linux-kernel - Re: [PATCH v2 0/3] powerpc: Cleanup and convert to MSI parent domain

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Message-ID: <87y0qvy6hb.ffs@tglx>
Date: Wed, 03 Sep 2025 16:07:44 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Nam Cao <namcao@...utronix.de>, Madhavan Srinivasan
 <maddy@...ux.ibm.com>, Michael Ellerman <mpe@...erman.id.au>, Nicholas
 Piggin <npiggin@...il.com>, Christophe Leroy
 <christophe.leroy@...roup.eu>, Marc Zyngier <maz@...nel.org>, Gautam
 Menghani <gautam@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org
Cc: Nam Cao <namcao@...utronix.de>
Subject: Re: [PATCH v2 0/3] powerpc: Cleanup and convert to MSI parent domain

On Mon, Aug 11 2025 at 11:28, Nam Cao wrote:

> The initial implementation of PCI/MSI interrupt domains in the hierarchical
> interrupt domain model used a shortcut by providing a global PCI/MSI
> domain.
>
> This works because the PCI/MSI[X] hardware is standardized and uniform, but
> it violates the basic design principle of hierarchical interrupt domains:
> Each hardware block involved in the interrupt delivery chain should have a
> separate interrupt domain.
>
> For PCI/MSI[X], the interrupt controller is per PCI device and not a global
> made-up entity.
>
> Unsurprisingly, the shortcut turned out to have downsides as it does not
> allow dynamic allocation of interrupt vectors after initialization and it
> prevents supporting IMS on PCI. For further details, see:
>
> https://lore.kernel.org/lkml/20221111120501.026511281@linutronix.de/
>
> The solution is implementing per device MSI domains, this means the
> entities which provide global PCI/MSI domain so far have to implement MSI
> parent domain functionality instead.
>
> This series:
>
>    - Untangle XIVE driver from Powernv and Pseries drivers
>
>    - Convert the Powernv and Pseries drivers to implement MSI parent domain
>      functionality

Polite reminder to the PPC folks. Can we please get this moving so we
can finally cleanup the pci_msi_create_irq_domain() leftovers?

Thanks,

        tglx