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

Baolu Lu
2023-01-06T06:16:05Z

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