> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Thursday, April 20, 2023 12:12 AM > > This is a step toward making __iommu_probe_device() self contained. > > It should, under proper locking, check if the device is already associated > with an iommu driver and resolve parallel probes. All but one of the > callers open code this test using two different means, but they all > rely on dev->iommu_group. > > Currently the bus_iommu_probe()/probe_iommu_group() and > probe_acpi_namespace_devices() rejects already probed devices with an > unlocked read of dev->iommu_group. The OF and ACPI "replay" functions > use > device_iommu_mapped() which is the same read without the pointless > refcount. > > Move this test into __iommu_probe_device() and put it under the > iommu_probe_device_lock. The store to dev->iommu_group is in > iommu_group_add_device() which is also called under this lock for iommu > driver devices, making it properly locked. > > The only path that didn't have this check is the hotplug path triggered by > BUS_NOTIFY_ADD_DEVICE. The only way to get dev->iommu_group assigned > outside the probe path is via iommu_group_add_device(). Today there are > only three callers, VFIO no-iommu, powernv and power pseries - none of > these cases probe iommu drivers. Thus adding this additional check is > safe. > > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
