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

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Message-ID: <88359a18-7b82-41b5-b000-d4df837efd23@linux.ibm.com>
Date: Sat, 6 Sep 2025 17:18:57 +0530
From: Madhavan Srinivasan <maddy@...ux.ibm.com>
To: Thomas Gleixner <tglx@...utronix.de>, Nam Cao <namcao@...utronix.de>,
        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
Subject: Re: [PATCH v2 0/3] powerpc: Cleanup and convert to MSI parent domain



On 9/3/25 7:37 PM, Thomas Gleixner wrote:
> 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?

Yes, sorry for the delay,
Will add this to my next after the test

Maddy

> 
> Thanks,
> 
>         tglx