linux-kernel - Re: [patch V2 06/40] PCI/MSI: Provide static key for parent mask/unmask

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Message-ID: <87bkowcx0z.ffs@tglx>
Date:   Thu, 24 Nov 2022 14:17:00 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <maz@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Will Deacon <will@...nel.org>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Ammar Faizi <ammarfaizi2@...weeb.org>,
        Robin Murphy <robin.murphy@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Vinod Koul <vkoul@...nel.org>, Sinan Kaya <okaya@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Shameerali Kolothum Thodi 
        <shameerali.kolothum.thodi@...wei.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>
Subject: Re: [patch V2 06/40] PCI/MSI: Provide static key for parent
 mask/unmask

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