Re: [PATCH v2 0/8] Host1x context isolation support

Mikko Perttunen
2021-11-08T10:38:31Z

On 9/16/21 5:32 PM, Mikko Perttunen wrote:
> Hi all,
>
> ***
> New in v2:
>
> Added support for Tegra194
> Use standard iommu-map property instead of custom mechanism
> ***
>
> this series adds support for Host1x 'context isolation'. Since
> when programming engines through Host1x, userspace can program in
> any addresses it wants, we need some way to isolate the engines'
> memory spaces. Traditionally this has either been done imperfectly
> with a single shared IOMMU domain, or by copying and verifying the
> programming command stream at submit time (Host1x firewall).
>
> Since Tegra186 there is a privileged (only usable by kernel)
> Host1x opcode that allows setting the stream ID sent by the engine
> to the SMMU. So, by allocating a number of context banks and stream
> IDs for this purpose, and using this opcode at the beginning of
> each job, we can implement isolation. Due to the limited number of
> context banks only each process gets its own context, and not
> each channel.
>
> This feature also allows sharing engines among multiple VMs when
> used with Host1x's hardware virtualization support - up to 8 VMs
> can be configured with a subset of allowed stream IDs, enforced
> at hardware level.
>
> To implement this, this series adds a new host1x context bus, which
> will contain the 'struct device's corresponding to each context
> bank / stream ID, changes to device tree and SMMU code to allow
> registering the devices and using the bus, as well as the Host1x
> stream ID programming code and support in TegraDRM.
>
> Device tree bindings are not updated yet pending consensus that the
> proposed changes make sense.
>
> Thanks,
> Mikko
>
> Mikko Perttunen (8):
> gpu: host1x: Add context bus
> gpu: host1x: Add context device management code
> gpu: host1x: Program context stream ID on submission
> iommu/arm-smmu: Attach to host1x context device bus
> arm64: tegra: Add Host1x context stream IDs on Tegra186+
> drm/tegra: falcon: Set DMACTX field on DMA transactions
> drm/tegra: vic: Implement get_streamid_offset
> drm/tegra: Support context isolation
>
> arch/arm64/boot/dts/nvidia/tegra186.dtsi | 12 ++
> arch/arm64/boot/dts/nvidia/tegra194.dtsi | 12 ++
> drivers/gpu/Makefile | 3 +-
> drivers/gpu/drm/tegra/drm.h | 2 +
> drivers/gpu/drm/tegra/falcon.c | 8 +
> drivers/gpu/drm/tegra/falcon.h | 1 +
> drivers/gpu/drm/tegra/submit.c | 13 ++
> drivers/gpu/drm/tegra/uapi.c | 34 ++++-
> drivers/gpu/drm/tegra/vic.c | 38 +++++
> drivers/gpu/host1x/Kconfig | 5 +
> drivers/gpu/host1x/Makefile | 2 +
> drivers/gpu/host1x/context.c | 174 ++++++++++++++++++++++
> drivers/gpu/host1x/context.h | 27 ++++
> drivers/gpu/host1x/context_bus.c | 31 ++++
> drivers/gpu/host1x/dev.c | 12 +-
> drivers/gpu/host1x/dev.h | 2 +
> drivers/gpu/host1x/hw/channel_hw.c | 52 ++++++-
> drivers/gpu/host1x/hw/host1x06_hardware.h | 10 ++
> drivers/gpu/host1x/hw/host1x07_hardware.h | 10 ++
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 13 ++
> include/linux/host1x.h | 21 +++
> include/linux/host1x_context_bus.h | 15 ++
> 22 files changed, 488 insertions(+), 9 deletions(-)
> create mode 100644 drivers/gpu/host1x/context.c
> create mode 100644 drivers/gpu/host1x/context.h
> create mode 100644 drivers/gpu/host1x/context_bus.c
> create mode 100644 include/linux/host1x_context_bus.h
>

IOMMU/DT folks, any thoughts about this approach? The patches that are
of interest outside of Host1x/TegraDRM specifics are patches 1, 2, 4, and 5.

Thanks,
Mikko