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

v2: Fix up boot issue with NVMe

Nam Cao (3):
  powerpc/xive: Untangle xive from child interrupt controller drivers
  powerpc/powernv/pci: Switch to use msi_create_parent_irq_domain()
  powerpc/pseries/msi: Switch to msi_create_parent_irq_domain()

 arch/powerpc/include/asm/pci-bridge.h     |   2 -
 arch/powerpc/include/asm/xive.h           |   1 -
 arch/powerpc/platforms/powernv/Kconfig    |   1 +
 arch/powerpc/platforms/powernv/pci-ioda.c |  96 ++++++----------
 arch/powerpc/platforms/pseries/Kconfig    |   1 +
 arch/powerpc/platforms/pseries/msi.c      | 132 ++++++++--------------
 arch/powerpc/sysdev/xive/common.c         |  63 +++++------
 7 files changed, 117 insertions(+), 179 deletions(-)

-- 
2.39.5

On Mon, 11 Aug 2025 11:28:53 +0200, 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.
> 
> [...]

Applied to powerpc/next.

[1/3] powerpc/xive: Untangle xive from child interrupt controller drivers
      https://git.kernel.org/powerpc/c/cc0cc23babc979e399f34f53e4bccf702a389558
[2/3] powerpc/powernv/pci: Switch to use msi_create_parent_irq_domain()
      https://git.kernel.org/powerpc/c/f0ac60e6e311062f1a452d93376055787db4b070
[3/3] powerpc/pseries/msi: Switch to msi_create_parent_irq_domain()
      https://git.kernel.org/powerpc/c/daaa574aba6f9c683408b58a7ab2dc775ece2f98

Thanks

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

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