linux-kernel - Re: [PATCH v2 0/6] IOMMUFD: Deliver IO page faults to user space

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Date:   Mon, 4 Dec 2023 16:07:44 +0100
From:   Joel Granados <j.granados@...sung.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
CC:     Jason Gunthorpe <jgg@...pe.ca>, Kevin Tian <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        <iommu@...ts.linux.dev>, <linux-kselftest@...r.kernel.org>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/6] IOMMUFD: Deliver IO page faults to user space

On Thu, Oct 26, 2023 at 10:49:24AM +0800, Lu Baolu wrote:
> Hi folks,
> 
> This series implements the functionality of delivering IO page faults to
> user space through the IOMMUFD framework for nested translation. Nested
Does this mean the IOPF_CAPABLE HWPT needs to be parented by a HWPT
created with IOMMU_HWPT_ALLOC_NEST_PARENT set?

> translation is a hardware feature that supports two-stage translation
> tables for IOMMU. The second-stage translation table is managed by the
> host VMM, while the first-stage translation table is owned by user
> space. This allows user space to control the IOMMU mappings for its
> devices.
> 
> When an IO page fault occurs on the first-stage translation table, the
> IOMMU hardware can deliver the page fault to user space through the
> IOMMUFD framework. User space can then handle the page fault and respond
> to the device top-down through the IOMMUFD. This allows user space to
> implement its own IO page fault handling policies.
> 
> User space indicates its capability of handling IO page faults by
> setting the IOMMU_HWPT_ALLOC_IOPF_CAPABLE flag when allocating a
> hardware page table (HWPT). IOMMUFD will then set up its infrastructure
> for page fault delivery. On a successful return of HWPT allocation, the
> user can retrieve and respond to page faults by reading and writing to
> the file descriptor (FD) returned in out_fault_fd.
> 
> The iommu selftest framework has been updated to test the IO page fault
> delivery and response functionality.
> 
> This series is based on the latest implementation of nested translation
> under discussion [1] and the page fault handling framework refactoring in
> the IOMMU core [2].
> 
> The series and related patches are available on GitHub: [3]
> 
> [1] https://lore.kernel.org/linux-iommu/20230921075138.124099-1-yi.l.liu@intel.com/
> [2] https://lore.kernel.org/linux-iommu/20230928042734.16134-1-baolu.lu@linux.intel.com/
> [3] https://github.com/LuBaolu/intel-iommu/commits/iommufd-io-pgfault-delivery-v2
> 
> Best regards,
> baolu
> 
> Change log:
> v2:
>  - Move all iommu refactoring patches into a sparated series and discuss
>    it in a different thread. The latest patch series [v6] is available at
>    https://lore.kernel.org/linux-iommu/20230928042734.16134-1-baolu.lu@linux.intel.com/
>  - We discussed the timeout of the pending page fault messages. We
>    agreed that we shouldn't apply any timeout policy for the page fault
>    handling in user space.
>    https://lore.kernel.org/linux-iommu/20230616113232.GA84678@myrica/
>  - Jason suggested that we adopt a simple file descriptor interface for
>    reading and responding to I/O page requests, so that user space
>    applications can improve performance using io_uring.
>    https://lore.kernel.org/linux-iommu/ZJWjD1ajeem6pK3I@ziepe.ca/
> 
> v1: https://lore.kernel.org/linux-iommu/20230530053724.232765-1-baolu.lu@linux.intel.com/
> 
> Lu Baolu (6):
>   iommu: Add iommu page fault cookie helpers
>   iommufd: Add iommu page fault uapi data
>   iommufd: Initializing and releasing IO page fault data
>   iommufd: Deliver fault messages to user space
>   iommufd/selftest: Add IOMMU_TEST_OP_TRIGGER_IOPF test support
>   iommufd/selftest: Add coverage for IOMMU_TEST_OP_TRIGGER_IOPF
> 
>  include/linux/iommu.h                         |   9 +
>  drivers/iommu/iommu-priv.h                    |  15 +
>  drivers/iommu/iommufd/iommufd_private.h       |  12 +
>  drivers/iommu/iommufd/iommufd_test.h          |   8 +
>  include/uapi/linux/iommufd.h                  |  65 +++++
>  tools/testing/selftests/iommu/iommufd_utils.h |  66 ++++-
>  drivers/iommu/io-pgfault.c                    |  50 ++++
>  drivers/iommu/iommufd/device.c                |  69 ++++-
>  drivers/iommu/iommufd/hw_pagetable.c          | 260 +++++++++++++++++-
>  drivers/iommu/iommufd/selftest.c              |  56 ++++
>  tools/testing/selftests/iommu/iommufd.c       |  24 +-
>  .../selftests/iommu/iommufd_fail_nth.c        |   2 +-
>  12 files changed, 620 insertions(+), 16 deletions(-)
> 
> -- 
> 2.34.1
> 

-- 

Joel Granados

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