linux-kernel - Re: [PATCH v5 0/2] genirq: s390/pci: Migrate MSI interrupts to irqdomain API

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Message-ID: <4046d81fb77672b6d5cf1f17b5de5a0395524e1b.camel@linux.ibm.com>
Date: Fri, 21 Nov 2025 12:03:15 +0100
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Tobias Schumacher <ts@...ux.ibm.com>, Heiko Carstens
 <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>,
        Christian Borntraeger	
 <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Gerald
 Schaefer <gerald.schaefer@...ux.ibm.com>,
        Gerd Bayer
 <gbayer@...ux.ibm.com>, Halil Pasic	 <pasic@...ux.ibm.com>,
        Matthew Rosato
 <mjrosato@...ux.ibm.com>,
        Thomas Gleixner	 <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Farhan Ali
	 <alifm@...ux.ibm.com>
Subject: Re: [PATCH v5 0/2] genirq: s390/pci: Migrate MSI interrupts to
 irqdomain API

On Fri, 2025-11-21 at 06:32 +0100, Tobias Schumacher wrote:
> This patch series reworks the PCIe interrupt handling on s390 by
> migrating it to use a proper MSI parent domain. Introducing a dedicated
> MSI domain hierarchy aligns s390 PCIe support with the generic Linux IRQ
> domain model. Currently s390 is one of the last architectures still using
> the legacy API.
> 
> The migration splits the existing code in the legacy functions
> arch_setup_msi_irqs() and arch_teardown_msi_irqs() into different
> callbacks of the newly created MSI parent domain:
> 
> - zpci_msi_prepare(): prepare the allocation of per-device MSI IRQs.
>       will be called once for each device before allocating individual
>       IRQs and sets up for example the adapter aisb and aibv.
> - zpci_msi_teardown(): reverts the effects of zpci_msi_prepare() and is
>       called after all MSI IRQs are freed.
> - zpci_msi_domain_alloc(): the allocation function for interrupts
> - zpci_msi_domain_free(): revert the effects of zpci_msi_domain_alloc()
> - zpci_compose_msi_msg(): create the MSI message to be written into the
>       corresponding PCI config space.
> 
> * Patch 1 fixes an inconsistency in the irqdomain API. Internally, hw
>   irqs are represented by an unsigned long int (irq_hw_number_t) while
>   the external API in some cases takes an unsigned int as parameter.
>   This fix was required in V2 of the patchset. Due to conceptual changes
>   in patch 2 it is not required anymore for s390, but still seems
>   sensible.
> * Patch 2 implements IRQ domains for s390 PCI
> 
> Since patch 1 changes common APIs, some build tests were done for x86_64
> and arm64. 
> 
> Signed-off-by: Tobias Schumacher <ts@...ux.ibm.com>
> ---

@Heiko, @Vasily, @Alexander, from my point of view this series is ready
to be picked up for the s390 tree and would also benefit from time on
linux-next etc.

Thanks,
Niklas