Re: [PATCH 00/16] PCI: MSI parent domain conversion

Nam Cao
2025-07-04T04:53:40Z

On Thu, Jul 03, 2025 at 12:28:01PM -0500, Bjorn Helgaas wrote:
> On Thu, Jun 26, 2025 at 04:47:50PM +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.
> >
> > 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 converts the PCI controller drivers to implement MSI parent
> > domain.
> >
> > drivers/pci/Kconfig | 1 +
> > drivers/pci/controller/Kconfig | 11 +
> > drivers/pci/controller/dwc/Kconfig | 1 +
> > .../pci/controller/dwc/pcie-designware-host.c | 68 ++----
> > drivers/pci/controller/dwc/pcie-designware.h | 1 -
> > drivers/pci/controller/mobiveil/Kconfig | 1 +
> > .../controller/mobiveil/pcie-mobiveil-host.c | 42 ++--
> > .../pci/controller/mobiveil/pcie-mobiveil.h | 1 -
> > drivers/pci/controller/pci-aardvark.c | 59 ++---
> > drivers/pci/controller/pci-hyperv.c | 98 ++++++--
> > drivers/pci/controller/pcie-altera-msi.c | 44 ++--
> > drivers/pci/controller/pcie-brcmstb.c | 44 ++--
> > drivers/pci/controller/pcie-iproc-msi.c | 45 ++--
> > drivers/pci/controller/pcie-mediatek-gen3.c | 67 ++---
> > drivers/pci/controller/pcie-mediatek.c | 46 ++--
> > drivers/pci/controller/pcie-rcar-host.c | 69 ++----
> > drivers/pci/controller/pcie-xilinx-dma-pl.c | 48 ++--
> > drivers/pci/controller/pcie-xilinx-nwl.c | 45 ++--
> > drivers/pci/controller/pcie-xilinx.c | 55 +++--
> > drivers/pci/controller/plda/Kconfig | 1 +
> > drivers/pci/controller/plda/pcie-plda-host.c | 44 ++--
> > drivers/pci/controller/plda/pcie-plda.h | 1 -
> > drivers/pci/controller/vmd.c | 229 +++++++++---------
> > 23 files changed, 504 insertions(+), 517 deletions(-)
>
> Looks good to me, thanks! I think Mani will probably pick this up.
>
> I might have included the specific "legacy MSI domain" thing you're
> replacing. It looks like you're replacing pci_msi_create_irq_domain()
> with msi_create_parent_irq_domain()?

Yes, pci_msi_create_irq_domain() is legacy. We will delete it once
everything is converted.

> Minor merge conflict in pcie-mediatek-gen3.c with dcbea1c7e94e ("PCI:
> mediatek-gen3: Use dev_fwnode() for irq_domain_create_linear()"). No
> problem, we can easily fix that up.

Thanks!

> The "++i" in vmd.c stuck out to me since "i++" is so much more common.

I always do "++i", maybe I'm the weird one..

Best regards,
Nam