linux-kernel - Re: [PATCH v3 14/24] genirq/gic-v3-mbi: Remove unused wired MSI mechanics

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Date: Tue, 25 Jun 2024 09:47:09 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Marc Zyngier <maz@...nel.org>
Cc: Shivamurthy Shastri <shivamurthy.shastri@...utronix.de>,
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Subject: Re: [PATCH v3 14/24] genirq/gic-v3-mbi: Remove unused wired MSI
 mechanics

On Tue, Jun 25 2024 at 08:37, Marc Zyngier wrote:
> On Mon, 17 Jun 2024 15:15:44 +0100,
> Thomas Gleixner <tglx@...utronix.de> wrote:
>> just install their special MSI write callback. I don't see any of those
>> setting up LEVEL triggered MSIs.
>> 
>> But then I'm might be missing something. If so can you point me please
>> to the usage instance which actually uses level signaled MSI?
>
> Good question. I'm pretty sure we had *something* at some point that
> used it, or that was planning on using it. I even vividly remember who
> was asking for this.
>
> But either that never really made it upstream, or they decided to move
> away from the kernel setting the MSI up and relied on firmware for
> that (which is fine as long as the device isn't behind an IOMMU).
>
> In the end, it begs the question of what we want to do with this
> feature.  I don't think it is a big deal to keep it around, but maybe
> we should plan for it to be retired. That's independent of this
> series, IMO.

I reworked the conversion so that it keeps it alive. We can remove it
later nevertheless :)

Thanks,

        tglx