event channels

event channels

[jaikumar Ganesh]

Hi
  A newbie to xen here..

I want to add a new event that the xen hypervisor will use to
communicate info to Domain-0. Any pointers as to how I should go about
doing it.

Had a look at the event_channel hypercall and the set_callback
function, but did not get a clear picture..

Thanks
Jaikumar

RE: event channels

[Tian, Kevin]

>From: jaikumar Ganesh
>Sent: 2006年2月27日 8:49
>
>Hi
>  A newbie to xen here..
>
>I want to add a new event that the xen hypervisor will use to
>communicate info to Domain-0. Any pointers as to how I should go about
>doing it.

Normally if the event channel is for communication between domain 
and Xen, it's categorized into VIRQ group. All supported VIRQs are 
listed in xen/include/public/xen.h. Then you need to explicitly register
new added VIRQ to dom0 interrupt sub-system by 
bind_virq_to_irqhandler. Example like drivers/xen/console/console.c. 
If the new VIRQ is meaningful and you'd like to propose it for widely
used, then please send out patch plus description to this mailing
list for discussion.

Thanks,
Kevin

>
>Had a look at the event_channel hypercall and the set_callback
>function, but did not get a clear picture..
>
>Thanks
>Jaikumar
>

Event Channels

[Julian Stecklina]

Hello,

in an application I develop, event channel semantics seem a bit odd to 
me. Consider the following scenario: A Mini-OS binds an unbound port for
domain 0 and issues a notification every second:

	evtchn_alloc_unbound(0, msg_handler, NULL,
			     &port);

	printk("%u %u %u\n", domid, port);

	while (1) {
		sleep(1000);
		notify_remote_via_evtchn(port);
	}

A Linux program running on Domain 0 calls bind_interdomain using domid
and port to obtain local_port and watches for pending notifications:

	evtchn_port_t local_port = xc_evtchn_bind_interdomain(ev, domid, port);

	while (1) {
		evtchn_port_t port;

		port = xc_evtchn_pending(ev);
		printf("%u\n", port);
		xc_evtchn_unmask(ev, port);
	}

Now what I do not understand is, why the Linux program sees exactly one
notification and then indefinitely blocks. Any help on what I may be 
doing wrong is greatly appreciated. This is with xen-3.0.4-testing.

Regards,
Julian

Re: Event Channels

[Mark Williamson]

I don't see anything wrong with your code...  are you sure the minios is 
behaving itself and sending the events?  Have you tried putting printks in 
there to see if it's definitely successfully operating?

Are you sure the value of "port" you're binding in dom0 is correct?  If 
necessary, you could try adding tracing code to the Linux evtchn driver.

I can't quite see what's going wrong from the code you posted, sorry not to be 
more helpful.

Cheers,
Mark

On Friday 12 January 2007 18:33, Julian Stecklina wrote:
> Hello,
>
> in an application I develop, event channel semantics seem a bit odd to
> me. Consider the following scenario: A Mini-OS binds an unbound port for
> domain 0 and issues a notification every second:
>
> 	evtchn_alloc_unbound(0, msg_handler, NULL,
> 			     &port);
>
> 	printk("%u %u %u\n", domid, port);
>
> 	while (1) {
> 		sleep(1000);
> 		notify_remote_via_evtchn(port);
> 	}
>
> A Linux program running on Domain 0 calls bind_interdomain using domid
> and port to obtain local_port and watches for pending notifications:
>
> 	evtchn_port_t local_port = xc_evtchn_bind_interdomain(ev, domid, port);
>
> 	while (1) {
> 		evtchn_port_t port;
>
> 		port = xc_evtchn_pending(ev);
> 		printf("%u\n", port);
> 		xc_evtchn_unmask(ev, port);
> 	}
>
> Now what I do not understand is, why the Linux program sees exactly one
> notification and then indefinitely blocks. Any help on what I may be
> doing wrong is greatly appreciated. This is with xen-3.0.4-testing.
>
> Regards,
> Julian
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

Re: Event Channels

[Brendan Cully]

On Friday, 12 January 2007 at 19:33, Julian Stecklina wrote:
> Hello,
> 
> in an application I develop, event channel semantics seem a bit odd to 
> me. Consider the following scenario: A Mini-OS binds an unbound port for
> domain 0 and issues a notification every second:
> 
> 	evtchn_alloc_unbound(0, msg_handler, NULL,
> 			     &port);
> 
> 	printk("%u %u %u\n", domid, port);
> 
> 	while (1) {
> 		sleep(1000);
> 		notify_remote_via_evtchn(port);
> 	}
> 
> A Linux program running on Domain 0 calls bind_interdomain using domid
> and port to obtain local_port and watches for pending notifications:
> 
> 	evtchn_port_t local_port = xc_evtchn_bind_interdomain(ev, domid, 
> 	port);
> 
> 	while (1) {
> 		evtchn_port_t port;
> 
> 		port = xc_evtchn_pending(ev);
> 		printf("%u\n", port);
> 		xc_evtchn_unmask(ev, port);
> 	}
> 
> Now what I do not understand is, why the Linux program sees exactly one
> notification and then indefinitely blocks. Any help on what I may be 
> doing wrong is greatly appreciated. This is with xen-3.0.4-testing.

According to the interface guide

http://www.cl.cam.ac.uk/research/srg/netos/xen/readmes/interface/interface.html#SECTION00600000000000000000

the event is masked until the receiver clears the notification. I
think you do this by sending a notify back along the same port:

while (1) {
	evtchn_port_t port;
 
	port = xc_evtchn_pending(ev);
	printf("%u\n", port);
	xc_evtchn_notify(ev, port);
	xc_evtchn_unmask(ev, port);
}

Re: Event Channels

[Julian Stecklina]

Mark Williamson wrote:
> I don't see anything wrong with your code...  are you sure the minios is 
> behaving itself and sending the events?  Have you tried putting printks in 
> there to see if it's definitely successfully operating?
> 
> Are you sure the value of "port" you're binding in dom0 is correct?  If 
> necessary, you could try adding tracing code to the Linux evtchn driver.

It seems that the hypercall that ought to perform the notification is 
returning ENOSYS, which is rather strange. I am going to add some 
printk()s to the hypervisor in order to see what is going wrong.

Regards,
Julian

Event Channels

[Koripella Srinivas]

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Hi,
Has any one ever setup event channels between two domU(hvm) guests. or may be a 
hvm guest and a paravirtualized guest?
any code pointers for doing the same?

Thanks





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Re: Event Channels

[Keir Fraser]

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On 4/5/07 21:05, "Koripella Srinivas" <talkwithsrinivas@yahoo.co.in> wrote:

> Has any one ever setup event channels between two domU(hvm) guests. or may be
> a 
> hvm guest and a paravirtualized guest?
> any code pointers for doing the same?

Try looking at the PV-on-HVM Linux drivers (in unmodified_drivers/ directory
of the xen repo).

 -- Keir


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Event Channels

[Srujan D. Kotikela]

Any pointers for how to create event channels?

--
Srujan D. Kotikela