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

[Jacob Pan]

On Fri, 16 Aug 2019 00:17:44 +0300
Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote:

> 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?!..
> }
> 
I understand, but until we have the else {} case we don't have anything
to avoid. The current code only has a simple positive logic.

> > +
> >  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
> >  
> 
> 

[Jacob Pan]