Re: [PATCH v5 16/19] iommu/vt-d: Misc macro clean up for SVM

[Andy Shevchenko]

On Thu, Aug 15, 2019 at 11:52 PM Jacob Pan
<jacob.jun.pan@xxxxxxxxxxxxxxx> wrote:
>
> Use combined macros for_each_svm_dev() to simplify SVM device iteration
> and error checking.
>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
> ---
>  drivers/iommu/intel-svm.c | 85 +++++++++++++++++++++++------------------------
>  1 file changed, 41 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index 5a688a5..ea6f2e2 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -218,6 +218,10 @@ static const struct mmu_notifier_ops intel_mmuops = {
>  static DEFINE_MUTEX(pasid_mutex);
>  static LIST_HEAD(global_svm_list);
>
> +#define for_each_svm_dev(svm, dev)                     \
> +       list_for_each_entry(sdev, &svm->devs, list)     \

> +       if (dev == sdev->dev)                           \

This should be
  if (dev != sdev->dev) {} else
and no trailing \ is neeeded.

The rationale of above form to avoid
for_each_foo() {
} else {
  ...WTF?!..
}

> +
>  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);
> @@ -263,15 +267,13 @@ 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(svm, dev) {
> +                               if (sdev->ops != ops) {
> +                                       ret = -EBUSY;
> +                                       goto out;
>                                 }
> +                               sdev->users++;
> +                               goto success;
>                         }
>
>                         break;
> @@ -408,48 +410,43 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
>                 goto out;
>
>         svm = ioasid_find(NULL, pasid, NULL);
> -       if (IS_ERR(svm)) {
> +       if (IS_ERR_OR_NULL(svm)) {
>                 ret = PTR_ERR(svm);
>                 goto out;
>         }
>
> -       if (!svm)
> -               goto out;
> +       for_each_svm_dev(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_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);
> -                               }
> +                               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);
> @@ -585,7 +582,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
>                          * to unbind the mm while any page faults are outstanding.
>                          * So we only need RCU to protect the internal idr code. */
>                         rcu_read_unlock();
> -                       if (IS_ERR(svm) || !svm) {
> +                       if (IS_ERR_OR_NULL(svm)) {
>                                 pr_err("%s: Page request for invalid PASID %d: %08llx %08llx\n",
>                                        iommu->name, req->pasid, ((unsigned long long *)req)[0],
>                                        ((unsigned long long *)req)[1]);
> --
> 2.7.4
>


-- 
With Best Regards,
Andy Shevchenko