Interrupts in Xen: Dynamic-irq and Phys-irq

[John Que <qwejohn@gmail.com>]

Hello, 
  I am running the xen-unstable (linux 2.6.11 kernel) after building
it from source.

I had noticed that , when starting a new domain, and running:

cat /proc/interrupts, it show many irq which are of type "Dynamic-irq":

for example:
.....
259:        234     Dynamic-irq  blkif
.....

I had traced down it down in xen source  to dynirq_type struct in: 
linux-2.6.11-xen-sparse/arch/xen/kernel/evtchn.c:

static struct hw_interrupt_type dynirq_type = 
  {
  "Dynamic-irq",
  startup_dynirq,
  shutdown_dynirq,
  enable_dynirq,
	...
	...
	};
	
 I saw a usage of this struct (might it be the only usage ?) 
 in the init_IRQ() method, in this evtchn.c:
  ......
 irq_desc[dynirq_to_irq(i)].handler = &dynirq_type; 
 .......
 
 irq_desc is an instance irq_desc struct (in irq.h) ; 
 It's  handler member is a pointer to hw_irq_controller, which is in fact 
 hw_irq_controller.  

 ( in irq.h .there is a "typedef struct hw_interrupt_type  hw_irq_controller");
 
 Does anybody know and can explain in few sentences what is this Dynamic-irq? 
 What is it's use? 
 
 The "Dynamic-irq" also appears in Dom0 (for example, when you run 
"cat /proc/interrupts" and look at the  line containing "ctrl-if" or "console").

Besides it, In dom0 there is also "Phys-irq" ; for examples,after 
running "cat /proc/interruupts" in line containing "eth0" or "ide0" or "ide1". 

what is the difference between these 2 types of interrupts ? 

 Regards,
John Q.