Messages in this thread | | | From | "Dey, Megha" <> | Subject | RE: [PATCH RFC v2 02/18] irq/dev-msi: Add support for a new DEV_MSI irq domain | Date | Thu, 6 Aug 2020 00:32:31 +0000 |
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Hi Jason,
> -----Original Message----- > From: Jason Gunthorpe <jgg@mellanox.com> > Sent: Wednesday, August 5, 2020 5:19 PM > To: Dey, Megha <megha.dey@intel.com> > Cc: Marc Zyngier <maz@kernel.org>; Jiang, Dave <dave.jiang@intel.com>; > vkoul@kernel.org; bhelgaas@google.com; rafael@kernel.org; > gregkh@linuxfoundation.org; tglx@linutronix.de; hpa@zytor.com; > alex.williamson@redhat.com; Pan, Jacob jun <jacob.jun.pan@intel.com>; Raj, > Ashok <ashok.raj@intel.com>; Liu, Yi L <yi.l.liu@intel.com>; Lu, Baolu > <baolu.lu@intel.com>; Tian, Kevin <kevin.tian@intel.com>; Kumar, Sanjay K > <sanjay.k.kumar@intel.com>; Luck, Tony <tony.luck@intel.com>; Lin, Jing > <jing.lin@intel.com>; Williams, Dan J <dan.j.williams@intel.com>; > kwankhede@nvidia.com; eric.auger@redhat.com; parav@mellanox.com; > Hansen, Dave <dave.hansen@intel.com>; netanelg@mellanox.com; > shahafs@mellanox.com; yan.y.zhao@linux.intel.com; pbonzini@redhat.com; > Ortiz, Samuel <samuel.ortiz@intel.com>; Hossain, Mona > <mona.hossain@intel.com>; dmaengine@vger.kernel.org; linux- > kernel@vger.kernel.org; x86@kernel.org; linux-pci@vger.kernel.org; > kvm@vger.kernel.org > 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
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