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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 the only caller is VFIO no-iommu which never associates with an iommu driver. Thus adding this additional check is safe. Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Link: https://lore.kernel.org/r/1-v3-328044aa278c+45e49-iommu_probe_jgg@nvidia.com Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.