linux-kernel - Re: [PATCH V10 06/11] iommu/vt-d: Add bind guest PASID support

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Date:   Wed, 1 Apr 2020 10:13:30 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "Alex Williamson" <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Jonathan Cameron" <jic23@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH V10 06/11] iommu/vt-d: Add bind guest PASID support

On Tue, 31 Mar 2020 03:43:39 +0000
"Tian, Kevin" <kevin.tian@...el.com> wrote:

> > > >  struct intel_svm_dev {
> > > > @@ -698,9 +700,13 @@ struct intel_svm_dev {
> > > >  struct intel_svm {
> > > >  	struct mmu_notifier notifier;
> > > >  	struct mm_struct *mm;
> > > > +
> > > >  	struct intel_iommu *iommu;
> > > >  	int flags;
> > > >  	int pasid;
> > > > +	int gpasid; /* Guest PASID in case of vSVA bind with
> > > > non-identity host
> > > > +		     * to guest PASID mapping.
> > > > +		     */  
> > >
> > > we don't need to highlight identity or non-identity thing, since
> > > either way shares the same infrastructure here and it is not the
> > > knowledge that the kernel driver should assume
> > >  
> > Sorry, I don't get your point.
> > 
> > What I meant was that this field "gpasid" is only used for
> > non-identity case. For identity case, we don't have
> > SVM_FLAG_GUEST_PASID.  
> 
> what's the problem if a guest tries to set gpasid even in identity
> case? do you want to add check to reject it? Also I remember we
> discussed before that we want to provide a consistent interface 
> to other consumer e.g. KVM to setup VMCS PASID translation table.
> In that case, regardless of identity or non-identity, we need provide
> such mapping info.
The solution is in flux a little. For KVM to set up VMCS, we are
planning to use IOASID set private ID as guest PASID. So this part of
the code will go away, i.e. G-H PASID mapping will no longer stored in
IOMMU driver. Perhaps we can address this after the transition?