On Wed, Aug 05, 2020 at 10:36:23PM +0000, Dey, Megha wrote: > Hi Jason, > > > From: Jason Gunthorpe <jgg@xxxxxxxxxxxx> > > Sent: Wednesday, August 5, 2020 3:16 PM > > To: Dey, Megha <megha.dey@xxxxxxxxx> > > Cc: Marc Zyngier <maz@xxxxxxxxxx>; Jiang, Dave <dave.jiang@xxxxxxxxx>; > > vkoul@xxxxxxxxxx; bhelgaas@xxxxxxxxxx; rafael@xxxxxxxxxx; > > gregkh@xxxxxxxxxxxxxxxxxxx; tglx@xxxxxxxxxxxxx; hpa@xxxxxxxxx; > > alex.williamson@xxxxxxxxxx; Pan, Jacob jun <jacob.jun.pan@xxxxxxxxx>; Raj, > > Ashok <ashok.raj@xxxxxxxxx>; Liu, Yi L <yi.l.liu@xxxxxxxxx>; Lu, Baolu > > <baolu.lu@xxxxxxxxx>; Tian, Kevin <kevin.tian@xxxxxxxxx>; Kumar, Sanjay K > > <sanjay.k.kumar@xxxxxxxxx>; Luck, Tony <tony.luck@xxxxxxxxx>; Lin, Jing > > <jing.lin@xxxxxxxxx>; Williams, Dan J <dan.j.williams@xxxxxxxxx>; > > kwankhede@xxxxxxxxxx; eric.auger@xxxxxxxxxx; parav@xxxxxxxxxxxx; > > Hansen, Dave <dave.hansen@xxxxxxxxx>; netanelg@xxxxxxxxxxxx; > > shahafs@xxxxxxxxxxxx; yan.y.zhao@xxxxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; > > Ortiz, Samuel <samuel.ortiz@xxxxxxxxx>; Hossain, Mona > > <mona.hossain@xxxxxxxxx>; dmaengine@xxxxxxxxxxxxxxx; linux- > > kernel@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; > > kvm@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH RFC v2 02/18] irq/dev-msi: Add support for a new DEV_MSI > > irq domain > > > > On Wed, Aug 05, 2020 at 07:18:39PM +0000, Dey, Megha wrote: > > > > > Hence we will only have one create_dev_msi_domain which can be called > > > by any device driver that wants to use the dev-msi IRQ domain to > > > alloc/free IRQs. It would be the responsibility of the device driver > > > to provide the correct device and update the dev->msi_domain. > > > > I'm not sure that sounds like a good idea, why should a device driver touch dev- > > >msi_domain? > > > > There was a certain appeal to the api I suggested by having everything related to > > setting up the new IRQs being in the core code. > > The basic API to create the dev_msi domain would be : > > struct irq_domain *create_dev_msi_irq_domain(struct irq_domain *parent) > > This can be called by devices according to their use case. > > For e.g. in dsa case, it is called from the irq remapping driver: > iommu->ir_dev_msi_domain = create_dev_msi_domain(iommu->ir_domain) > > and from the dsa mdev driver: > p_dev = get_parent_pci_dev(dev); > iommu = device_to_iommu(p_dev); > > dev->msi_domain = iommu->ir_dev_msi_domain; > > So we are creating the domain in the IRQ remapping domain which can be used by other devices which want to have the same IRQ parent domain and use dev-msi APIs. We are only updating that device's msi_domain to the already created dev-msi domain in the driver. > > Other devices (your rdma driver etc) can create their own dev-msi domain by passing the appropriate parent IRq domain. > > We cannot have this in the core code since the parent domain cannot > be the same? Well, I had suggested to pass in the parent struct device, but it could certainly use an irq_domain instead: platform_msi_assign_domain(dev, device_to_iommu(p_dev)->ir_domain); Or platform_msi_assign_domain(dev, pdev->msi_domain) ? Any maybe the natural expression is to add a version of platform_msi_create_device_domain() that accepts a parent irq_domain() and if the device doesn't already have a msi_domain then it creates one. Might be too tricky to manage lifetime of the new irq_domain though.. It feels cleaner to me if everything related to this is contained in the platform_msi and the driver using it. Not sure it makes sense to involve the iommu? Jason
