SMC SYS-5018A-FTN4 lapic weirdness (9front)

I have a stack of Supermicro SYS-5018A-FTN4 servers upon which  I'm trying to
spin up 9front.

For the most part they work, but one annoyance is the *endless* stream of

  cpu0: lapicerror: 0x00000080

messages the kernel prints out.  Sometimes these originate from cpu1 as well.
The hardware has eight CPU cores.  I don't think I've seen anything from
cpu>1, but in the blizzard of messages, who knows.

I poked a wee bit inside the kernel source, but I don't have time right now
to chase this.  The hardware runs fine, other than refusing to reboot, which
I put down to the usual BIOS ACPI table stupidity.

For the time being I'm going to put a filter on the kprints, but I'm curious
if this sounds familiar to anyone.

Note this happens with both the 32- and 64-bit kernels.

I don't have a quick way to attach sysinfo(1) to this message, but if somebody
can use that I'll figure something out.

--lyndon