On an ARM64 system with a SMMUv3 implementation that fully supports Broadcast TLB Maintenance(BTM) feature as part of the Distributed Virtual Memory(DVM) protocol, the CPU TLB invalidate instructions are received by SMMUv3. This is very useful when the SMMUv3 shares the page tables with the CPU(eg: Guest SVA use case). For this to work, the SMMU must use the same VMID that is allocated by KVM to configure the stage 2 translations. At present KVM VMID allocations are recycled on rollover and may change as a result. This will create issues if we have to share the KVM VMID with SMMU. Please see the discussion here, https://lore.kernel.org/linux-iommu/20200522101755.GA3453945@myrica/ This series proposes a way to share the VMID between KVM and IOMMU driver by, 1. Splitting the KVM VMID space into two equal halves based on the command line option "kvm-arm.pinned_vmid_enable". 2. First half of the VMID space follows the normal recycle on rollover policy. 3. Second half of the VMID space doesn't roll over and is used to allocate pinned VMIDs. 4. Provides helper function to retrieve the KVM instance associated with a device(if it is part of a vfio group). 5. Introduces generic interfaces to get/put pinned KVM VMIDs. Open Items: 1. I couldn't figure out a way to determine whether a platform actually fully supports DVM/BTM or not. Not sure we can take a call based on SMMUv3 BTM feature bit alone. Probably we can get it from firmware via IORT? 2. The current splitting of VMID space is only one way to do this and probably not the best. Maybe we can follow the pinned ASID method used in SVA code. Suggestions welcome here. 3. The detach_pasid_table() interface is not very clear to me as the current Qemu prototype is not using that. This requires fixing from my side. This is based on Jean-Philippe's SVA series[1] and Eric's SMMUv3 dual-stage support series[2]. The branch with the whole vSVA + BTM solution is here, https://github.com/hisilicon/kernel-dev/tree/5.10-rc4-2stage-v13-vsva-btm-rfc This is lightly tested on a HiSilicon D06 platform with uacce/zip dev test tool, ./zip_sva_per -k tlb Thanks, Shameer 1. https://github.com/Linaro/linux-kernel-uadk/commits/uacce-devel-5.10 2. https://lore.kernel.org/linux-iommu/20201118112151.25412-1-eric.auger@xxxxxxxxxx/T/ Shameer Kolothum (5): vfio: Add a helper to retrieve kvm instance from a dev KVM: Add generic infrastructure to support pinned VMIDs KVM: ARM64: Add support for pinned VMIDs iommu/arm-smmu-v3: Use pinned VMID for NESTED stage with BTM KVM: arm64: Make sure pinned vmid is released on VM exit arch/arm64/include/asm/kvm_host.h | 2 + arch/arm64/kvm/Kconfig | 1 + arch/arm64/kvm/arm.c | 116 +++++++++++++++++++- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 49 ++++++++- drivers/vfio/vfio.c | 12 ++ include/linux/kvm_host.h | 17 +++ include/linux/vfio.h | 1 + virt/kvm/Kconfig | 2 + virt/kvm/kvm_main.c | 25 +++++ 9 files changed, 220 insertions(+), 5 deletions(-) -- 2.17.1 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
