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

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Message-ID: <10de82cf-27a5-8890-93a5-0e58c74e5bcc@kapsi.fi>
Date:   Mon, 8 Nov 2021 12:36:51 +0200
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Mikko Perttunen <mperttunen@...dia.com>, thierry.reding@...il.com,
        jonathanh@...dia.com, joro@...tes.org, will@...nel.org,
        robh+dt@...nel.org, robin.murphy@....com
Cc:     linux-tegra@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 0/8] Host1x context isolation support

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