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SubjectRe: [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest
Hi Jacob

On Mon, Sep 23, 2019 at 12:27:15PM -0700, Jacob Pan wrote:
> >
> > In VT-d 3.0, scalable mode is introduced, which offers two level
> > translation page tables and nested translation mode. Regards to
> > GIOVA support, it can be simplified by 1) moving the GIOVA support
> > over 1st-level page table to store GIOVA->GPA mapping in vIOMMU,
> > 2) binding vIOMMU 1st level page table to the pIOMMU, 3) using pIOMMU
> > second level for GPA->HPA translation, and 4) enable nested (a.k.a.
> > dual stage) translation in host. Compared with current shadow GIOVA
> > support, the new approach is more secure and software is simplified
> > as we only need to flush the pIOMMU IOTLB and possible device-IOTLB
> > when an IOVA mapping in vIOMMU is torn down.
> >
> > .-----------.
> > | vIOMMU |
> > |-----------| .-----------.
> > | |IOTLB flush trap | QEMU |
> > .-----------. (unmap) |-----------|
> > | GVA->GPA |---------------->| |
> > '-----------' '-----------'
> > | | |
> > '-----------' |
> > <------------------------------
> > | VFIO/IOMMU
> > | cache invalidation and
> > | guest gpd bind interfaces
> > v
> For vSVA, the guest PGD bind interface will mark the PASID as guest
> PASID and will inject page request into the guest. In FL gIOVA case, I
> guess we are assuming there is no page fault for GIOVA. I will need to
> add a flag in the gpgd bind such that any PRS will be auto responded
> with invalid.

Is there real need to enforce this? I'm not sure if there is any
limitation in the spec, and if so, can the guest check that instead?

Also i believe the idea is to overcommit PASID#0 such uses. Thought
we had a capability to expose this to the vIOMMU as well. Not sure if this
is already documented, if not should be up in the next rev.


>
> Also, native use of IOVA FL map is not to be supported? i.e. IOMMU API
> and DMA API for native usage will continue to be SL only?
> > .-----------.
> > | pIOMMU |
> > |-----------|
> > .-----------.
> > | GVA->GPA |<---First level
> > '-----------'
> > | GPA->HPA |<---Scond level

s/Scond/Second

> > '-----------'
> > '-----------'
> >
> > This patch series only aims to achieve the first goal, a.k.a using
> > first level translation for IOVA mappings in vIOMMU. I am sending
> > it out for your comments. Any comments, suggestions and concerns are
> > welcomed.
> >
>
>
> > Based-on-idea-by: Ashok Raj <ashok.raj@intel.com>
> > Based-on-idea-by: Kevin Tian <kevin.tian@intel.com>
> > Based-on-idea-by: Liu Yi L <yi.l.liu@intel.com>
> > Based-on-idea-by: Lu Baolu <baolu.lu@linux.intel.com>
> > Based-on-idea-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
> >
> > Lu Baolu (4):
> > iommu/vt-d: Move domain_flush_cache helper into header
> > iommu/vt-d: Add first level page table interfaces
> > iommu/vt-d: Map/unmap domain with mmmap/mmunmap
> > iommu/vt-d: Identify domains using first level page table
> >
> > drivers/iommu/Makefile | 2 +-
> > drivers/iommu/intel-iommu.c | 142 ++++++++++--
> > drivers/iommu/intel-pgtable.c | 342
> > +++++++++++++++++++++++++++++ include/linux/intel-iommu.h |
> > 31 ++- include/trace/events/intel_iommu.h | 60 +++++
> > 5 files changed, 553 insertions(+), 24 deletions(-)
> > create mode 100644 drivers/iommu/intel-pgtable.c
> >
>
> [Jacob Pan]

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