From: Nicolin Chen <nicolinc@nvidia.com>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
Cc: <iommu@lists.linux.dev>, Alex Williamson <alex@shazbot.org>,
"Alexey Kardashevskiy" <aik@amd.com>,
Bjorn Helgaas <bhelgaas@google.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
Jacob Pan <jacob.pan@linux.microsoft.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Joerg Roedel <joro@8bytes.org>,
"Jonathan Cameron" <jic23@kernel.org>,
Jonathan Hunter <jonathanh@nvidia.com>,
"Kevin Tian" <kevin.tian@intel.com>,
Krishna Reddy <vdumpa@nvidia.com>, Lukas Wunner <lukas@wunner.de>,
Robin Murphy <robin.murphy@arm.com>,
Samuel Ortiz <sameo@rivosinc.com>,
Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
Steven Price <steven.price@arm.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Thierry Reding <thierry.reding@kernel.org>,
"Vasant Hegde" <vasant.hegde@amd.com>,
Will Deacon <will@kernel.org>,
Xu Yilun <yilun.xu@linux.intel.com>, <kvm@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-coco@lists.linux.dev>, <linux-kernel@vger.kernel.org>,
<linux-pci@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH v8 13/15] iommufd/viommu: Allow vIOMMUs without a parent HWPT
Date: Wed, 4 Nov 2026 11:03:41 -0800 [thread overview]
Message-ID: <auuBjRjQwXl7UvvO@nvidia.com> (raw)
In-Reply-To: <20261104161632.3547423-14-aneesh.kumar@kernel.org>
On Wed, Nov 04, 2026 at 09:46:30PM +0530, Aneesh Kumar K.V (Arm) wrote:
> VIOMMU_ALLOC currently requires a nesting parent HWPT_PAGING even when
> the selected vIOMMU implementation has no use for one. This would force
> implementations such as the following Arm Realm vIOMMU to create an
> unused parent.
IIRC, MSI on ARM still goes through the NS pathway. So, it wouldn't
be "unused" if the device attaches to it (or its nested hwpts)?
By dropping the nesting parent from VIOMMU, it just simplifies the
attachment to an S1 paging hwpt, right?
Nicolin
next prev parent reply other threads:[~2026-11-04 19:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-04 16:16 [PATCH v8 00/15] iommufd: TSM-backed virtual IOMMUs for confidential guests Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 01/15] PCI/TSM: Move core code into its own directory Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 02/15] virt: coco: tsm: Remove the device from lookup before PCI teardown Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 03/15] virt: coco: tsm: Complete PCI registration before publishing the device Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 04/15] virt: coco: tsm: Require PCI operations when registering a TSM Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 05/15] iommufd/device: Associate KVM file pointer with iommufd_device Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 06/15] iommufd/device: Hold a KVM file reference for the device lifetime Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 07/15] iommufd/viommu: Keep a reference to the KVM file Aneesh Kumar K.V (Arm)
2026-11-04 16:35 ` Jacob Pan
2026-11-04 16:16 ` [PATCH v8 08/15] iommufd: Add a vDEVICE operation ioctl framework Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 09/15] PCI/TSM: Remove the legacy guest request interface Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 10/15] PCI/TSM: Add vIOMMU-bound device contexts Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 11/15] iommufd/viommu: Select vIOMMU operations before allocation Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 12/15] iommufd/viommu: Allow PCI TSM backends to provide vIOMMU operations Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 13/15] iommufd/viommu: Allow vIOMMUs without a parent HWPT Aneesh Kumar K.V (Arm)
2026-11-04 19:03 ` Nicolin Chen [this message]
2026-11-04 19:31 ` Jason Gunthorpe
2026-11-04 16:16 ` [PATCH v8 14/15] PCI/TSM: Wait for device contexts before removing a DSM Aneesh Kumar K.V (Arm)
2026-11-04 16:16 ` [PATCH v8 15/15] PCI/TSM: Wait for users during unregister Aneesh Kumar K.V (Arm)
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