Re: port-amd64/59887 (nvmm: running startx on an i386 guest kills the vm)

[riastradh%NetBSD.org@localhost]

Synopsis: nvmm: running startx on an i386 guest kills the vm

State-Changed-From-To: open->feedback
State-Changed-By: riastradh%NetBSD.org@localhost
State-Changed-When: Sun, 04 Jan 2026 14:33:35 +0000
State-Changed-Why:
1. Exactly what version of qemu are you using?

   pkg_info -I qemu

2. When did this start happening?

3. Does it happen if you use `-machine pc,accel=nvmm' instead of
   `-machine q35,accel=nvmm'?

4. Does it happen if you use `-machine pc,smm=on,accel=nvmm'?

The guest physical address here, 0xa0000, is exactly the start of the
VGA resource MMIO range (https://wiki.osdev.org/VGA_Hardware).  There
is an upstream bug in qemu with access to VGA resources with SMM
(System Management Mode) disabled in the guest with `-machine smm=off':

https://gitlab.com/qemu-project/qemu/-/issues/2608

This manifested for us -- because NVMM doesn't support SMM and so
`accel=nvm' implies `smm=off' -- as:

PR pkg/59721: qemu VM's blackscreen over VNC wth -machine q35

I proposed a workaround upstream a few months ago, tested it myself,
and got no feedback upstream.  A few days ago I committed the patch to
pkgsrc, so it will apply to qemu>=10.1.3nb1 and no earlier.  I wonder
whether it makes a difference here.