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

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Date:   Mon, 02 Dec 2019 12:10:45 -0800
From:   Joe Perches <joe@...ches.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        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>
Cc:     "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>
Subject: Re: [PATCH v5 8/8] iommu/vt-d: Misc macro clean up for SVM

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

> +			/* 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);