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/by5pr12mb37641e84d516054387fee330b3...@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-phili...@linaro.org/ [4] https://lore.kernel.org/linux-pci/1610960316-28935-1-git-send-email-zhangfei....@linaro.org/ 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(-) -- 2.30.0 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
