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

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Message-ID: <20180718174702.31e1c1d6@jacob-builder>
Date:   Wed, 18 Jul 2018 17:47:02 -0700
From:   Jacob Pan <jacob.jun.pan@...el.com>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>, ashok.raj@...el.com,
        sanjay.k.kumar@...el.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, yi.y.sun@...el.com,
        jacob.jun.pan@...el.com
Subject: Re: [PATCH 00/10] iommu/vt-d: Add scalable mode support

On Mon, 16 Jul 2018 11:51:57 +0100
Jean-Philippe Brucker <jean-philippe.brucker@....com> 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
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

[Jacob Pan]

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