Re: [PATCH RFC v1 00/15] iommu/virtio: Nested stage support with Arm

From: Vivek Kumar Gautam
Date: Thu Jan 21 2021 - 12:38:27 EST

Hi Eric,

On 1/19/21 2:33 PM, Auger Eric wrote:
Hi Vivek,

On 1/15/21 1:13 PM, Vivek Gautam wrote:
This patch-series aims at enabling Nested stage translation in guests
using virtio-iommu as the paravirtualized iommu. The backend is supported
with Arm SMMU-v3 that provides nested stage-1 and stage-2 translation.

This series derives its purpose from various efforts happening to add
support for Shared Virtual Addressing (SVA) in host and guest. On Arm,
most of the support for SVA has already landed. The support for nested
stage translation and fault reporting to guest has been proposed [1].
The related changes required in VFIO [2] framework have also been put

This series proposes changes in virtio-iommu to program PASID tables
and related stage-1 page tables. A simple iommu-pasid-table library
is added for this purpose that interacts with vendor drivers to
allocate and populate PASID tables.
In Arm SMMUv3 we propose to pull the Context Descriptor (CD) management
code out of the arm-smmu-v3 driver and add that as a glue vendor layer
to support allocating CD tables, and populating them with right values.
These CD tables are essentially the PASID tables and contain stage-1
page table configurations too.
A request to setup these CD tables come from virtio-iommu driver using
the iommu-pasid-table library when running on Arm. The virtio-iommu
then pass these PASID tables to the host using the right virtio backend
and support in VMM.

For testing we have added necessary support in kvmtool. The changes in
kvmtool are based on virtio-iommu development branch by Jean-Philippe
Brucker [3].

The tested kernel branch contains following in the order bottom to top
on the git hash -
a) v5.11-rc3
b) arm-smmu-v3 [1] and vfio [2] changes from Eric to add nested page
table support for Arm.
c) Smmu test engine patches from Jean-Philippe's branch [4]
d) This series
e) Domain nesting info patches [5][6][7].
f) Changes to add arm-smmu-v3 specific nesting info (to be sent to
the list).

This kernel is tested on Neoverse reference software stack with
Fixed virtual platform. Public version of the software stack and
FVP is available here[8][9].

A big thanks to Jean-Philippe for his contributions towards this work
and for his valuable guidance.


Could you share a public branch where we could find all the kernel pieces.

Thank you in advance

Apologies for the delay. It took a bit of time to sort things out for a public branch.
The branch is available in my github now. Please have a look.

Thanks and regards

Best Regards


Jean-Philippe Brucker (6):
iommu/virtio: Add headers for table format probing
iommu/virtio: Add table format probing
iommu/virtio: Add headers for binding pasid table in iommu
iommu/virtio: Add support for INVALIDATE request
iommu/virtio: Attach Arm PASID tables when available
iommu/virtio: Add support for Arm LPAE page table format

Vivek Gautam (9):
iommu/arm-smmu-v3: Create a Context Descriptor library
iommu: Add a simple PASID table library
iommu/arm-smmu-v3: Update drivers to work with iommu-pasid-table
iommu/arm-smmu-v3: Update CD base address info for user-space
iommu/arm-smmu-v3: Set sync op from consumer driver of cd-lib
iommu: Add asid_bits to arm smmu-v3 stage1 table info
iommu/virtio: Update table format probing header
iommu/virtio: Prepare to add attach pasid table infrastructure
iommu/virtio: Update fault type and reason info for viommu fault

drivers/iommu/arm/arm-smmu-v3/Makefile | 2 +-
.../arm/arm-smmu-v3/arm-smmu-v3-cd-lib.c | 283 +++++++
.../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 16 +-
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 268 +------
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 4 +-
drivers/iommu/iommu-pasid-table.h | 140 ++++
drivers/iommu/virtio-iommu.c | 692 +++++++++++++++++-
include/uapi/linux/iommu.h | 2 +-
include/uapi/linux/virtio_iommu.h | 158 +++-
9 files changed, 1303 insertions(+), 262 deletions(-)
create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-cd-lib.c
create mode 100644 drivers/iommu/iommu-pasid-table.h