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

[Baolu Lu]

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?

--
Best regards,
baolu