kern/54611: NVMM faults on a Windows 95 install

[rnestor%mac.com@localhost]

>Number:         54611
>Category:       kern
>Synopsis:       NVMM faults on a Windows 95 install
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Oct 09 17:20:00 +0000 2019
>Originator:     Bob Nestor
>Release:        NetBSD-9.0 BETA Oct-8, qem-nvmm 3.1
>Organization:
>Environment:
NetBSD bandit.home.net 9.0_BETA NetBSD 9.0_BETA (GENERIC) #0: Sun Oct  6 11:20:50 UTC 2019  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

QEMU emulator version 3.1.0
Copyright (c) 2003-2018 Fabrice Bellard and the QEMU Project developers
>Description:
Windows-95C installation from an official CD fails with the following:

NetBSD Virtual Machine Monitor accelerator is operational
qemu-system-x86_64: NVMM: Mem Assist Failed [gpa=0xb8040]
qemu-system-x86_64: NVMM: Failed to execute a VCPU.


The same install works under XEN using the same QEMU parameters as follows:
qemu-img create -f raw /home/Win95C.dsk 2G
qemu-system-x86_64 -accel nvmm -cpu pentium -smp 1 \
 -cdrom /home/Win95C.iso -name "Windows-95 Install" \
 -netdev tap,id=nd0,ifname=tap0,script=no,downscript=no \
 -device rtl8139,netdev=nd0 \
 -drive file=/home/Win95C.dsk,media=disk,format=raw

Attempts to find a magic set of parameters to QEMU have so far all produced the same results.
>How-To-Repeat:
As described above.
>Fix:
Unknown.