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Re: [XEN PATCH v1 4/5] xen/arm: allow dynamically assigned SGI handlers


  • To: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
  • From: Michal Orzel <michal.orzel@xxxxxxx>
  • Date: Thu, 11 Apr 2024 08:44:32 +0200
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  • Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxx>, <patches@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
  • Delivery-date: Thu, 11 Apr 2024 06:44:46 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

Hi Jens,

On 11/04/2024 08:12, Jens Wiklander wrote:
> 
> 
> Hi Michal,
> 
> On Wed, Apr 10, 2024 at 3:24 PM Michal Orzel <michal.orzel@xxxxxxx> wrote:
>>
>> Hi Jens,
>>
>> On 09/04/2024 17:36, Jens Wiklander wrote:
>>>
>>>
>>> Updates so request_irq() can be used with a dynamically assigned SGI irq
>>> as input.
>> At this point it would be handy to mention the use case for which you need 
>> to add this support
> 
> OK, I'll add something like:
> This prepares for a later patch where an FF-A schedule receiver
> interrupt handler is installed for an SGI generated by the secure
> world.
ok

> 
>>
>>>
>>> gic_route_irq_to_xen() don't gic_set_irq_type() for SGIs since they have
>>> their type assigned earlier during boot
>> Could you elaborate more on that? Do you mean that SGIs are always edge 
>> triggered and there's no need
>> for setting the type?
> 
> Yes, see https://developer.arm.com/documentation/ihi0069/h
> 4.4 Software Generated Interrupts
> SGIs are typically used for inter-processor communication, and are
> generated by a write to an SGI register in the
> GIC. SGIs can be either Group 0 or Group 1 interrupts, and they can
> support only edge-triggered behavior.
Exactly. But you wrote "have their type assigned earlier during boot" which is 
not true.
There is no write to ICFGR0 in Xen codebase. They are implicitly edge triggered.
So I would write:
"... for SGIs since they are always edge triggered"

~Michal



 


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