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

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

quoted

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/ (local)

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