RE: [RFC v2 00/22] intel_iommu: expose Shared Virtual Addressing to VM

[Tian, Kevin]

> From: Jason Wang [mailto:address@hidden]
> Sent: Friday, October 25, 2019 5:49 PM
> 
> 
> On 2019/10/24 下午8:34, Liu Yi L wrote:
> > Shared virtual address (SVA), a.k.a, Shared virtual memory (SVM) on Intel
> > platforms allow address space sharing between device DMA and
> applications.
> 
> 
> Interesting, so the below figure demonstrates the case of VM. I wonder
> how much differences if we compare it with doing SVM between device
> and
> an ordinary process (e.g dpdk)?
> 
> Thanks

One difference is that ordinary process requires only stage-1 translation,
while VM requires nested translation.

> 
> 
> > SVA can reduce programming complexity and enhance security.
> > This series is intended to expose SVA capability to VMs. i.e. shared guest
> > application address space with passthru devices. The whole SVA
> virtualization
> > requires QEMU/VFIO/IOMMU changes. This series includes the QEMU
> changes, for
> > VFIO and IOMMU changes, they are in separate series (listed in the
> "Related
> > series").
> >
> > The high-level architecture for SVA virtualization is as below:
> >
> >      .-------------.  .---------------------------.
> >      |   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
> >
> > The complete vSVA upstream patches are divided into three phases:
> >      1. Common APIs and PCI device direct assignment
> >      2. Page Request Services (PRS) support
> >      3. Mediated device assignment
> >
> > This RFC patchset is aiming for the phase 1. Works together with the VT-d
> > driver[1] changes and VFIO changes[2].
> >
> > Related series:
> > [1] [PATCH v6 00/10] Nested Shared Virtual Address (SVA) VT-d support:
> > https://lkml.org/lkml/2019/10/22/953
> > <This series is based on this kernel series from Jacob Pan>
> >
> > [2] [RFC v2 0/3] vfio: support Shared Virtual Addressing from Yi Liu
> >
> > There are roughly four parts:
> >   1. Introduce IOMMUContext as abstract layer between vIOMMU
> emulator and
> >      VFIO to avoid direct calling between the two
> >   2. Passdown PASID allocation and free to host
> >   3. Passdown guest PASID binding to host
> >   4. Passdown guest IOMMU cache invalidation to host
> >
> > The full set can be found in below link:
> > https://github.com/luxis1999/qemu.git: sva_vtd_v6_qemu_rfc_v2
> >
> > Changelog:
> >     - RFC v1 -> v2:
> >       Introduce IOMMUContext to abstract the connection between
> VFIO
> >       and vIOMMU emulator, which is a replacement of the
> PCIPASIDOps
> >       in RFC v1. Modify x-scalable-mode to be string option instead of
> >       adding a new option as RFC v1 did. Refined the pasid cache
> management
> >       and addressed the TODOs mentioned in RFC v1.
> >       RFC v1: https://patchwork.kernel.org/cover/11033657/
> >
> > Eric Auger (1):
> >    update-linux-headers: Import iommu.h
> >
> > Liu Yi L (20):
> >    header update VFIO/IOMMU vSVA APIs against 5.4.0-rc3+
> >    intel_iommu: modify x-scalable-mode to be string option
> >    vfio/common: add iommu_ctx_notifier in container
> >    hw/pci: modify pci_setup_iommu() to set PCIIOMMUOps
> >    hw/pci: introduce pci_device_iommu_context()
> >    intel_iommu: provide get_iommu_context() callback
> >    vfio/pci: add iommu_context notifier for pasid alloc/free
> >    intel_iommu: add virtual command capability support
> >    intel_iommu: process pasid cache invalidation
> >    intel_iommu: add present bit check for pasid table entries
> >    intel_iommu: add PASID cache management infrastructure
> >    vfio/pci: add iommu_context notifier for pasid bind/unbind
> >    intel_iommu: bind/unbind guest page table to host
> >    intel_iommu: replay guest pasid bindings to host
> >    intel_iommu: replay pasid binds after context cache invalidation
> >    intel_iommu: do not passdown pasid bind for PASID #0
> >    vfio/pci: add iommu_context notifier for PASID-based iotlb flush
> >    intel_iommu: process PASID-based iotlb invalidation
> >    intel_iommu: propagate PASID-based iotlb invalidation to host
> >    intel_iommu: process PASID-based Device-TLB invalidation
> >
> > Peter Xu (1):
> >    hw/iommu: introduce IOMMUContext
> >
> >   hw/Makefile.objs                |    1 +
> >   hw/alpha/typhoon.c              |    6 +-
> >   hw/arm/smmu-common.c            |    6 +-
> >   hw/hppa/dino.c                  |    6 +-
> >   hw/i386/amd_iommu.c             |    6 +-
> >   hw/i386/intel_iommu.c           | 1249
> +++++++++++++++++++++++++++++++++++++--
> >   hw/i386/intel_iommu_internal.h  |  109 ++++
> >   hw/i386/trace-events            |    6 +
> >   hw/iommu/Makefile.objs          |    1 +
> >   hw/iommu/iommu.c                |   66 +++
> >   hw/pci-host/designware.c        |    6 +-
> >   hw/pci-host/ppce500.c           |    6 +-
> >   hw/pci-host/prep.c              |    6 +-
> >   hw/pci-host/sabre.c             |    6 +-
> >   hw/pci/pci.c                    |   27 +-
> >   hw/ppc/ppc440_pcix.c            |    6 +-
> >   hw/ppc/spapr_pci.c              |    6 +-
> >   hw/s390x/s390-pci-bus.c         |    8 +-
> >   hw/vfio/common.c                |   10 +
> >   hw/vfio/pci.c                   |  149 +++++
> >   include/hw/i386/intel_iommu.h   |   58 +-
> >   include/hw/iommu/iommu.h        |  113 ++++
> >   include/hw/pci/pci.h            |   13 +-
> >   include/hw/pci/pci_bus.h        |    2 +-
> >   include/hw/vfio/vfio-common.h   |    9 +
> >   linux-headers/linux/iommu.h     |  324 ++++++++++
> >   linux-headers/linux/vfio.h      |   83 +++
> >   scripts/update-linux-headers.sh |    2 +-
> >   28 files changed, 2232 insertions(+), 58 deletions(-)
> >   create mode 100644 hw/iommu/Makefile.objs
> >   create mode 100644 hw/iommu/iommu.c
> >   create mode 100644 include/hw/iommu/iommu.h
> >   create mode 100644 linux-headers/linux/iommu.h
> >