port-arm/58194: aarch64: the vmt(4) driver does not attach to anything

[pho%cielonegro.org@localhost]

>Number:         58194
>Category:       port-arm
>Synopsis:       aarch64: the vmt(4) driver does not attach to anything
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Apr 25 12:15:01 +0000 2024
>Originator:     PHO
>Release:        10.0
>Organization:
TNF
>Environment:
NetBSD yukari.cielonegro.org 10.0 NetBSD 10.0 (GENERIC64) #0: Thu Mar 28 08:33:33 UTC 2024  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/evbarm/compile/GENERIC64 evbarm
>Description:
On NetBSD/aarch64 running as a VMware guest, the vmt(4) driver is supposed to attach to fdt:

> vmt*            at fdt?                 # VMware Tools

but the driver in fact doesn't attach to anything.
>How-To-Repeat:
Boot NetBSD/aarch64 10.0 on VMware.
>Fix:
On this architecture vmt(4) used to search for a node "/hypervisor" in the FDT and probed the VMware hypervisor call only when the node was found. However, things appear to have changed and VMware no longer provides the FDT node.
    
Since vmt(4) doesn't actually need to read anything from FDT, and the hypervisor call logically resides in virtual CPUs themselves, it would be better to attach it directly to cpu, just like how it's probed on x86.

I have a working patch and I'm going to post it later.