Re: [Xen-devel] [PATCH v4 16/24] xen: clear IRQ_NOAUTOEN and IRQ_NOREQUEST

[Marc Zyngier <marc.zyngier@xxxxxxx>]

On 14/09/12 15:13, Stefano Stabellini wrote:
> On Fri, 14 Sep 2012, Marc Zyngier wrote:
>> On 14/09/12 12:13, Stefano Stabellini wrote:
>>> Reset the IRQ_NOAUTOEN and IRQ_NOREQUEST flags that are enabled by
>>> default on ARM. If IRQ_NOAUTOEN is set, __setup_irq doesn't call
>>> irq_startup, that is responsible for calling irq_unmask at startup time.
>>> As a result event channels remain masked.
>>>
>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>>> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>>> ---
>>>  drivers/xen/events.c |    1 +
>>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
>>> index 5ecb596..8ffb7b7 100644
>>> --- a/drivers/xen/events.c
>>> +++ b/drivers/xen/events.c
>>> @@ -836,6 +836,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
>>>             struct irq_info *info = info_for_irq(irq);
>>>             WARN_ON(info == NULL || info->type != IRQT_EVTCHN);
>>>     }
>>> +   irq_clear_status_flags(irq, IRQ_NOREQUEST|IRQ_NOAUTOEN);
>>
>> This one just sent a shiver down my spine. Are you doing this for a PPI?
> 
> Not really: even though there is just one source of event notifications
> (that is a PPI), we have many event channels. When a domain receives a
> notification (via the PPI), it checks on a bitmask to which event channel
> it corresponds. From the Linux point of view every event channel is a
> Linux irq belonging to the xen_dynamic_chip (see
> drivers/xen/events.c:xen_dynamic_chip).
> 
> So here I am not doing this for the one PPI, but I am doing this for
> every Linux irq (of chip xen_dynamic_chip) that represents an event
> channel.

So this is some sort of secondary interrupt controller, cascaded into
your GIC emulation, and this patch only affects the xen_dynamic_chip?

        M.
-- 
Jazz is not dead. It just smells funny...


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