Re: [PATCH v9 0/7] iommu/arm-smmu: Enable split pagetable support

Sai Prakash Ranjan
2020-07-01T10:12:52Z

Hi Will, Robin,

On 2020-06-27 01:30, Jordan Crouse wrote:
> Another iteration of the split-pagetable support for arm-smmu and the
> Adreno GPU
> SMMU. After email discussions [1] we opted to make a arm-smmu
> implementation for
> specifically for the Adreno GPU and use that to enable split pagetable
> support
> and later other implementation specific bits that we need.
>
> On the hardware side this is very close to the same code from before
> [2] only
> the TTBR1 quirk is turned on by the implementation and not a domain
> attribute.
> In drm/msm we use the returned size of the aperture as a clue to let us
> know
> which virtual address space we should use for global memory objects.
>
> There are two open items that you should be aware of. First, in the
> implementation specific code we have to check the compatible string of
> the
> device so that we only enable TTBR1 for the GPU (SID 0) and not the GMU
> (SID 4).
> I went back and forth trying to decide if I wanted to use the
> compatible string
> or the SID as the filter and settled on the compatible string but I
> could be
> talked out of it.
>
> The other open item is that in drm/msm the hardware only uses 49 bits
> of the
> address space but arm-smmu expects the address to be sign extended all
> the way
> to 64 bits. This isn't a problem normally unless you look at the
> hardware
> registers that contain a IOVA and then the upper bits will be zero. I
> opted to
> restrict the internal drm/msm IOVA range to only 49 bits and then sign
> extend
> right before calling iommu_map / iommu_unmap. This is a bit wonky but I
> thought
> that matching the hardware would be less confusing when debugging a
> hang.
>
> v9: Fix bot-detected merge conflict
> v7: Add attached device to smmu_domain to pass to implementation
> specific
> functions
>
> [1]
> https://lists.linuxfoundation.org/pipermail/iommu/2020-May/044537.html
> [2] https://patchwork.kernel.org/patch/11482591/
>
>
> Jordan Crouse (7):
> iommu/arm-smmu: Pass io-pgtable config to implementation specific
> function
> iommu/arm-smmu: Add support for split pagetables
> dt-bindings: arm-smmu: Add compatible string for Adreno GPU SMMU
> iommu/arm-smmu: Add a pointer to the attached device to smmu_domain
> iommu/arm-smmu: Add implementation for the adreno GPU SMMU
> drm/msm: Set the global virtual address range from the IOMMU domain
> arm: dts: qcom: sm845: Set the compatible string for the GPU SMMU
>
> .../devicetree/bindings/iommu/arm,smmu.yaml | 4 ++
> arch/arm64/boot/dts/qcom/sdm845.dtsi | 2 +-
> drivers/gpu/drm/msm/adreno/adreno_gpu.c | 13 +++++-
> drivers/gpu/drm/msm/msm_iommu.c | 7 +++
> drivers/iommu/arm-smmu-impl.c | 6 ++-
> drivers/iommu/arm-smmu-qcom.c | 45 ++++++++++++++++++-
> drivers/iommu/arm-smmu.c | 38 +++++++++++-----
> drivers/iommu/arm-smmu.h | 30 ++++++++++---
> 8 files changed, 120 insertions(+), 25 deletions(-)

Any chance reviewing this?

Thanks,
Sai

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