port-mips/59283: pmax testbed doesn't have fp exception traps

[campbell+netbsd%mumble.net@localhost]

>Number:         59283
>Category:       port-mips
>Synopsis:       pmax testbed doesn't have fp exception traps
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-mips-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 12 17:40:01 +0000 2025
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The PmaxBSD FPExceptionalism
>Environment:
>Description:
Test case: kernel/t_trapsignal/fpe_handle

Duration: 2.074219 seconds
Termination reason

FAILED: atf-check failed; see the output of the test for details
Standard output stream

Executing command [ /usr/tests/kernel/h_segv fpe handle ]

Standard error stream

Fail: stderr does not match expected value
--- /tmp/inline.M9pIaL	2025-04-12 07:22:28.507812500 +0000
+++ /tmp/check.QvDSU1/stderr	2025-04-12 07:22:28.460937500 +0000
@@ -1 +0,0 @@
-got 8

Test case: kernel/t_trapsignal/fpe_handle_recurse

Duration: 0.601562 seconds
Termination reason

FAILED: atf-check failed; see the output of the test for details
Standard output stream

Executing command [ /usr/tests/kernel/h_segv fpe handle recurse ]

Standard error stream

Fail: program did not receive a signal
...

https://releng.netbsd.org/b5reports/pmax/2025/2025.04.11.04.54.02/test.html#kernel_t_trapsignal_fpe_handle

The MIPS architecture supports floating-point exception traps but it looks like they aren't happening on the pmax testbed.
>How-To-Repeat:
cd /usr/tests/lib/libc/gen
atf-run t_fpclassify | atf-report
>Fix:
Yes, please!

Not sure if this is a qemu bug or a hardware bug or a NetBSD kernel bug in configuring the FPU.  Guessing it's probably a qemu bug and might be helped by adding if (isQEMU()) { atf_tc_expect_fail("PR ...") }.