On 2014/11/21 9:46, Thomas Gleixner wrote: > On Fri, 21 Nov 2014, Yijing Wang wrote: >> On 2014/11/21 0:31, Marc Zyngier wrote: >>> Bjorn, Yijing, >>> >>> I've just realized that patch c167caf8d174 (PCI/MSI: Remove useless >>> bus->msi assignment) completely breaks MSI on arm64 when using the new >>> MSI stacked domain: >> >> Sorry, this is my first part to refactor MSI related code, now how >> to get pci msi_controller depends arch >> functions(pcibios_msi_controller() or arch_setup_msi_irq()), we are >> working on generic pci_host_bridge, after that, we could eventually >> eliminate MSI arch functions and find pci dev 's msi controller by >> pci_host_bridge->get_msi_controller(). > > The main question is why you think that pci_host_bridge is the proper > place to store that information. > > On x86 we have DMAR units associated to a single device. Each DMAR > unit is a seperate MSI irq domain. > > Can you guarantee that the pci_host_bridge is the right point to > provide the association of the device to the irq domain? > > So the real question is: > > What is the association level requirement to properly identify the > irqdomain for a specific device on any given architecture with and > without IOMMU, interrupt redirection etc. > > To be honest: I don't know. > > My gut feeling tells me that it's at the device level, but I really > leave that decision to the experts in that field. Hi Thomas and Yijing, Since we are allocating interrupts for a PCI device, it's natural to get irqdomain from the PCI device itself. If we try to get irqdomain from a PCI bus or host bridge like pci_get_msi_irqdomain(bus or hostbridge), it may fail for x86 because x86 may build per-device irqdomain theoretically. So the preferred interface prototype is: pci_get_msi_irqdomain(pci_dev) or pcibios_msi_controller(pci_dev) It's flexible enough. For architectures on which irqdomain is associated with PCI bus or host bridge, you could get the bus or host bridge from pci_dev. And it won't cause extra computation because you always need to get bus or host bridge from the pci_dev. Regards! Gerry > > Thanks, > > tglx > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
