Can't build netbsd on Ryzen with non modular kernel

[Ian Clark <mrrooster%gmail.com@localhost>]

Hi all,

I have a very strange issue.

I've recently upgraded my home server to an AMD Ryzen. (the R5 1600
6C/12T) running on a B350 based MSI motherboard.

As part of this process I upgraded to NetBSD 8 as I needed NVMe support.

All is good (apart from having to disable nouveau).

However, I've been unable to build the NetBSD source tree for a while
now. The build fails at a random point with a segmentation fault.

This is using the following build commmand:

$ rm -rf /usr3/build/netbsd-8/* && ./build.sh -N0 -U -T
/usr3/build/netbsd-8/tools -O /usr3/build/netbsd-8/obj -j12 release
kernel=salome kernel=winkleman

(I also build as root, despite having the -U switch specified... )

The failure point is not consistent, and it fails if I build using 1
core or all cores.

I've checked the memory (not extensively, but it's had a pass of
memtest), and otherwise the machine seems stable.

Now, this is where it gets really odd.... I've narrowed this down to
having the following kernel config:

<------------
include "arch/amd64/conf/GENERIC"

no options MODULAR
<------------

If I build a modular kernel or boot GENERIC it's fine, if I build a
non modular kernel i get a random segfault on building.

Weirdly, this /may/ be AMD related, as the same source tree built
under a quad core virtual box VM on my desktop builds fine. (Quad core
VM, emulated SATA HD, around 10G assigned to the VM, same userland,
non modular kernel). The only other difference; but I doubt it's
important is the Ryzen is booted via EFI and the VM the bios boot.
(Bootloader from a 'recentish' current).

Oh, the other thing I've not tried is the crashing AMD kernel on the
VM (The kernels are configured the same but built locally).

The desktop is a Skylake core i5.

Should I raise a PR for this? It all seems rather odd.

Cheers,

Ian