linux-kernel - RE: [PATCH v1 5/8] vfio/type1: Report 1st-level/stage-1 format to userspace

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Date:   Wed, 8 Apr 2020 01:02:51 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Auger Eric <eric.auger@...hat.com>
CC:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>,
        "Sun, Yi Y" <yi.y.sun@...el.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Wu, Hao" <hao.wu@...el.com>
Subject: RE: [PATCH v1 5/8] vfio/type1: Report 1st-level/stage-1 format to
 userspace

> From: Liu, Yi L
> Sent: Tuesday, April 7, 2020 5:43 PM
>
> > We don't, the PASID spaces are per-VM on Arm, so this function should
> > consult the IOMMU driver before setting flags. As you said on patch 3,
> > nested doesn't necessarily imply PASID support. The SMMUv2 does not
> > support PASID but does support nesting stages 1 and 2 for the IOVA space.
> > SMMUv3 support of PASID depends on HW capabilities. So I think this
> > needs to be finer grained:
> >
> > Does the container support:
> > * VFIO_IOMMU_PASID_REQUEST?
> >   -> Yes for VT-d 3
> >   -> No for Arm SMMU
> > * VFIO_IOMMU_{,UN}BIND_GUEST_PGTBL?
> >   -> Yes for VT-d 3
> >   -> Sometimes for SMMUv2
> >   -> No for SMMUv3 (if we go with BIND_PASID_TABLE, which is simpler due to
> >      PASID tables being in GPA space.)
> > * VFIO_IOMMU_BIND_PASID_TABLE?
> >   -> No for VT-d
> >   -> Sometimes for SMMUv3
> >
> > Any bind support implies VFIO_IOMMU_CACHE_INVALIDATE support.
> 
> good summary. do you expect to see any
please ignore this message. I planned to ask if possible to report
VFIO_IOMMU_CACHE_INVALIDATE  only (no bind support). But I stopped
typing it when I came to believe it's unnecessary to report it if
there is no bind support.

Regards,
Yi Liu