linux-kernel - Re: [PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM

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Date:   Thu, 21 Nov 2019 13:37:10 -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 v4 8/8] iommu/vt-d: Misc macro clean up for SVM

On Thu, 2019-11-21 at 13:26 -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
[]
> +#define for_each_svm_dev(sdev, svm, d)			\
> +	list_for_each_entry((sdev), &(svm)->devs, list)	\
> +		if ((d) != (sdev)->dev) {} else
> +
>  int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ops *ops)
>  {
>  	struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> @@ -274,15 +278,13 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_
>  				goto out;
>  			}
>  
> -			list_for_each_entry(sdev, &svm->devs, list) {
> -				if (dev == sdev->dev) {
> -					if (sdev->ops != ops) {
> -						ret = -EBUSY;
> -						goto out;
> -					}
> -					sdev->users++;
> -					goto success;
> +			for_each_svm_dev(sdev, svm, dev) {
> +				if (sdev->ops != ops) {
> +					ret = -EBUSY;
> +					goto out;
>  				}
> +				sdev->users++;
> +				goto success;
>  			}

I think this does not read better as this is now a
for_each loop that exits the loop on the first match.

>  
>  			break;
> @@ -427,43 +429,36 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
>  		goto out;
>  	}
>  
> -	if (!svm)
> -		goto out;
> -
> -	list_for_each_entry(sdev, &svm->devs, list) {
[]
> +	for_each_svm_dev(sdev, svm, dev) {

I think this should not remove the !svm test above.