linux-kernel - Re: [PATCH 10/10] iommu/vt-d: Misc macro clean up for SVM

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Date:   Mon, 18 Nov 2019 10:23:34 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.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>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     baolu.lu@...ux.intel.com, "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>
Subject: Re: [PATCH 10/10] iommu/vt-d: Misc macro clean up for SVM

Hi,

On 11/16/19 7:09 AM, Jacob Pan wrote:
> Use combined macros for_each_svm_dev() to simplify SVM device iteration
> and error checking.
> 
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Reviewed-by: Eric Auger <eric.auger@...hat.com>
> ---
>   drivers/iommu/intel-svm.c | 85 ++++++++++++++++++++++-------------------------
>   1 file changed, 40 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index 189865501411..a7f67a9da3fc 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -226,6 +226,10 @@ static const struct mmu_notifier_ops intel_mmuops = {
>   static DEFINE_MUTEX(pasid_mutex);
>   static LIST_HEAD(global_svm_list);
>   
> +#define for_each_svm_dev(sdev, svm, dev)		\
> +	list_for_each_entry(sdev, &svm->devs, list)	\
> +		if (dev != sdev->dev) {} else

"dev" has been reused in "sdev->dev", how about below?

#define for_each_svm_dev(sdev, svm, d)                  \
         list_for_each_entry((sdev), &(svm)->devs, list) \
                 if ((d) != (sdev)->dev) {} else

Best regards,
baolu


> +
>   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;
>   			}
>   
>   			break;
> @@ -427,45 +429,38 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
>   		goto out;
>   	}
>   
> -	if (!svm)
> -		goto out;
> -
> -	list_for_each_entry(sdev, &svm->devs, list) {
> -		if (dev == sdev->dev) {
> -			ret = 0;
> -			sdev->users--;
> -			if (!sdev->users) {
> -				list_del_rcu(&sdev->list);
> -				/* 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)) {
> -					/* Clear private data so that free pass check */
> -					ioasid_set_data(svm->pasid, NULL);
> -					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);
> -				}
> +	for_each_svm_dev(sdev, svm, dev) {
> +		ret = 0;
> +		sdev->users--;
> +		if (!sdev->users) {
> +			list_del_rcu(&sdev->list);
> +			/* 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)) {
> +				/* Clear private data so that free pass check */
> +				ioasid_set_data(svm->pasid, NULL);
> +				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);
>