoint via HcnCreateEndpoint → gets IP, MAC, switch port
  2. Created HCN namespace via HcnCreateNamespace (Type: HostDefault)
  3. Bound endpoint to namespace via HcnModifyNamespace
  4. Get-HnsGuestNetworkService shows the VM's GNS in State 3 (running)
  5. Get-HnsEndpoint shows the endpoint with VirtualMachine field set to the VM's GUID
  6. hnsdiag list all confirms endpoint is attached to the switch

Comparison with WSL2

I compared HNS state between WSL2 (which has working networking) and my VM:

WSL2 My VM
GuestNetworkService State 3 State 3
Endpoint State 2 2
VirtualMachine field Set Set
Switch port attached Yes Yes
eth0 in guest Works Missing

The HNS/HCN state is identical, yet WSL2 gets a network interface and my VM doesn't.

So I want to confirm if HcsCreateComputeSystem with LinuxKernelDirect create a VMBus synthetic NIC channel, or does it rely exclusively on the GCS protocol for guest networking?

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