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iommu: Prevent RESV_DIRECT devices from blocking domains

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The IOMMU_RESV_DIRECT flag indicates that a memory region must be mapped
1:1 at all times. This means that the region must always be accessible to
the device, even if the device is attached to a blocking domain. This is
equal to saying that IOMMU_RESV_DIRECT flag prevents devices from being
attached to blocking domains.

This also implies that devices that implement RESV_DIRECT regions will be
prevented from being assigned to user space since taking the DMA ownership
immediately switches to a blocking domain.

The rule of preventing devices with the IOMMU_RESV_DIRECT regions from
being assigned to user space has existed in the Intel IOMMU driver for
a long time. Now, this rule is being lifted up to a general core rule,
as other architectures like AMD and ARM also have RMRR-like reserved
regions. This has been discussed in the community mailing list and refer
to below link for more details.

Other places using unmanaged domains for kernel DMA must follow the
iommu_get_resv_regions() and setup IOMMU_RESV_DIRECT - we do not restrict
them in the core code.

Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/linux-iommu/BN9PR11MB5276E84229B5BD952D78E9598C639@BN9PR11MB5276.namprd11.prod.outlook.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20230724060352.113458-2-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Lu Baolu
2023-08-09 20:48:02 +08:00
committed by Joerg Roedel
parent f5ccf55e10
commit a48ce36e27
2 changed files with 29 additions and 10 deletions
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2
include/linux/iommu.h
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@@ -411,6 +411,7 @@ struct iommu_fault_param {
* @priv: IOMMU Driver private data
* @max_pasids: number of PASIDs this device can consume
* @attach_deferred: the dma domain attachment is deferred
* @require_direct: device requires IOMMU_RESV_DIRECT regions
*
* TODO: migrate other per device data pointers under iommu_dev_data, e.g.
* struct iommu_group *iommu_group;
@@ -424,6 +425,7 @@ struct dev_iommu {
void *priv;
u32 max_pasids;
u32 attach_deferred:1;
u32 require_direct:1;
};
int iommu_device_register(struct iommu_device *iommu,