RE: [PATCH v3 11/15] iommufd: Add a HW pagetable object

From: "Tian, Kevin" <kevin.tian@intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	David Woodhouse <dwmw2@infradead.org>,
	"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
	Joerg Roedel <joro@8bytes.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	"llvm@lists.linux.dev" <llvm@lists.linux.dev>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Miguel Ojeda <ojeda@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Shuah Khan <shuah@kernel.org>,
	Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	Tom Rix <trix@redhat.com>, Will Deacon <will@kernel.org>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	Chaitanya Kulkarni <chaitanyak@nvidia.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Daniel Jordan <daniel.m.jordan@oracle.com>,
	David Gibson <david@gibson.dropbear.id.au>,
	Eric Auger <eric.auger@redhat.com>,
	Eric Farman <farman@linux.ibm.com>,
	"Jason Wang" <jasowang@redhat.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	"Martins, Joao" <joao.m.martins@oracle.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Nicolin Chen <nicolinc@nvidia.com>,
	"Niklas Schnelle" <schnelle@linux.ibm.com>,
	Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	Keqian Zhu <zhukeqian1@huawei.com>
Subject: RE: [PATCH v3 11/15] iommufd: Add a HW pagetable object
Date: Fri, 4 Nov 2022 10:00:23 +0000	[thread overview]
Message-ID: <BN9PR11MB52762F734CF358C48FDFCB1C8C3B9@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <11-v3-402a7d6459de+24b-iommufd_jgg@nvidia.com>

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Wednesday, October 26, 2022 2:12 AM
> 
> The hw_pagetable object exposes the internal struct iommu_domain's to
> userspace. An iommu_domain is required when any DMA device attaches to
> an
> IOAS to control the io page table through the iommu driver.
> 
> For compatibility with VFIO the hw_pagetable is automatically created when
> a DMA device is attached to the IOAS. If a compatible iommu_domain
> already
> exists then the hw_pagetable associated with it is used for the
> attachment.
> 
> In the initial series there is no iommufd uAPI for the hw_pagetable
> object. The next patch provides driver facing APIs for IO page table
> attachment that allows drivers to accept either an IOAS or a hw_pagetable
> ID and for the driver to return the hw_pagetable ID that was auto-selected
> from an IOAS. The expectation is the driver will provide uAPI through its
> own FD for attaching its device to iommufd. This allows userspace to learn
> the mapping of devices to iommu_domains and to override the automatic
> attachment.
> 
> The future HW specific interface will allow userspace to create
> hw_pagetable objects using iommu_domains with IOMMU driver specific
> parameters. This infrastructure will allow linking those domains to IOAS's
> and devices.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>