Re: [PATCH 0/3] iommu/arm-smmu-v3: TLB invalidation for SVA

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Fri, 22 Jan 2021 12:52:55 +0100
Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:

> To support sharing page tables with the CPU, the SMMU can participate in
> Broadcast TLB Maintenance (BTM), where TLB invalidate instructions from
> the CPU are received by the SMMU. For platforms that do no implement BTM
> [1], it is still possible to use SVA, by sending all TLB invalidations
> through the command queue. Patch 2 implements this.
> 
> This series also enables SVA for platforms that do support BTM, as an
> intermediate step because properly supporting BTM requires cooperating
> with KVM to allocate VMIDs [2]. With BTM enabled, the SMMU applies
> broadcast invalidations by VMID to any matching TLB entry, because there
> is no distinction between private and shared VMIDs like there is for
> ASIDs. Therefore a stage-2 domain will need a VMID that doesn't conflict
> with one allocated by KVM (or use the one from the corresponding VM,
> pinned).
> 
> These patches, along with the IOPF series [3] and the quirks [4], enable
> SVA for the hisi accelerator that's already supported upstream. My quick
> performance comparison between BTM and !BTM on that platform were
> inconclusive. Doing invalidations via cmdq seemed to slightly reduce
> performance of some heavy compression jobs, but there was too much noise
> and not enough invalidations in my tests.
> 
> This series does not depend on the IOPF one [3].
> 
> [1] https://lore.kernel.org/linux-iommu/BY5PR12MB37641E84D516054387FEE330B3CC0@BY5PR12MB3764.namprd12.prod.outlook.com/
> [2] https://lore.kernel.org/linux-iommu/20200522101755.GA3453945@myrica/
> [3] https://lore.kernel.org/linux-iommu/20210121123623.2060416-1-jean-philippe@linaro.org/
> [4] https://lore.kernel.org/linux-pci/1610960316-28935-1-git-send-email-zhangfei.gao@linaro.org/

Whole series looks good to me so FWIW
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Will be very nice to have mainline support for SVA with those accelerators :)

> 
> Jean-Philippe Brucker (3):
>   iommu/arm-smmu-v3: Split arm_smmu_tlb_inv_range()
>   iommu/arm-smmu-v3: Make BTM optional for SVA
>   iommu/arm-smmu-v3: Add support for VHE
> 
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |   6 +
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   |  14 ++-
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 104 ++++++++++++------
>  3 files changed, 89 insertions(+), 35 deletions(-)
> 


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