linux-kernel - Re: [PATCH v2 9/9] iommu/vt-d: Store guest PASID during bind

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Message-ID: <20200910101248.19460882@jacob-builder>
Date:   Thu, 10 Sep 2020 10:12:48 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Auger Eric <eric.auger@...hat.com>
Cc:     Jacob Pan <jacob.pan.linux@...il.com>,
        iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, Wu Hao <hao.wu@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 9/9] iommu/vt-d: Store guest PASID during bind

On Tue, 1 Sep 2020 19:08:44 +0200
Auger Eric <eric.auger@...hat.com> wrote:

> Hi Jacob,
> On 8/22/20 6:35 AM, Jacob Pan wrote:
> > IOASID core maintains the guest-host mapping in the form of SPID and
> > IOASID. This patch assigns the guest PASID (if valid) as SPID while
> > binding guest page table with a host PASID. This mapping will be
> > used for lookup and notifications.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > ---
> >  drivers/iommu/intel/svm.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> > index d8a5efa75095..4c958b1aec4c 100644
> > --- a/drivers/iommu/intel/svm.c
> > +++ b/drivers/iommu/intel/svm.c
> > @@ -406,6 +406,7 @@ int intel_svm_bind_gpasid(struct iommu_domain
> > *domain, struct device *dev, if (data->flags &
> > IOMMU_SVA_GPASID_VAL) { svm->gpasid = data->gpasid;
> >  			svm->flags |= SVM_FLAG_GUEST_PASID;
> > +			ioasid_attach_spid(data->hpasid,
> > data->gpasid);  
> don't you want to handle the returned value?
Yes, I also need to add a check for duplicated SPID within a set.

> >  		}
> >  		svm->iommu = iommu;
> >  		/*
> > @@ -517,6 +518,7 @@ int intel_svm_unbind_gpasid(struct device *dev,
> > int pasid) ioasid_attach_data(pasid, NULL);
> >  				ioasid_notify(pasid, IOASID_UNBIND,
> >  					IOASID_NOTIFY_SET);
> > +				ioasid_attach_spid(pasid,
> > INVALID_IOASID);  
> So this answers my previous question ;-) but won't it enter the if
> (!ioasid_data) path and fail to reset the spid?
> 
Sorry, i am not following. If there is no ioasid_data then there is no
SPID to be stored.

BTW, I plan to separate the APIs into two.
ioasid_attach_spid
ioasid_detach_spid

Only ioasid_detach_spid will be calling synchronize RCU, then
ioasid_attach_spid can be called under spinlock.

Thanks,

> Eric
> >  				kfree(svm);
> >  			}
> >  		}
> >   
> 
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

[Jacob Pan]

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