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[Xen-devel] IRQ range in domain 0

To: Xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] IRQ range in domain 0
From: John Que <qwejohn@xxxxxxxxx>
Date: Thu, 25 Aug 2005 07:12:53 -0400
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  I am running Xen-Unstable on intel x386 , with one CPU ; When running 
cat /proc/interrupts on Domain 0  I see the following:

  1:       1424        Phys-irq  i8042
  9:          0        Phys-irq  acpi
 14:     421055        Phys-irq  ide0
 15:         16        Phys-irq  ide1
 17:       4419        Phys-irq  eth0
 20:      10884        Phys-irq  ohci_hcd:usb1
 21:          0        Phys-irq  ohci_hcd:usb2
256:          0     Dynamic-irq  ctrl-if
257:      77411     Dynamic-irq  timer0
258:          0     Dynamic-irq  console
259:          0     Dynamic-irq  net-be-dbg
NMI:          0
LOC:          0
ERR:          0
MIS:          0

can I deduce from this that the number of available physical IRQ is
higher than 15?
What is strange to me is that on an ordinary linux kernel (not a
xen-patched kernel ) , there can be up to 15 interrupts,and in all
cases I know, they are in the range 0-14.
I don't remeber I saw a phiyscal interrupt whose number is higher than 14
on a standard x386 platform.

Also according to "Unerstanding the Linux Kernel" book,chapter 4: 
"Tradional PICs are implemented by connecting "in cascade" two
8259A-style external chips.Each chip can handle up to eight different
IRQ input lines. Since the INT output line of the slave PIC is
connected to the IRQ2 pin of the master PIC, the number of available
IRQ lines is limited to 15."

Any ideas?
John Que.

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