acpi at irq9 gets ints for pci device at irq20

[Andrew Gallatin]

I have a Tyan Trinity GC-SL (S2707).  After the recent (mid or late
November) improvements to ioapic interrupt handling, irq 20 seems to
be broadcast to ACPI.  

Ie:

% vmstat -i
interrupt                          total       rate
irq4: sio0                           173          6
irq6: fdc0                             4          0
irq8: rtc                           3118        124
irq13: npx0                            1          0
stray irq13                            1          0
irq14: ata0                         1154         46
irq15: ata1                           30          1
irq31: fxp0                          261         10
irq0: clk                           2436         97
Total                               7178        287

# load driver which uses irq20

% sudo kldload gm.ko

# generate some interrupts on irq20

% gm_allsize -g --blocking-no-spin >& /dev/null

% vmstat -i
interrupt                          total       rate
irq4: sio0                          1531         22
irq6: fdc0                             4          0
irq8: rtc                           8780        127
irq9: acpi0                         6430         93
irq13: npx0                            1          0
stray irq13                            1          0
irq14: ata0                         1300         18
irq15: ata1                           30          0
irq20: gm1                          6430         93
irq24: gm2                             1          0
irq31: fxp0                          678          9
irq0: clk                           6858         99
Total                              32044        464

Note how irq20 has the same number of interrupts as the acpi device
at irq9.   

I've tried http://www.freebsd.org/~jhb/patches/acpi_irq.patch, but it
didn't help.

I've left verbose dmesg, mptable, and acpi info at
http://people.freebsd.org/~gallatin/trinity.   This boot was with the
acpi_irq patch appied.

FWIW, this motherboard has always caused acpi to squeal like stuck
pig...

Drew