Re: [PATCH v7 03/10] iommu/sva: Add iommu_sva_domain support

From: Jason Gunthorpe via iommu <iommu@lists.linux-foundation.org>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
	"Jiang, Dave" <dave.jiang@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	Vinod Koul <vkoul@kernel.org>,
	"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v7 03/10] iommu/sva: Add iommu_sva_domain support
Date: Tue, 24 May 2022 10:38:39 -0300	[thread overview]
Message-ID: <20220524133839.GS1343366@nvidia.com> (raw)
In-Reply-To: <BN9PR11MB5276982C37DFF0FEFC45BDD68CD79@BN9PR11MB5276.namprd11.prod.outlook.com>

On Tue, May 24, 2022 at 09:39:52AM +0000, Tian, Kevin wrote:
> > From: Lu Baolu <baolu.lu@linux.intel.com>
> > Sent: Thursday, May 19, 2022 3:21 PM
> > 
> > The iommu_sva_domain represents a hardware pagetable that the IOMMU
> > hardware could use for SVA translation. This adds some infrastructure
> > to support SVA domain in the iommu common layer. It includes:
> > 
> > - Add a new struct iommu_sva_domain and new IOMMU_DOMAIN_SVA
> > domain
> >   type.
> > - Add a new domain ops pointer in iommu_ops. The IOMMU drivers that
> >   support SVA should provide the callbacks.
> > - Add helpers to allocate and free an SVA domain.
> > - Add helpers to set an SVA domain to a device and the reverse
> >   operation.
> > 
> > Some buses, like PCI, route packets without considering the PASID value.
> > Thus a DMA target address with PASID might be treated as P2P if the
> > address falls into the MMIO BAR of other devices in the group. To make
> > things simple, the attach/detach interfaces only apply to devices
> > belonging to the singleton groups, and the singleton is immutable in
> > fabric i.e. not affected by hotplug.
> > 
> > The iommu_set/block_device_pasid() can be used for other purposes,
> > such as kernel DMA with pasid, mediation device, etc. Hence, it is put
> > in the iommu.c.
> 
> usually we have 'set/clear' pair or 'allow/block'. Having 'set' paired
> with 'block' doesn't read very clearly.

I thought we agreed we'd use the blocking domain for this? Why did it
go back to an op?

Jason
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