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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Marc Zyngier <maz@kernel.org>
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Subject: Re: [patch V2 06/40] PCI/MSI: Provide static key for parent
 mask/unmask
In-Reply-To: <8635a8o65q.wl-maz@kernel.org>
References: <20221121135653.208611233@linutronix.de>
 <20221121140048.659849460@linutronix.de> <8635a8o65q.wl-maz@kernel.org>
Date:   Thu, 24 Nov 2022 14:17:00 +0100
Message-ID: <87bkowcx0z.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Thu, Nov 24 2022 at 13:04, Marc Zyngier wrote:
> On Mon, 21 Nov 2022 14:39:36 +0000,
>>  static void pci_mask_msi(struct irq_data *data)
>>  {
>>  	struct msi_desc *desc = irq_data_get_msi_desc(data);
>>  
>>  	pci_msi_mask(desc, BIT(data->irq - desc->irq));
>> +	cond_mask_parent(data);
>
> I find this a bit odd. If anything, I'd rather drop the masking at the
> PCI level and keep it local to the interrupt controller, because this
> is likely to be more universal than the equivalent PCI operation
> (think multi-MSI, for example, which cannot masks individual MSIs).
>
> Another thing is that the static key is a global state. Nothing says
> that masking one way or the other is a universal thing, specially when
> you have multiple interrupt controllers dealing with MSIs in different
> ways. For example, GICv3 can use both the ITS and the GICv3-MBI frame
> at the same time for different PCI RC. OK, they happen to deal with
> MSIs in the same way, but you hopefully get my point.

I'm fine with dropping that. I did this because basically all of the
various ARM PCI/MSI domain implementation have a copy of the same
functions. Some of them have pointlessly the wrong order because copy &
pasta is so wonderful....

So the alternative solution is to provide _ONE_ set of correct callbacks
and let the domain initialization code override the irq chip callbacks
of the default PCI/MSI template.

Thanks,

        tglx