RE: [Xen-devel] IRQ range in domain 0

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

Something to do with APIC (Advanced Programmable Interrupt Controller) I
think. Here's the output of one system...

           CPU0
  0: 2548267677  local-APIC-edge  timer
  1:      16419    IO-APIC-edge  i8042
  9:          0   IO-APIC-level  acpi
 11:  211183161   IO-APIC-level  ohci_hcd
 14:          2    IO-APIC-edge  ide2
169:  230697393   IO-APIC-level  ide0, ide1
177:  247537790   IO-APIC-level  eth0
201:         63   IO-APIC-level  aic7xxx
209:  185403163   IO-APIC-level  eth1
217:  126336295   IO-APIC-level  eth2
NMI:          0
LOC: 2549847962
ERR:      58866
MIS:          0


> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of John Que
> Sent: Thursday, 25 August 2005 21:13
> To: Xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] IRQ range in domain 0
> 
> Hello,
>   I am running Xen-Unstable on intel x386 , with one CPU ; When
running
> cat /proc/interrupts on Domain 0  I see the following:
> 
>           CPU0
>   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?
> Regards
> John Que.
> 
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