On Mon, Sep 14, 2020 at 12:20:10PM +0800, Jason Wang wrote: > > On 2020/9/10 下午6:45, Liu Yi L wrote: > > Shared Virtual Addressing (SVA), a.k.a, Shared Virtual Memory (SVM) on > > Intel platforms allows address space sharing between device DMA and > > applications. SVA can reduce programming complexity and enhance security. > > > > This VFIO series is intended to expose SVA usage to VMs. i.e. Sharing > > guest application address space with passthru devices. This is called > > vSVA in this series. The whole vSVA enabling requires QEMU/VFIO/IOMMU > > changes. For IOMMU and QEMU changes, they are in separate series (listed > > in the "Related series"). > > > > The high-level architecture for SVA virtualization is as below, the key > > design of vSVA support is to utilize the dual-stage IOMMU translation ( > > also known as IOMMU nesting translation) capability in host IOMMU. > > > > > > .-------------. .---------------------------. > > | vIOMMU | | Guest process CR3, FL only| > > | | '---------------------------' > > .----------------/ > > | PASID Entry |--- PASID cache flush - > > '-------------' | > > | | V > > | | CR3 in GPA > > '-------------' > > Guest > > ------| Shadow |--------------------------|-------- > > v v v > > Host > > .-------------. .----------------------. > > | pIOMMU | | Bind FL for GVA-GPA | > > | | '----------------------' > > .----------------/ | > > | PASID Entry | V (Nested xlate) > > '----------------\.------------------------------. > > | ||SL for GPA-HPA, default domain| > > | | '------------------------------' > > '-------------' > > Where: > > - FL = First level/stage one page tables > > - SL = Second level/stage two page tables > > > > Patch Overview: > > 1. reports IOMMU nesting info to userspace ( patch 0001, 0002, 0003, 0015 , 0016) > > 2. vfio support for PASID allocation and free for VMs (patch 0004, 0005, 0007) > > 3. a fix to a revisit in intel iommu driver (patch 0006) > > 4. vfio support for binding guest page table to host (patch 0008, 0009, 0010) > > 5. vfio support for IOMMU cache invalidation from VMs (patch 0011) > > 6. vfio support for vSVA usage on IOMMU-backed mdevs (patch 0012) > > 7. expose PASID capability to VM (patch 0013) > > 8. add doc for VFIO dual stage control (patch 0014) > > > If it's possible, I would suggest a generic uAPI instead of a VFIO specific > one. A large part of this work is already generic uAPI, in include/uapi/linux/iommu.h. This patchset connects that generic interface to the pre-existing VFIO uAPI that deals with IOMMU mappings of an assigned device. But the bulk of the work is done by the IOMMU subsystem, and is available to all device drivers. > Jason suggest something like /dev/sva. There will be a lot of other > subsystems that could benefit from this (e.g vDPA). Do you have a more precise idea of the interface /dev/sva would provide, how it would interact with VFIO and others? vDPA could transport the generic iommu.h structures via its own uAPI, and call the IOMMU API directly without going through an intermediate /dev/sva handle. Thanks, Jean > Have you ever considered this approach? > > Thanks >
