UP local APIC is deadly on SMP Athlon

[Ion Badulescu]

A UP kernel compiled with CONFIG_X86_LOCAL_APIC=y dies a very horrible
death on an SMP Athlon motherboard (Tyan S2462 and S2468), flooding the
console with the following messages:

...
masked ExtINT on CPU#0
ESR value before enabling vector: 00000008
ESR value afteC error on CPU8(08)
<6>APIC <6>APIC error PU0: 08(08)
<6C error on CP08(08)
<6>APICor on CPU0: 08
<6>APIC erro CPU0: 08(08)
PIC error on0: 08(08)
<6>Aerror on CPU0:08)
<6>APIC e on CPU0: 08(06>APIC error oU0: 08(08)
<6C error on CPU8(08)
...

[this is a serial console, and the errors are produced faster than the 
console can print them]

The kernel is 2.4.21-pre4, but any recent 2.4/2.5 kernels produce the same 
results: 2.4.20, 2.5.62, and Red Hat's 2.4.18-{18.24}. It's not a 
machine-specific problem, because it shows up on at least 5 different 
machines (all of them dual Athlon, using Tyan MB's). The error message is 
always "APIC error on CPU0: 08(08)".

A bit of binary searching between kernel versions shows that the problem 
was introduced in 2.4.10-pre12.

The IO-APIC option (CONFIG_X86_UP_IOAPIC) does not matter, only the local 
APIC option does. The kernel is compiled for an Athlon (CONFIG_MK7=y and 
everything that implies).

Ideas?

Thanks,
Ion

-- 
  It is better to keep your mouth shut and be thought a fool,
            than to open it and remove all doubt.