notification in xen

notification in xen

[Nupur Ghatnekar]

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hey,
For event notification there are 2 functions that i came across.

notify_remote_via_irq(int irq)
notify_remote_via_evtchn(int port)

I tried to use those, but didnt know how to check whether notification has
occurred. Is there a way in which i can check the success of the commands.

Thanks.

-- 

Nupur Ghatnekar

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Re: notification in xen

[Jan Beulich]

>>> On 21.03.12 at 07:20, Nupur Ghatnekar <nupurghatnekar@gmail.com> wrote:
> For event notification there are 2 functions that i came across.
> 
> notify_remote_via_irq(int irq)
> notify_remote_via_evtchn(int port)
> 
> I tried to use those, but didnt know how to check whether notification has
> occurred. Is there a way in which i can check the success of the commands.

While the function could be made return an error indication, there's
little point in doing so - the only possibility for things going wrong is
that you pass in bad arguments.

Jan

Re: notification in xen

[Nupur Ghatnekar]

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On Wed, Mar 21, 2012 at 2:17 PM, Jan Beulich <JBeulich@suse.com> wrote:

> >>> On 21.03.12 at 07:20, Nupur Ghatnekar <nupurghatnekar@gmail.com>
> wrote:
> > For event notification there are 2 functions that i came across.
> >
> > notify_remote_via_irq(int irq)
> > notify_remote_via_evtchn(int port)
> >
> > I tried to use those, but didnt know how to check whether notification
> has
> > occurred. Is there a way in which i can check the success of the
> commands.
>
> While the function could be made return an error indication, there's
> little point in doing so - the only possibility for things going wrong is
> that you pass in bad arguments.
>
> Jan
>
>
>> But is there no other way to find out what happens at the remote end
after
> it receives the notification?

No.

Jan

Then how does inter-domain communication happen??
A simple split device driver implementation

 blkfront wants to access data
-queue a “read request” into memory it shares with blkback
-notify blkback in dom0 using an event channel

blkback experiences an “interrupt” as a result of the event sent to it
-looks in the shared memory to find the request
-executes the read operation
-puts a response in shared memory
-notifies blkfront in the domU using an event channel

blkfront experiences an “interrupt” due to the event sent to it
-completes processing of the new data

How does this notification work?
Could you please explain? if there are any sample codes i can refer to,
that would be great!
-- 

Nupur Ghatnekar

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Re: notification in xen

[Konrad Rzeszutek Wilk]

On Wed, Mar 21, 2012 at 11:50:48AM +0530, Nupur Ghatnekar wrote:
> hey,
> For event notification there are 2 functions that i came across.
> 
> notify_remote_via_irq(int irq)
> notify_remote_via_evtchn(int port)
> 
> I tried to use those, but didnt know how to check whether notification has
> occurred. Is there a way in which i can check the success of the commands.

You should also use 'request_irq' to bind yourself to the IRQ number.
That way your handler would awake when it is done.

Look at how the existing front and backend drivers do it.

> 
> Thanks.
> 
> -- 
> 
> Nupur Ghatnekar

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