Hi Jason, > -----Original Message----- > From: Jason Gunthorpe <jgg@xxxxxxxxxxxx> > Sent: Wednesday, August 5, 2020 5:19 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 Thu, Aug 06, 2020 at 12:13:24AM +0000, Dey, Megha wrote: > > > 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? > > > > Well yeah something like this can be done, but what is the missing > > piece is where the IRQ domain actually gets created, i.e where this > > new version of platform_msi_create_device_domain() is called. That is > > the only piece that is currently done in the IOMMU driver only for DSA > > mdev. Not that all devices need to do it this way.. do you have > > suggestions as to where you want to call this function? > > Oops, I was thinking of platform_msi_domain_alloc_irqs() not > create_device_domain() > > ie call it in the device driver that wishes to consume the extra MSIs. > > Is there a harm if each device driver creates a new irq_domain for its use? Well, the only harm is if we want to reuse the irq domain. As of today, we only have DSA mdev which uses the dev-msi domain. In the IRQ domain hierarchy, We will have this: Vector-> intel-ir->dev-msi So tmrw if we have a new device, which would also want to have the intel-ir as the parent and use the same domain ops, we will simply be creating a copy of this IRQ domain, which may not be very fruitful. But apart from that, I don't think there are any issues.. What do you think is the best approach here? > > Jason
