On Thu, 24 Nov 2022 13:17:00 +0000,
Thomas Gleixner [off-list ref] wrote:

On Thu, Nov 24 2022 at 13:04, Marc Zyngier wrote:

quoted

On Mon, 21 Nov 2022 14:39:36 +0000,

quoted

 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.

If the various irqchips can tell the core code whether they want
things to be masked at the PCI level or at the irqchip level, this
would be a move in the right direction. For the GIC, I'd definitely
want things masked locally.

What I'd like to get rid off is the double masking, as I agree it is
on the "pretty dumb" side of things.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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