qemu-system-sparc stays "parked"?

Not sure where to put this, so "netbsd-users@" seems like a good starting
point.

I usually build packages for sparc natively, but only during cold-weather
months when the electric bills are lower and the added heat from the
machines is welcome.

With NetBSD-11 nearing release, I wanted to set up building with a
'qemu-system-sparc' guest since my build host is always on and has plenty
of RAM and processor capacity.  (I tried the pkgsrc cross-building setup
once, but it screwed up my host packages in the process.)

The host is NetBSD/amd64-10.1_STABLE w/12GB RAM and a quad-core processor.
The disk image for the guest is qcow2.  I tried installing with "-machine
SS-20", but it would hang during the "running MAKEDEV" stage.  Installing
as the default SS-5 had no problem.  I would then shut the guest down
and restart it with "-machine SS-20 -cpu TI-SuperSparc-61 -m 2048" (I
wanted to use "-smp 4", but anything other than uniprocessor would hang
after "waiting 2 seconds for SCSI busses to settle".

So, single-processor SS-20 with max RAM it is.  I eventually worked out
how to get NFS working (export host-resident filesystems to 127/8 w/
"-noresvport -noresvmnt" and add those flags on the file server to
exports to the host machine).  I am using "-nic user,..." if that has
some bearing on the issue.

When I set about to build the first package, the guest went down about
3 levels of dependency and just sat there.  'top' on the host shows it
in "parked" state, occasionally moving from one CPU to another.  Pressing
ctrl-T in the guest elicits the expected output, but it never (seems to)
progress.

Any suggestions about what's going on?

Anyone else using 'qemu-system-foo' to build packages for your RAM or
CPU-limited "foo" systems?  With pkgsrc tree on NFS?  Tips?  Tricks?
Techniques?

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