Re: [PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM
On Mon, 02 Dec 2019 10:22:13 -0800
Joe Perches wrote:
> On Mon, 2019-12-02 at 10:15 -0800, Jacob Pan wrote:
> > On Thu, 21 Nov 2019 13:37:10 -0800
> > Joe Perches wrote:
> >
> > > On Thu, 2019-11-21 at 13:26 -0800, Jacob Pan wrote:
> > > > Use combined macros for_each_svm_dev() to simplify SVM device
> > > > iteration and error checking.
> > > []
> > > > diff --git a/drivers/iommu/intel-svm.c
> > > > b/drivers/iommu/intel-svm.c
> > > []
> > > > +#define for_each_svm_dev(sdev, svm, d) \
> > > > + list_for_each_entry((sdev), &(svm)->devs, list)
> > > > \
> > > > + if ((d) != (sdev)->dev) {} else
> > > > +
> > > > 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, >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;
> > > > }
> > >
> > > I think this does not read better as this is now a
> > > for_each loop that exits the loop on the first match.
> > >
> > I think one of the benefits is reduced indentation. What do you
> > recommend?
>
> Making the code intelligible for a reader.
>
> At least add a comment describing why there is only
> a single possible match.
>
> Given the for_each name, it's odd code that only the
> first match has an action.
>
I will add a comment to explain we are trying to find the matching
device on the list.
Thanks
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Re: [PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM
On Mon, 2019-12-02 at 10:15 -0800, Jacob Pan wrote:
> On Thu, 21 Nov 2019 13:37:10 -0800
> Joe Perches wrote:
>
> > On Thu, 2019-11-21 at 13:26 -0800, Jacob Pan wrote:
> > > Use combined macros for_each_svm_dev() to simplify SVM device
> > > iteration and error checking.
> > []
> > > diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> > []
> > > +#define for_each_svm_dev(sdev, svm, d) \
> > > + list_for_each_entry((sdev), &(svm)->devs, list) \
> > > + if ((d) != (sdev)->dev) {} else
> > > +
> > > 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, >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;
> > > }
> >
> > I think this does not read better as this is now a
> > for_each loop that exits the loop on the first match.
> >
> I think one of the benefits is reduced indentation. What do you
> recommend?
Making the code intelligible for a reader.
At least add a comment describing why there is only
a single possible match.
Given the for_each name, it's odd code that only the
first match has an action.
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Re: [PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM
On Thu, 21 Nov 2019 13:37:10 -0800
Joe Perches wrote:
> On Thu, 2019-11-21 at 13:26 -0800, Jacob Pan wrote:
> > Use combined macros for_each_svm_dev() to simplify SVM device
> > iteration and error checking.
> []
> > diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> []
> > +#define for_each_svm_dev(sdev, svm, d) \
> > + list_for_each_entry((sdev), &(svm)->devs, list) \
> > + if ((d) != (sdev)->dev) {} else
> > +
> > 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, >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;
> > }
>
> I think this does not read better as this is now a
> for_each loop that exits the loop on the first match.
>
I think one of the benefits is reduced indentation. What do you
recommend?
> >
> > break;
> > @@ -427,43 +429,36 @@ int intel_svm_unbind_mm(struct device *dev,
> > int pasid) goto out;
> > }
> >
> > - if (!svm)
> > - goto out;
> > -
> > - list_for_each_entry(sdev, >devs, list) {
> []
> > + for_each_svm_dev(sdev, svm, dev) {
>
> I think this should not remove the !svm test above.
>
Yeah, !svm test should have been part of 6/8. I will fix that.
Thanks,
Jacob
>
[Jacob Pan]
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Re: [PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM
On Thu, 2019-11-21 at 13:26 -0800, Jacob Pan wrote:
> Use combined macros for_each_svm_dev() to simplify SVM device iteration
> and error checking.
[]
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
[]
> +#define for_each_svm_dev(sdev, svm, d) \
> + list_for_each_entry((sdev), &(svm)->devs, list) \
> + if ((d) != (sdev)->dev) {} else
> +
> 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, >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;
> }
I think this does not read better as this is now a
for_each loop that exits the loop on the first match.
>
> break;
> @@ -427,43 +429,36 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
> goto out;
> }
>
> - if (!svm)
> - goto out;
> -
> - list_for_each_entry(sdev, >devs, list) {
[]
> + for_each_svm_dev(sdev, svm, dev) {
I think this should not remove the !svm test above.
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[PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM
Use combined macros for_each_svm_dev() to simplify SVM device iteration
and error checking.
Suggested-by: Andy Shevchenko
Signed-off-by: Jacob Pan
Reviewed-by: Eric Auger
Acked-by: Lu Baolu
---
drivers/iommu/intel-svm.c | 81 ++-
1 file changed, 38 insertions(+), 43 deletions(-)
diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 4eecc24412dc..5b4224871e34 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, d) \
+ list_for_each_entry((sdev), &(svm)->devs, list) \
+ if ((d) != (sdev)->dev) {} else
+
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, >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;
@@ -427,43 +429,36 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
goto out;
}
- if (!svm)
- goto out;
-
- list_for_each_entry(sdev, >devs, list) {
- if (dev == sdev->dev) {
- ret = 0;
- sdev->users--;
- if (!sdev->users) {
- list_del_rcu(>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(>devs)) {
- ioasid_free(svm->pasid);
- if (svm->mm)
-
mmu_notifier_unregister(>notifier, svm->mm);
-
- list_del(>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(>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);
+
