RE: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Jason Wang <jasowang@redhat.com>
> Sent: Monday, September 14, 2020 12:20 PM
> 
> 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.
> 
> Jason suggest something like /dev/sva. There will be a lot of other
> subsystems that could benefit from this (e.g vDPA).
> 

Just be curious. When does vDPA subsystem plan to support vSVA and 
when could one expect a SVA-capable vDPA device in market?

Thanks
Kevin
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