Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757386AbaLIO7z (ORCPT ); Tue, 9 Dec 2014 09:59:55 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:47055 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757211AbaLIO7x (ORCPT ); Tue, 9 Dec 2014 09:59:53 -0500 Message-ID: <54870E56.7000909@arm.com> Date: Tue, 09 Dec 2014 14:59:34 +0000 From: Marc Zyngier User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.2.0 MIME-Version: 1.0 To: Jiang Liu , Yijing Wang , Bjorn Helgaas , Thomas Gleixner CC: "linux-arm-kernel@lists.infradead.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Will Deacon , "suravee.suthikulpanit@amd.com" Subject: Re: [PATCH 2/6] PCI/MSI: add hooks to populate the msi_domain field References: <1418069543-21969-1-git-send-email-marc.zyngier@arm.com> <1418069543-21969-3-git-send-email-marc.zyngier@arm.com> <5486585B.40000@huawei.com> <5486C8BA.8030608@arm.com> <5486E3BF.70703@huawei.com> <5486E747.4010804@arm.com> <5486EF4E.5020704@linux.intel.com> <5487012B.4040505@arm.com> <54870302.5050703@linux.intel.com> <548706E9.8080701@arm.com> <548708CC.5000405@linux.intel.com> In-Reply-To: <548708CC.5000405@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/12/14 14:35, Jiang Liu wrote: > On 2014/12/9 22:27, Marc Zyngier wrote: >> On 09/12/14 14:11, Jiang Liu wrote: >>> On 2014/12/9 22:03, Marc Zyngier wrote: >>>> Hi Gerry, >>>> >>>> On 09/12/14 12:47, Jiang Liu wrote: >>>>> On 2014/12/9 20:12, Marc Zyngier wrote: >>>>>> Yijing, >>>>>> >>>>>> On 09/12/14 11:57, Yijing Wang wrote: >>>>>>>>>> +void __weak pcibios_set_phb_msi_domain(struct pci_bus *bus) >>>>>>>>>> +{ >>>>>>>>>> +} >>>>>>>>>> + >>>>>>>>>> +static void pci_set_bus_msi_domain(struct pci_bus *bus) >>>>>>>>>> +{ >>>>>>>>>> + struct pci_dev *bridge = bus->self; >>>>>>>>>> + >>>>>>>>>> + if (!bridge) >>>>>>>>>> + pcibios_set_phb_msi_domain(bus); >>>>>>>>>> + else >>>>>>>>>> + dev_set_msi_domain(&bus->dev, dev_get_msi_domain(&bridge->dev)); >>>>>>>>>> +} >>>>>>>>> >>>>>>>>> >>>>>>>>> Hi Marc, we can not assume pci devices under same phb share the same msi irq domain, >>>>>>>>> now in x86, pci devices under the same phb may associate different msi irq domain. >>>>>>> >>>>>>> Hi Marc, >>>>>>> >>>>>>>> >>>>>>>> Well, this is not supposed to be a perfect solution yet, but instead a >>>>>>>> basis for discussion. What I'd like to find out is: >>>>>>>> >>>>>>>> - What is the minimum granularity for associating a device with its MSI >>>>>>>> domain in existing platforms? >>>>>>> >>>>>>> PCI device, after Gerry's msi irq domain patchset which now in linux-next, >>>>>>> in x86, we will find msi irq domain by pci_dev. >>>>>> >>>>>> Are you *really* associating the MSI domain on a per pci-device basis? >>>>>> That is, you have devices on the same PCI bus talking to different MSI hw? >>>>> Hi Marc, >>>>> This is a little wild:( >>>>> On x86 platform with Intel VT-d(not the case for AMD-v), >>>>> interrupt remapping is tight to DMA remapping (IOMMU) unit. >>>>> For most common cases, IOMMU unit manages PCI bus and its sub-hierarchy. >>>>> But it may also manage a specific PCI device. This is typically used to >>>>> provide QoS for audio device by using dedicated IOMMU unit to avoid >>>>> resource contention on DMA remapping tables. BIOS uses ACPI table to >>>>> report PCI bus/device to IOMMU unit mapping relationship. (To be honest, >>>>> I have no really experience with such a hardware platform yet, just for >>>>> theoretical analysis) >>>>> On the other hand, we now support hierarchy irqdomain. So to >>>>> support per-PCI IOMMU unit case, we need maintain irqdomain at PCI >>>>> device level. >>>>> This piece of code from your [4/6] is flexible enough, which >>>>> retrieves msi_domain from PCI device, then fallback to PCI bus, >>>>> then fallback to platform specific method. >>>>> domain = dev_get_msi_domain(&dev->dev); >>>>> if (!domain && dev->bus->msi) >>>>> domain = dev->bus->msi->domain; >>>>> if (!domain) >>>>> domain = arch_get_pci_msi_domain(dev); >>>> >>>> OK. But what I'd really like to see is a way to setup the >>>> device<->domain binding as early as possible, without having to use more >>>> conditional code in pci_msi_get_domain. >>>> >>>> IOW, can we do something similar to what pci_set_bus_msi_domain and >>>> pci_set_msi_domain do in this patch? >>> Hi Marc, >>> I have checked x86 code, we could set pci_dev->msi_domain >>> when creating PCI devices, just need to find some hook points >>> into PCI core next step. If arch code doesn't set pci_dev->msi_domain, >>> PCI MSI core may provide a default way to set pci_dev->msi_domain. >>> This may make the implementation simpler, I guess:) >> >> Right. So following your earlier suggestion, I could make >> pci_set_msi_domain a weak symbol and let arch code override this. >> >> My preference would have been to have arch code to create a set of >> arch-independent data structures describing the topology, and use that >> for everything, but maybe that's a bit ambitious for a start. >> >> I'll rework the series to make the symbols weak. > Hi Marc, > I think we may not need the weak symbol at all. With following > draft patch, the PCI MSI core may simply do: > if (pci_dev->dev.msi_domain == NULL) > dev_set_msi_domain(&dev->dev, > dev_get_msi_domain(&dev->bus->dev)); > ----------------------------------------------------------------------- > Note: the patch won't pass compilation, just to show the key idea:) > > diff --git a/arch/x86/kernel/apic/msi.c b/arch/x86/kernel/apic/msi.c > index da163da5fdee..8147d25d4349 100644 > --- a/arch/x86/kernel/apic/msi.c > +++ b/arch/x86/kernel/apic/msi.c > @@ -67,6 +67,23 @@ static struct irq_chip pci_msi_controller = { > .flags = IRQCHIP_SKIP_SET_WAKE, > }; > > +struct irq_domain *x86_get_pci_msi_domain(struct pci_dev *dev) > +{ > + struct irq_domain *domain; > + struct irq_alloc_info info; > + > + init_irq_alloc_info(&info, NULL); > + info.type = X86_IRQ_ALLOC_TYPE_MSI; > + info.msi_dev = dev; > + domain = irq_remapping_get_irq_domain(&info); > + if (domain == NULL) > + domain = msi_default_domain; > + if (domain == NULL) > + domain = ERR_PTR(-ENOSYS); > + > + return domain; > +} > + > int native_setup_msi_irqs(struct pci_dev *dev, int nvec, int type) > { > struct irq_domain *domain; > diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c > index 7b20bccf3648..a26f30a8bb8f 100644 > --- a/arch/x86/pci/common.c > +++ b/arch/x86/pci/common.c > @@ -652,6 +652,9 @@ int pcibios_add_device(struct pci_dev *dev) > pa_data = data->next; > iounmap(data); > } > + > + dev->dev.msi_domain = x86_get_pci_msi_domain(dev); > + > return 0; > } Right. So you set the msi_domain using the pcibios_add_device callback. That will require some minimal surgery (the call to pci_set_msi_domain happens before the pcibios call, so it needs to be relocated after), but that seems like a sensible solution to me. Thanks! M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/