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Date: Sun, 3 May 2020 17:25:28 -0700 From: "Dey, Megha" <megha.dey@...ux.intel.com> To: Jason Gunthorpe <jgg@...pe.ca> Cc: Dave Jiang <dave.jiang@...el.com>, vkoul@...nel.org, maz@...nel.org, bhelgaas@...gle.com, rafael@...nel.org, gregkh@...uxfoundation.org, tglx@...utronix.de, hpa@...or.com, alex.williamson@...hat.com, jacob.jun.pan@...el.com, ashok.raj@...el.com, yi.l.liu@...el.com, baolu.lu@...el.com, kevin.tian@...el.com, sanjay.k.kumar@...el.com, tony.luck@...el.com, jing.lin@...el.com, dan.j.williams@...el.com, kwankhede@...dia.com, eric.auger@...hat.com, parav@...lanox.com, dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org, linux-pci@...r.kernel.org, kvm@...r.kernel.org Subject: Re: [PATCH RFC 04/15] drivers/base: Add support for a new IMS irq domain On 5/3/2020 3:46 PM, Jason Gunthorpe wrote: > On Sun, May 03, 2020 at 03:40:44PM -0700, Dey, Megha wrote: >> On 5/3/2020 3:25 PM, Jason Gunthorpe wrote: >>> On Fri, May 01, 2020 at 03:30:02PM -0700, Dey, Megha wrote: >>>> Hi Jason, >>>> >>>> On 4/23/2020 1:11 PM, Jason Gunthorpe wrote: >>>>> On Tue, Apr 21, 2020 at 04:34:11PM -0700, Dave Jiang wrote: >>>>>> diff --git a/drivers/base/ims-msi.c b/drivers/base/ims-msi.c >>>>>> new file mode 100644 >>>>>> index 000000000000..738f6d153155 >>>>>> +++ b/drivers/base/ims-msi.c >>>>>> @@ -0,0 +1,100 @@ >>>>>> +// SPDX-License-Identifier: GPL-2.0-only >>>>>> +/* >>>>>> + * Support for Device Specific IMS interrupts. >>>>>> + * >>>>>> + * Copyright © 2019 Intel Corporation. >>>>>> + * >>>>>> + * Author: Megha Dey <megha.dey@...el.com> >>>>>> + */ >>>>>> + >>>>>> +#include <linux/dmar.h> >>>>>> +#include <linux/irq.h> >>>>>> +#include <linux/mdev.h> >>>>>> +#include <linux/pci.h> >>>>>> + >>>>>> +/* >>>>>> + * Determine if a dev is mdev or not. Return NULL if not mdev device. >>>>>> + * Return mdev's parent dev if success. >>>>>> + */ >>>>>> +static inline struct device *mdev_to_parent(struct device *dev) >>>>>> +{ >>>>>> + struct device *ret = NULL; >>>>>> + struct device *(*fn)(struct device *dev); >>>>>> + struct bus_type *bus = symbol_get(mdev_bus_type); >>>>>> + >>>>>> + if (bus && dev->bus == bus) { >>>>>> + fn = symbol_get(mdev_dev_to_parent_dev); >>>>>> + ret = fn(dev); >>>>>> + symbol_put(mdev_dev_to_parent_dev); >>>>>> + symbol_put(mdev_bus_type); >>>>> >>>>> No, things like this are not OK in the drivers/base >>>>> >>>>> Whatever this is doing needs to be properly architected in some >>>>> generic way. >>>> >>>> Basically what I am trying to do here is to determine if the device is an >>>> mdev device or not. >>> >>> Why? mdev devices are virtual they don't have HW elements. >> >> Hmm yeah exactly, since they are virtual, they do not have an associated IRQ >> domain right? So they use the irq domain of the parent device.. >> >>> >>> The caller should use the concrete pci_device to allocate >>> platform_msi? What is preventing this? >> >> hmmm do you mean to say all platform-msi adhere to the rules of a PCI >> device? > > I mean where a platform-msi can work should be defined by the arch, > and probably is related to things like having an irq_domain attached > > So, like pci, drivers must only try to do platfor_msi stuff on > particular devices. eg on pci_device and platform_device types. > > Even so it may not even work, but I can't think of any reason why it > should be made to work on a virtual device like mdev. > >> The use case if when we have a device assigned to a guest and we >> want to allocate IMS(platform-msi) interrupts for that >> guest-assigned device. Currently, this is abstracted through a mdev >> interface. > > And the mdev has the pci_device internally, so it should simply pass > that pci_device to the platform_msi machinery. hmm i am not sure I follow this. mdev has a pci_device internally? which struct are you referring to here? mdev is merely a micropartitioned PCI device right, which no real PCI resource backing. I am not how else we can find the IRQ domain associated with an mdev.. > > This is no different from something like pci_iomap() which must be > used with the pci_device. > > Jason >
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