linux-kernel - Re: [PATCH v5 8/8] iommu/vt-d: Misc macro clean up for SVM

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Date:   Tue, 3 Dec 2019 10:27:56 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Joe Perches <joe@...ches.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        Eric Auger <eric.auger@...hat.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v5 8/8] iommu/vt-d: Misc macro clean up for SVM

On Mon, 02 Dec 2019 12:10:45 -0800
Joe Perches <joe@...ches.com> wrote:

> On Mon, 2019-12-02 at 11:58 -0800, Jacob Pan wrote:
> > Use combined macros for_each_svm_dev() to simplify SVM device
> > iteration and error checking.  
> []
> > diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c  
> []
> > @@ -427,40 +430,36 @@ int intel_svm_unbind_mm(struct device *dev,
> > int pasid)  
> []
> > +	for_each_svm_dev(sdev, svm, dev) {
> > +		ret = 0;
> > +		sdev->users--;
> > +		if (!sdev->users) {  
> 
> This might be better by reducing indentation here too
> 
> 		if (sdev->users)
> 			break;
> 
> > +			list_del_rcu(&sdev->list);  
> 
> to reduce indentation 1 level below this
Sounds good but perhaps we can do this in a separate patch.

> 
> > +			/* Flush the PASID cache and IOTLB for
> > this device.
> > +			 * Note that we do depend on the hardware
> > *not* using
> > +			 * the PASID any more. Just as we depend
> > on other
> > +			 * devices never using PASIDs that they
> > have no right
> > +			 * to use. We have a *shared* PASID table,
> > because it's
> > +			 * large and has to be physically
> > contiguous. So it's
> > +			 * hard to be as defensive as we might
> > like. */
> > +			intel_pasid_tear_down_entry(iommu, dev,
> > svm->pasid);
> > +			intel_flush_svm_range_dev(svm, sdev, 0,
> > -1, 0);
> > +			kfree_rcu(sdev, rcu);
> > +
> > +			if (list_empty(&svm->devs)) {
> > +				ioasid_free(svm->pasid);
> > +				if (svm->mm)
> > +
> > mmu_notifier_unregister(&svm->notifier, svm->mm);
> > +				list_del(&svm->list);
> > +				/* We mandate that no page faults
> > may be outstanding
> > +				 * for the PASID when
> > intel_svm_unbind_mm() is called.
> > +				 * If that is not obeyed, subtle
> > errors will happen.
> > +				 * Let's make them less subtle...
> > */
> > +				memset(svm, 0x6b, sizeof(*svm));
> > +				kfree(svm);
> >  			}
> > -			break;
> >  		}
> > +		break;
> >  	}
> >   out:
> >  	mutex_unlock(&pasid_mutex);  
> 

[Jacob Pan]