DF-4582/4583 fix-validation run — same KLD harness built WITH the guards
(mirroring DF-4582/fix.diff and DF-4583/fix.diff), kernel flags, guest
DragonFly 6.5-DEVELOPMENT:

  # make clean && make WITH_FIX=1        (cc line verified to carry -DDF4582_FIXED)
  # kldload ./df4582_div0.ko
  # for s in 0 1 2; do sysctl df4582.run=$s; done
  # kldunload df4582_div0.ko

serial console:

DF4582-KMOD: loaded; write sysctl df4582.run=<0|1|2>
DF4582-KMOD: scenario 0: entering verbatim rs690_crtc_bandwidth_compute()
DF4582-KMOD: scenario 0: mode.clock=1048576 kHz sideport=0 pm.sclk=400 igp_sideport_mclk=667
DF4582-FIX: zero divisor avoided at pclk — bailing with safe watermark
DF4582-KMOD: scenario 0: SURVIVED fifo=4 (fixed build?)
DF4582-KMOD: scenario 1: entering verbatim rs690_crtc_bandwidth_compute()
DF4582-KMOD: scenario 1: mode.clock=25175 kHz sideport=1 pm.sclk=400 igp_sideport_mclk=0
DF4582-FIX: zero mclk avoided at rdl — using UMA latency
DF4582-FIX: zero divisor avoided at rdl-mclk — bailing with safe watermark
DF4582-KMOD: scenario 1: SURVIVED fifo=4 (fixed build?)
DF4582-KMOD: scenario 2: entering verbatim rs690_crtc_bandwidth_compute()
DF4582-KMOD: scenario 2: mode.clock=25175 kHz sideport=0 pm.sclk=0 igp_sideport_mclk=667
DF4582-FIX: zero divisor avoided at 1000/sclk — bailing with safe watermark
DF4582-KMOD: scenario 2: SURVIVED fifo=4 (fixed build?)
DF4582-KMOD: unloaded

=> baseline (unpatched same harness): Fatal trap 18 panic (run.log / panic.txt)
   patched: no panic, all three scenarios guarded, clean unload.