linux-kernel - Re: [PATCH v4 19/22] iommu/vt-d: Clean up for SVM device list

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Message-ID: <20190618174237.00000556@huawei.com>
Date:   Tue, 18 Jun 2019 17:42:37 +0100
From:   Jonathan Cameron <jonathan.cameron@...wei.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
CC:     <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "Eric Auger" <eric.auger@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v4 19/22] iommu/vt-d: Clean up for SVM device list

On Sun, 9 Jun 2019 06:44:19 -0700
Jacob Pan <jacob.jun.pan@...ux.intel.com> wrote:

> Use combined macro for_each_svm_dev() to simplify SVM device iteration.
> 
> 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 | 79 +++++++++++++++++++++++------------------------
>  1 file changed, 39 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index 9cbcc1f..66d98e1 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -225,6 +225,9 @@ static const struct mmu_notifier_ops intel_mmuops = {
>  
>  static DEFINE_MUTEX(pasid_mutex);
>  static LIST_HEAD(global_svm_list);
> +#define for_each_svm_dev() \
> +	list_for_each_entry(sdev, &svm->devs, list)	\
> +	if (dev == sdev->dev)				\

Could we make this macro less opaque and have it take the svm and dev as
arguments?

>  
>  int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ops *ops)
>  {
> @@ -271,15 +274,13 @@ 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() {
> +				if (sdev->ops != ops) {
> +					ret = -EBUSY;
> +					goto out;
>  				}
> +				sdev->users++;
> +				goto success;
>  			}
>  
>  			break;
> @@ -409,40 +410,38 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
>  	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, !svm->mm);
> -				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);
> -				}
> +	for_each_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, !svm->mm);
> +			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);