Re: [Xen-devel] [PATCH v5 19/22] hvm/params: Add a new delivery type for event-channel in HVM_PARAM_CALLBACK_IRQ

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Mar 16, 2016 at 04:34:19PM +0000, Julien Grall wrote:
> Hi Konrad,
> 
> On 04/03/2016 21:19, Konrad Rzeszutek Wilk wrote:
> >Anyhow what I am wondering if there are some semantincs when it comes to PPI
> >and it being able to 'mask' an vector until it exits or such? If so
> >you should document that.
> 
> I'm not sure to understand what you are asking.
> 
> Xen takes advantage of the virtual interrupt controller to notify the guest
> of new pending event channels.
> 
> The life cycle (mask/eoi) of the interrupt associated to the notification is
> handled by the interrupt controller. The interrupt can't be re-entrant but
> we may receive spurious notification.

Excellent. That is what I wanted to know. It would be good to make
sure that is mentioned in the header file.

> 
> AFAIK, there is no specific semantics. Stefano, can you confirm it?

Because on x86 the vector callback bypasses the interrupt controller and
injects the vector using the mechanism that is usually used for exceptions
(or emulating software interrupts).

> 
> Regards,
> 
> -- 
> Julien Grall

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