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

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Message-Id: <20251112-implement-msi-domain-v1-0-103dd123de14@linux.ibm.com>
Date: Wed, 12 Nov 2025 16:40:43 +0100
From: Tobias Schumacher <ts@...ux.ibm.com>
To: 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>,
        Niklas Schnelle <schnelle@...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,
        Tobias Schumacher <ts@...ux.ibm.com>
Subject: [PATCH 0/2] genirq: s390/pci: Migrate MSI interrupts to irqdomain
 API

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
      correspoding 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 must be fixed to allow for the hwirq encoding used for s390. 
* 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>
---
Tobias Schumacher (2):
      genirq: Change hwirq parameter to irq_hw_number_t
      s390/pci: Migrate s390 IRQ logic to IRQ domain API

 arch/s390/Kconfig           |   1 +
 arch/s390/include/asm/pci.h |   1 +
 arch/s390/pci/pci_bus.c     |   1 +
 arch/s390/pci/pci_irq.c     | 323 +++++++++++++++++++++++++++-----------------
 include/linux/irqdesc.h     |   6 +-
 kernel/irq/irqdesc.c        |   6 +-
 6 files changed, 209 insertions(+), 129 deletions(-)
---
base-commit: 882489402b556fa6d916cba86051276fcc9a8953
change-id: 20251104-implement-msi-domain-dc1ea014580e

Best regards,
-- 
Tobias Schumacher <ts@...ux.ibm.com>