Re: hppa lazy FPU switching and QEMU bugs

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

> Date: Mon, 3 Aug 2026 22:57:54 -0400
> From: Thor Lancelot Simon <tls%panix.com@localhost>
> References: <anDzFs-VkFP_opy2%panix.com@localhost>
> 
> On Mon, Aug 03, 2026 at 03:59:18PM -0400, Thor Lancelot Simon wrote:
> > 
> > This host manages QEMU guests running the exact same version of NetBSD
> > on 14 other emulated architectures.  Only hppa blows up like this.  I
> > suppose some day someone will figure out why.
> 
> Actually the problem is not ML-KEM at all nor OpenSSL.  It's a bug in QEMU,
> an information leak that can swap processes' FP registers!

Yes, and we already have an open PR about this:

PR port-hppa/59114: hppa: eager fpu switching for qemu and/or spectre
mitigation
https://gnats.NetBSD.org/59114

I expect there are various tests in /usr/tests/kernel,
/usr/tests/lib/libc, and/or /usr/tests/lib/libm that confirm this
already; we just don't run them on hppa as part of the releng testbed.