| Message ID | 20200821002424.119492231@linutronix.de (mailing list archive) |
|---|---|
| Headers | show |
| Series | x86, PCI, XEN, genirq ...: Prepare for device MSI | expand |
On 21.08.20 02:24, Thomas Gleixner wrote: > First of all, sorry for the horrible long Cc list, which was > unfortunately unavoidable as this touches the world and some more. > > This patch series aims to provide a base to support device MSI (non > PCI based) in a halfways architecture independent way. > > It's a mixed bag of bug fixes, cleanups and general improvements which > are worthwhile independent of the device MSI stuff. Unfortunately this > also comes with an evil abuse of the irqdomain system to coerce XEN on > x86 into compliance without rewriting XEN from scratch. > > As discussed in length in this mail thread: > > https://lore.kernel.org/r/87h7tcgbs2.fsf@nanos.tec.linutronix.de > > the initial attempt of piggypacking device MSI support on platform MSI > is doomed for various reasons, but creating independent interrupt > domains for these upcoming magic PCI subdevices which are not PCI, but > might be exposed as PCI devices is not as trivial as it seems. > > The initially suggested and evaluated approach of extending platform > MSI turned out to be the completely wrong direction and in fact > platform MSI should be rewritten on top of device MSI or completely > replaced by it. > > One of the main issues is that x86 does not support the concept of irq > domains associations stored in device::msi_domain and still relies on > the arch_*_msi_irqs() fallback implementations which has it's own set > of problems as outlined in > > https://lore.kernel.org/r/87bljg7u4f.fsf@nanos.tec.linutronix.de/ > > in the very same thread. > > The main obstacle of storing that pointer is XEN which has it's own > historical notiion of handling PCI MSI interupts. > > This series tries to address these issues in several steps: > > 1) Accidental bug fixes > iommu/amd: Prevent NULL pointer dereference > > 2) Janitoring > x86/init: Remove unused init ops > > 3) Simplification of the x86 specific interrupt allocation mechanism > > x86/irq: Rename X86_IRQ_ALLOC_TYPE_MSI* to reflect PCI dependency > x86/irq: Add allocation type for parent domain retrieval > iommu/vt-d: Consolidate irq domain getter > iommu/amd: Consolidate irq domain getter > iommu/irq_remapping: Consolidate irq domain lookup > > 4) Consolidation of the X86 specific interrupt allocation mechanism to be as close > as possible to the generic MSI allocation mechanism which allows to get rid > of quite a bunch of x86'isms which are pointless > > x86/irq: Prepare consolidation of irq_alloc_info > x86/msi: Consolidate HPET allocation > x86/ioapic: Consolidate IOAPIC allocation > x86/irq: Consolidate DMAR irq allocation > x86/irq: Consolidate UV domain allocation > PCI: MSI: Rework pci_msi_domain_calc_hwirq() > x86/msi: Consolidate MSI allocation > x86/msi: Use generic MSI domain ops > > 5) x86 specific cleanups to remove the dependency on arch_*_msi_irqs() > > x86/irq: Move apic_post_init() invocation to one place > z86/pci: Reducde #ifdeffery in PCI init code > x86/irq: Initialize PCI/MSI domain at PCI init time > irqdomain/msi: Provide DOMAIN_BUS_VMD_MSI > PCI: vmd: Mark VMD irqdomain with DOMAIN_BUS_VMD_MSI > PCI: MSI: Provide pci_dev_has_special_msi_domain() helper > x86/xen: Make xen_msi_init() static and rename it to xen_hvm_msi_init() > x86/xen: Rework MSI teardown > x86/xen: Consolidate XEN-MSI init > irqdomain/msi: Allow to override msi_domain_alloc/free_irqs() > x86/xen: Wrap XEN MSI management into irqdomain > iommm/vt-d: Store irq domain in struct device > iommm/amd: Store irq domain in struct device > x86/pci: Set default irq domain in pcibios_add_device() > PCI/MSI: Allow to disable arch fallbacks > x86/irq: Cleanup the arch_*_msi_irqs() leftovers > x86/irq: Make most MSI ops XEN private > > This one is paving the way to device MSI support, but it comes > with an ugly and evil hack. The ability of overriding the default > allocation/free functions of an MSI irq domain is useful in general as > (hopefully) demonstrated with the device MSI POC, but the abuse > in context of XEN is evil. OTOH without enough XENology and without > rewriting XEN from scratch wrapping XEN MSI handling into a pseudo > irq domain is a reasonable step forward for mere mortals with severly > limited XENology. One day the XEN folks might make it a real irq domain. > Perhaps when they have to support the same mess on other architectures. > Hope dies last... > > At least the mechanism to override alloc/free turned out to be useful > for implementing the base infrastructure for device MSI. So it's not a > completely lost case. > > 6) X86 specific preparation for device MSI > > x86/irq: Add DEV_MSI allocation type > x86/msi: Let pci_msi_prepare() handle non-PCI MSI > > 7) Generic device MSI infrastructure > > platform-msi: Provide default irq_chip:ack > platform-msi: Add device MSI infrastructure > > 8) Infrastructure for and a POC of an IMS (Interrupt Message > Storm) irq domain and irqchip implementation > > irqdomain/msi: Provide msi_alloc/free_store() callbacks > irqchip: Add IMS array driver - NOT FOR MERGING > > The whole lot is also available from git: > > git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git device-msi > > This has been tested on Intel/AMD/KVM but lacks testing on: > > - HYPERV (-ENODEV) > - VMD enabled systems (-ENODEV) > - XEN (-ENOCLUE) Tested to work in Xen dom0. Network is running fine with eth0 MSI interrupts being routed through Xen. You can add my: Tested-by: Juergen Gross <jgross@suse.com> Juergen
First of all, sorry for the horrible long Cc list, which was unfortunately unavoidable as this touches the world and some more. This patch series aims to provide a base to support device MSI (non PCI based) in a halfways architecture independent way. It's a mixed bag of bug fixes, cleanups and general improvements which are worthwhile independent of the device MSI stuff. Unfortunately this also comes with an evil abuse of the irqdomain system to coerce XEN on x86 into compliance without rewriting XEN from scratch. As discussed in length in this mail thread: https://lore.kernel.org/r/87h7tcgbs2.fsf@nanos.tec.linutronix.de the initial attempt of piggypacking device MSI support on platform MSI is doomed for various reasons, but creating independent interrupt domains for these upcoming magic PCI subdevices which are not PCI, but might be exposed as PCI devices is not as trivial as it seems. The initially suggested and evaluated approach of extending platform MSI turned out to be the completely wrong direction and in fact platform MSI should be rewritten on top of device MSI or completely replaced by it. One of the main issues is that x86 does not support the concept of irq domains associations stored in device::msi_domain and still relies on the arch_*_msi_irqs() fallback implementations which has it's own set of problems as outlined in https://lore.kernel.org/r/87bljg7u4f.fsf@nanos.tec.linutronix.de/ in the very same thread. The main obstacle of storing that pointer is XEN which has it's own historical notiion of handling PCI MSI interupts. This series tries to address these issues in several steps: 1) Accidental bug fixes iommu/amd: Prevent NULL pointer dereference 2) Janitoring x86/init: Remove unused init ops 3) Simplification of the x86 specific interrupt allocation mechanism x86/irq: Rename X86_IRQ_ALLOC_TYPE_MSI* to reflect PCI dependency x86/irq: Add allocation type for parent domain retrieval iommu/vt-d: Consolidate irq domain getter iommu/amd: Consolidate irq domain getter iommu/irq_remapping: Consolidate irq domain lookup 4) Consolidation of the X86 specific interrupt allocation mechanism to be as close as possible to the generic MSI allocation mechanism which allows to get rid of quite a bunch of x86'isms which are pointless x86/irq: Prepare consolidation of irq_alloc_info x86/msi: Consolidate HPET allocation x86/ioapic: Consolidate IOAPIC allocation x86/irq: Consolidate DMAR irq allocation x86/irq: Consolidate UV domain allocation PCI: MSI: Rework pci_msi_domain_calc_hwirq() x86/msi: Consolidate MSI allocation x86/msi: Use generic MSI domain ops 5) x86 specific cleanups to remove the dependency on arch_*_msi_irqs() x86/irq: Move apic_post_init() invocation to one place z86/pci: Reducde #ifdeffery in PCI init code x86/irq: Initialize PCI/MSI domain at PCI init time irqdomain/msi: Provide DOMAIN_BUS_VMD_MSI PCI: vmd: Mark VMD irqdomain with DOMAIN_BUS_VMD_MSI PCI: MSI: Provide pci_dev_has_special_msi_domain() helper x86/xen: Make xen_msi_init() static and rename it to xen_hvm_msi_init() x86/xen: Rework MSI teardown x86/xen: Consolidate XEN-MSI init irqdomain/msi: Allow to override msi_domain_alloc/free_irqs() x86/xen: Wrap XEN MSI management into irqdomain iommm/vt-d: Store irq domain in struct device iommm/amd: Store irq domain in struct device x86/pci: Set default irq domain in pcibios_add_device() PCI/MSI: Allow to disable arch fallbacks x86/irq: Cleanup the arch_*_msi_irqs() leftovers x86/irq: Make most MSI ops XEN private This one is paving the way to device MSI support, but it comes with an ugly and evil hack. The ability of overriding the default allocation/free functions of an MSI irq domain is useful in general as (hopefully) demonstrated with the device MSI POC, but the abuse in context of XEN is evil. OTOH without enough XENology and without rewriting XEN from scratch wrapping XEN MSI handling into a pseudo irq domain is a reasonable step forward for mere mortals with severly limited XENology. One day the XEN folks might make it a real irq domain. Perhaps when they have to support the same mess on other architectures. Hope dies last... At least the mechanism to override alloc/free turned out to be useful for implementing the base infrastructure for device MSI. So it's not a completely lost case. 6) X86 specific preparation for device MSI x86/irq: Add DEV_MSI allocation type x86/msi: Let pci_msi_prepare() handle non-PCI MSI 7) Generic device MSI infrastructure platform-msi: Provide default irq_chip:ack platform-msi: Add device MSI infrastructure 8) Infrastructure for and a POC of an IMS (Interrupt Message Storm) irq domain and irqchip implementation irqdomain/msi: Provide msi_alloc/free_store() callbacks irqchip: Add IMS array driver - NOT FOR MERGING The whole lot is also available from git: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git device-msi This has been tested on Intel/AMD/KVM but lacks testing on: - HYPERV (-ENODEV) - VMD enabled systems (-ENODEV) - XEN (-ENOCLUE) #1 and #2 should be applied unconditionally for obvious reasons #3-5 are wortwhile cleanups which should be done independent of device MSI #6-7 look promising to cleanup the platform MSI implementation independent of #8, but I neither had cycles nor stomache to tackle that. #8 is obviously just for the folks interested in IMS And of course this all started with a 100 lines combo patch to figure out whether this is possible at all with a reasonable effort. 38 patches later ... Thanks, tglx