On Tue, Aug 20, 2019 at 07:42:25PM -0700, Sai Praneeth Prakhya wrote:
> + /*
> + * iommu_domain_alloc() takes "struct bus_type" as an argument which is
> + * a member in "struct device". Changing a group's default domain type
> + * deals at iommu_group level rather than device level and hence there
> + * is no straight forward way to get "bus_type" of an iommu_group that
> + * could be passed to iommu_domain_alloc(). So, instead of directly
> + * calling iommu_domain_alloc(), use iommu_ops from previous default
> + * domain.
> + */
> + if (!prev_domain || !prev_domain->ops ||
> + !prev_domain->ops->domain_alloc || !type)
> + return -EINVAL;
Hmm, this isn't really nice and clean, but I understand why you need it.
I will think about a better way to get iommu_ops here.
> +free_prev_domain:
> + /*
> + * Free the existing default domain and replace it with the newly
> + * created default domain. No need to set group->domain because
> + * __iommu_attach_group() already does it on success.
> + */
> + iommu_domain_free(prev_domain);
> + group->default_domain = new_domain;
> + return 0;
It isn't obvious to me from this patch, how to are the dma_ops updated
when the default domain changes between identity and dma?
> + /* Check if any device in the group still has a driver binded to it */
> + if (iommu_group_for_each_dev(group, NULL, is_driver_binded)) {
> + pr_err("Active drivers exist for devices in the group\n");
> + return -EBUSY;
> + }
This is racy with device driver probing code. Unfortunatly there is no
clean way out of that either, locking all devices in the group and then
do the re-attach will introduce a lock-inversion with group->mutex. But
please put a comment here saying that this might race with device driver
probing.
Regards,
Joerg
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