[PATCH v15 0/3] iommu/arm-smmu-v3: Add stall support

[Jean-Philippe Brucker]

Add stall support for SMMUv3, enabling I/O page faults and SVA for
compatible devices. No change since last version [1], but I'd still like
this to be considered for upstream, because there exists hardware and
applications.

Stall is implemented by the Kunpeng 920 processor for its compression
and crypto accelerators, with which I tested the SVA infrastructure.
Using the userspace accelerator API [2], a program can obtain a queue
from one of these devices and submit compression or encryption work
within the program's address space. UADK [3] provides a library to do
this, and there is an openssl plugin [4] to use it.

That's probably as far as we can go in terms of real users of SVA at the
moment, since userspace won't progress much further without upstream
kernel support - these three patches.

Stall is only enabled if the firmware declares that the device supports
stalling (explicit flags from patches 1 and 2) or, in the case of the
Kunpeng 920, with a quirk [5]. If that property is not set, stall will
still be disabled in the STE and CD, and this series should not have any
negative impact on existing systems.

[1] https://lore.kernel.org/linux-iommu/20210401154718.307519-1-jean-philippe@linaro.org/
[2] Documentation/misc-devices/uacce.rst
[3] https://github.com/Linaro/uadk
[4] https://github.com/Linaro/openssl-uadk
[5] https://lore.kernel.org/linux-pci/1615258837-12189-1-git-send-email-zhangfei.gao@linaro.org/
    FWIW future devices should implement PRI:
    https://lore.kernel.org/linux-pci/5FD9EE6E.1040505@hisilicon.com/

Jean-Philippe Brucker (3):
  dt-bindings: document stall property for IOMMU masters
  ACPI/IORT: Enable stall support for platform devices
  iommu/arm-smmu-v3: Add stall support for platform devices

 .../devicetree/bindings/iommu/iommu.txt       |  18 ++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  43 ++++
 drivers/acpi/arm64/iort.c                     |   4 +-
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   |  59 +++++-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 196 +++++++++++++++++-
 5 files changed, 304 insertions(+), 16 deletions(-)

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2.31.1