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SubjectRe: [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@linux.intel.com> wrote:

> Use combined macro for_each_svm_dev() to simplify SVM device iteration.
>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.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);


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