Re: [RFC v10 00/25] intel_iommu: expose Shared Virtual Addressing to VMs

[Zenghui Yu]

Hi Yi,

On 2020/9/10 18:56, Liu Yi L wrote:
> 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|
>      |             |   '------------------------------'
>      '-------------'

A silly question: With nested mode, do we need to setup the second level
mappings (GPA->HPA) for devices before vm startup? If so, can you please
point me to the piece of code that achieves it?

On Arm, we setup the stage-2 mapping via the new prereg_listener [1].

[1] 
20210225105233.650545-15-eric.auger@redhat.com/">https://patchwork.kernel.org/project/qemu-devel/patch/20210225105233.650545-15-eric.auger@redhat.com/


Thanks,
Zenghui