Re: [PATCH 00/10] iommu/vt-d: Add scalable mode support

[Jacob Pan]

On Mon, 16 Jul 2018 11:51:57 +0100
Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx> wrote:

> Hi,
> 
> On 16/07/18 07:49, Lu Baolu wrote:
> > Intel vt-d rev3.0 [1] introduces a new translation mode called
> > 'scalable mode', which enables PASID-granular translations for
> > first level, second level, nested and pass-through modes. The
> > vt-d scalable mode is the key ingredient to enable Scalable I/O
> > Virtualization (Scalable IOV) [2] [3], which allows sharing a
> > device in minimal possible granularity (ADI - Assignable Device
> > Interface). It also includes all the capabilities required to
> > enable Shared Virtual Addressing (SVA). As a result, previous
> > Extended Context (ECS) mode is deprecated (no production ever
> > implements ECS).
> > 
> > Each scalable mode pasid table entry is 64 bytes in length, with
> > fields point to the first level page table and the second level
> > page table. The PGTT (Pasid Granular Translation Type) field is
> > used by hardware to determine the translation type.  
> 
> Looks promising! Since the 2nd level page tables are in the PASID
> entry, the hypervisor traps guest accesses to the PASID tables
> instead of passing through the whole PASID directory? Are you still
> planning to use the VFIO BIND_PASID_TABLE interface in this mode, or
> a slightly different one for individual PASIDs?
> 
Since we deprecated ECS mode, there is no need for VT-d to bind guest
pasid table in scalable mode. We are planning on adding another flag for
bind guest pasid and guest CR3, Perhaps call it
VFIO_IOMMU_BIND_GUEST_SVA.
> Thanks,
> Jean
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[Jacob Pan]