[PATCH v3 01/15] iommu/vt-d: Handle race between registration and device probe

[Tian, Kevin]

> From: Robin Murphy <robin.murphy at arm.com>
> Sent: Wednesday, July 6, 2022 1:08 AM
> 
> Currently we rely on registering all our instances before initially
> allowing any .probe_device calls via bus_set_iommu(). In preparation for
> phasing out the latter, make sure we won't inadvertently return success
> for a device associated with a known but not yet registered instance,
> otherwise we'll run straight into iommu_group_get_for_dev() trying to
> use NULL ops.
> 
> That also highlights an issue with intel_iommu_get_resv_regions() taking
> dmar_global_lock from within a section where intel_iommu_init() already
> holds it, which already exists via probe_acpi_namespace_devices() when
> an ANDD device is probed, but gets more obvious with the upcoming change
> to iommu_device_register(). Since they are both read locks it manages
> not to deadlock in practice, so I'm leaving it here for someone with
> more confidence to tackle a larger rework of the locking.
> 
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>

Reviewed-by: Kevin Tian <kevin.tian at intel.com>