Hi Baolu, On Mon, Oct 26, 2020 at 02:30:08PM +0800, Lu Baolu wrote: > @@ -264,7 +266,8 @@ int iommu_probe_device(struct device *dev) > */ > iommu_alloc_default_domain(group, dev); > > - if (group->default_domain) > + if (group->default_domain && > + !iommu_is_attach_deferred(group->default_domain, dev)) > ret = __iommu_attach_device(group->default_domain, dev); This is the hotplug path, not used for boot-initialization. Have you seen failures from the missing check here? Regards, Joerg