Re: [PATCH v4 10/19] iommu: Add set_platform_dma_ops iommu ops

[Baolu Lu]

On 1/5/23 9:15 PM, Jason Gunthorpe wrote:
> On Thu, Jan 05, 2023 at 01:58:42PM +0800, Baolu Lu wrote:
> > Hi Jason,
> >
> > On 2023/1/4 21:17, Jason Gunthorpe wrote:
> > > On Wed, Jan 04, 2023 at 08:57:16PM +0800, Lu Baolu wrote:
> > >
> > > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > > > index de91dd88705b..4e35a9f94873 100644
> > > > --- a/drivers/iommu/iommu.c
> > > > +++ b/drivers/iommu/iommu.c
> > > > @@ -2163,6 +2163,17 @@ static int iommu_group_do_detach_device(struct device *dev, void *data)
> > > >    	return 0;
> > > >    }
> > > > +static int iommu_group_do_set_platform_dma(struct device *dev, void *data)
> > > > +{
> > > > +	const struct iommu_ops *ops = dev_iommu_ops(dev);
> > > > +
> > > > +	if (!ops->set_platform_dma_ops)
> > > > +		return -EINVAL;
> > > > +
> > > > +	ops->set_platform_dma_ops(dev);
> > > > +	return 0;
> > > > +}
> > > > +
> > > >    static int __iommu_group_set_domain(struct iommu_group *group,
> > > >    				    struct iommu_domain *new_domain)
> > > >    {
> > > > @@ -2177,10 +2188,14 @@ static int __iommu_group_set_domain(struct iommu_group *group,
> > > >    	 * platform specific behavior.
> > > >    	 */
> > > >    	if (!new_domain) {
> > > > -		if (WARN_ON(!group->domain->ops->detach_dev))
> > > > -			return -EINVAL;
> > > This should still have the WARN_ON..
> > >
> > > if (WARN_ON(!group->domain->ops->detach_dev && !dev_iommu_ops(dev)->set_platform_dma_ops)
> > This has been implicitly included in the code.
> >
> > iommu_group_do_set_platform_dma() returns -EINVAL if the iommu driver
> > doesn't support set_platform_dma_ops (otherwise always return success).
> > Then, the domain->ops->detach_dev is required and a WARN_ON was there.
> >
> >          if (!new_domain) {
> >                  ret = __iommu_group_for_each_dev(group, NULL,
> >                                  iommu_group_do_set_platform_dma);
> >                  if (ret) {
> >                          if (WARN_ON(!group->domain->ops->detach_dev))
> >                                  return -EINVAL;
> >                          __iommu_group_for_each_dev(group, group->domain,
> >                                  iommu_group_do_detach_device);
> >                  }
> >                  group->domain = NULL;
> >                  return 0;
> >          }
> >
> > Perhaps I should add a comment to explain this?
> But you delete this later when you remove this.
>
> I think testing the op directly is much clearer, get rid of the whole
> ret and EINVAL thinig:
>
> if (dev_iommu_ops(dev)->set_platform_dma_ops)
>     __iommu_group_for_each_dev(group, NULL,
>                                   iommu_group_do_set_platform_dma); //	 Can't fail!
> else if (group->domain->ops->detach_dev)
>       __iommu_group_for_each_dev(group, group->domain,
>                                   iommu_group_do_detach_device);
> else
>     WARN(true)

Above looks good to me. Thanks! I have updated this part of code like
below:

@@ -2177,10 +2188,20 @@ static int __iommu_group_set_domain(struct 
iommu_group *group,
         * platform specific behavior.
         */
        if (!new_domain) {
-               if (WARN_ON(!group->domain->ops->detach_dev))
-                       return -EINVAL;
-               __iommu_group_for_each_dev(group, group->domain,
-                                          iommu_group_do_detach_device);
+               struct group_device *grp_dev;
+
+               grp_dev = list_first_entry(&group->devices,
+                                          struct group_device, list);
+
+               if (dev_iommu_ops(grp_dev->dev)->set_platform_dma_ops)
+                       __iommu_group_for_each_dev(group, NULL,
+                                       iommu_group_do_set_platform_dma);
+               else if (group->domain->ops->detach_dev)
+                       __iommu_group_for_each_dev(group, group->domain,
+                                       iommu_group_do_detach_device);
+               else
+                       WARN_ON_ONCE(1);
+
                group->domain = NULL;
                return 0;
        }

--
Best regards,
baolu