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From: "Liu, Yi L" <yi.l.liu@intel.com>
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Subject: RE: Support SVM without PASID
Date: Sun, 9 Jul 2017 09:29:21 +0000
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> -----Original Message-----
> From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
> bounces@lists.linux-foundation.org] On Behalf Of valmiki
> Sent: Sunday, July 9, 2017 11:16 AM
> To: Alex Williamson <alex.williamson@redhat.com>
> Cc: Lan, Tianyu <tianyu.lan@intel.com>; Tian, Kevin <kevin.tian@intel.com>;
> kvm@vger.kernel.org; linux-pci@vger.kernel.org; iommu@lists.linux-foundation.org;
> Pan, Jacob jun <jacob.jun.pan@intel.com>
> Subject: Re: Support SVM without PASID
> 
> >> Hi,
> >>
> >> In SMMUv3 architecture document i see "PASIDs are optional,
> >> configurable, and of a size determined by the minimum of the
> >> endpoint".
> >>
> >> So if PASID's are optional and not supported by PCIe end point, how
> >> SVM can be achieved ?
> >
> > It cannot be inferred from that statement that PASID support is not
> > required for SVM.  AIUI, SVM is a software feature enabled by numerous
> > "optional" hardware features, including PASID.  Features that are
> > optional per the hardware specification may be required for specific
> > software features.  Thanks,
> >
> Thanks for the information Alex. Suppose if an End point doesn't support PASID, is it
> still possible to achieve SVM ?
> Are there any such features in SMMUv3 with which we can achieve it ?

If endpoint has no PASID support, I don't think it is SVM capable. For SMMU, maybe
you can get more info from Jean.

Regards,
Yi L