On 14/09/15 18:59, Jake Oshins wrote: >> -----Original Message----- >> From: Marc Zyngier [mailto:marc.zyngier@xxxxxxx] >> Sent: Monday, September 14, 2015 8:01 AM >> To: Jake Oshins <jakeo@xxxxxxxxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx; KY >> Srinivasan <kys@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; >> devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; >> vkuznets@xxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; >> tglx@xxxxxxxxxxxxx; Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx> >> Subject: Re: [PATCH v2 00/12] New paravirtual PCI front-end for Hyper-V >> VMs >> >> Hi Jake, >> >> In the future, please CC me on anything that touches irqdomains, along >> with Jiang Liu as we both co-maintain this piece of code. >> > > Absolutely. Sorry for that omission. > >> On 11/09/15 01:00, jakeo@xxxxxxxxxxxxx wrote: >>> From: Jake Oshins <jakeo@xxxxxxxxxxxxx> >>> >>> The patch series updates the one sent about a month ago in three ways. It >>> integrated with other IRQ domain work done in linux-next in that time, it >>> distributes interrupts to multiple virtual processors in the guest VM, and it >>> incorporates feedback from Thomas Gleixner and others. >>> >>> These patches change the IRQ domain code so that an IRQ domain can >> match on both >>> bus type and on the PCI domain. The IRQ domain match code is modified >> so that >>> IRQ domains can have a "rank," allowing for a default one which matches >> every >>> x86 PC and more specific ones that replace the default. >> >> I'm not really fond of this approach. We already have a way to match an >> IRQ domain, and that's the device node. It looks to me that you're going >> through a lot of pain inventing a new infrastructure to avoid divorcing >> the two. If you could lookup your PCI IRQ domain directly based some >> (non-DT) identifier, and then possibly fallback to the default one, >> would that help? >> >> If so, here's the deal: I have been working on a patch series that >> addresses the above for unrelated reasons (ACPI support on arm64). It >> has been posted twice already: >> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/358768.html >> >> and the latest version is there: >> >> https://git.kernel.org/cgit/linux/kernel/git/maz/arm- >> platforms.git/log/?h=irq/gsi-irq-domain-v3 >> >> I have the feeling that you could replace a lot of your patches with >> this infrastructure. >> >> Thoughts? >> >> M. >> -- > > First, thank you so much for reviewing this. I've read the patch > series above, but I'm sure that I might have misinterpreted it. It > seems to merge the DT and ACPI GSI infrastructure, which I think is a > great idea. I'm not sure, however, that it would, as it stands, > provide what I need here. Please do tell me if I'm wrong. > > The series above allows you to supply different IRQ domains for > separate parts of the ACPI GSI space, which is fine for IRQs which > are actually defined by ACPI. Message-signaled interrupts (MSI), > however, aren't defined by ACPI. ACPI only talks about the routing > of interrupts with pins and traces (or ones which have equivalent > mechanisms like the INTx# protocol in PCI Express.) > > What the older DT layer code allowed was for the PCI driver to look > up an IRQ domain by walking up the device tree looking for a node > that claimed to be an IRQ domain. The match() function on the IRQ > domain allowed it to say that it supported interrupts on PCI buses. > > What's not clear to me is how I would create an IRQ domain that > matches not on ACPI GSI ranges (because ACPI doesn't talk about MSI) > and not just on generic PCI buses. I need to be able to ask for an > IRQ domain "from my parent" which doesn't really exist without the OF > device tree or "for a specific PCI bus domain." That second one is > what I was trying to enable. > > Is there a way to do that with the infrastructure that you're > introducing? The ACPI/GSI stuff is a red herring, and is completely unrelated to the problem you're trying to solve. What I think is of interest to you is contained in the first three patches. In your 4th patch, you have the following code: + pci_domain = pci_domain_nr(bus); + d = irq_find_matching_host(NULL, DOMAIN_BUS_PCI_MSI, &pci_domain); which really feels like you're trying to create a namespace that is parallel to the one defined by the device_node parameter. What I'm trying to do is to be able to replace the device_node by something more generic (at the moment, you can either pass a device_node or some token that the irqdomain subsystem generates for you - see patch #7 for an example). You could pass this token to pci_msi_create_irq_domain (which obviously needs some repainting not to take a device_node), store it in your bus structure, and perform the lookup based on this value. Or store the actual domain there, whatever. What I want to do is really to make this device_node pointer for systems that do not have a DT node to pass there, which is exactly your case (by the look of it, the bus number is your identifier of choice, but I suspect a pointer to an internal structure would be better suited). M. -- Jazz is not dead. It just smells funny... _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
