From: Jason Gunthorpe <jgg@nvidia.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Arnd Bergmann <arnd@arndb.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Marc Zyngier <maz@kernel.org>, Oliver Upton <oupton@kernel.org>,
Alex Williamson <alex@shazbot.org>, Rob Herring <robh@kernel.org>,
Krzysztof Kozlowski <krzk+dt@kernel.org>,
Conor Dooley <conor+dt@kernel.org>,
Jean-Philippe Brucker <jpb@kernel.org>,
Oded Gabbay <ogabbay@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
kvm@vger.kernel.org, devicetree@vger.kernel.org,
dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org
Subject: Re: [RFC PATCH v2 12/15] vfio: Support VFIO devices that access the CPU MMU
Date: Thu, 15 Oct 2026 13:44:21 -0300 [thread overview]
Message-ID: <20261015164421.GD13920@nvidia.com> (raw)
In-Reply-To: <20261015142552.4128028-13-ryan.roberts@arm.com>
On Thu, Oct 15, 2026 at 03:25:46PM +0100, Ryan Roberts wrote:
> From: Jean-Philippe Brucker <jpb@kernel.org>
>
> Support devices that are attached to a CPU and perform DMA through a
> MMU. They do not have an IOMMU and do not use a VFIO container.
> The VMM needs device-specific knowledge in order to create a virtual
> device (device tree, ACPI tables), so it also knows not to allocate a
> container.
I'm not so excited to see new things built on top of the group
interface.
Maybe in this case you just don't have to do a bind operation on the
cdev to an iommufd? That feels kind of natural if you don't use a
iommufd
However.. you still have to affirm which single mm is the mm that the
device is going to be doing DMA against. The process the opens the fd
should not be forced to be the mm that it gets linked to.
From that perspective maybe you should create an iommufd and a special
"SVA" IOAS that it can attach to. This is more complicated but it
makes the mm linkage and blocking beahvior explicit and controlled by
userspace.
Jason
next prev parent reply other threads:[~2026-10-15 16:44 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 14:25 [RFC PATCH v2 00/15] Arm Core Local Accelerator Driver Ryan Roberts
2026-10-15 14:25 ` [RFC PATCH v2 01/15] misc/arm-cla: Add driver skeleton and documentation Ryan Roberts
2026-10-15 14:35 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 02/15] misc/arm-cla: Add launch operation helpers Ryan Roberts
2026-10-15 14:42 ` sashiko-bot
2026-10-15 16:17 ` Greg Kroah-Hartman
2026-10-15 16:32 ` Ryan Roberts
2026-10-15 14:25 ` [RFC PATCH v2 03/15] dt-bindings: misc: Add Arm Core Local Accelerator Ryan Roberts
2026-10-15 14:25 ` [RFC PATCH v2 04/15] misc/arm-cla: Probe firmware-described devices Ryan Roberts
2026-10-15 14:37 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 05/15] misc/arm-cla: Initialize devices on CPU bringup Ryan Roberts
2026-10-15 14:25 ` [RFC PATCH v2 06/15] misc/arm-cla: Accelerator context save and restore Ryan Roberts
2026-10-15 14:41 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 07/15] misc/arm-cla: Set up memory translation context Ryan Roberts
2026-10-15 14:25 ` [RFC PATCH v2 08/15] misc/arm-cla: Manage domain contexts Ryan Roberts
2026-10-15 14:38 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 09/15] misc/arm-cla: Add userspace interface Ryan Roberts
2026-10-15 14:47 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 10/15] KVM: arm64: Introduce support to pin VMIDs Ryan Roberts
2026-10-15 14:38 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 11/15] KVM: arm64: Export stage-2 MMU config Ryan Roberts
2026-10-15 14:43 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 12/15] vfio: Support VFIO devices that access the CPU MMU Ryan Roberts
2026-10-15 14:44 ` sashiko-bot
2026-10-15 16:44 ` Jason Gunthorpe [this message]
2026-10-15 14:25 ` [RFC PATCH v2 13/15] misc/arm-cla: Add stage-2 MTC and VM context switch Ryan Roberts
2026-10-15 14:40 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 14/15] misc/arm-cla: Support exclusive context assignment Ryan Roberts
2026-10-15 14:41 ` sashiko-bot
2026-10-15 14:25 ` [RFC PATCH v2 15/15] misc/arm-cla: Add vfio-mdev user interface Ryan Roberts
2026-10-15 14:49 ` sashiko-bot
2026-10-15 16:41 ` Jason Gunthorpe
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