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iommu: Generic support for RMRs during device release 

Generally an IOMMU driver should leave the translation as BLOCKED until the
translation entry is probed onto a struct device. When the struct device is
removed, the translation should be put back to BLOCKED.

Drivers that are able to work like this can set their release_domain to the
blocking domain, and the core code handles this work.

The exception is when the device has an IOMMU_RESV_DIRECT region, in which
case the OS should continuously allow translations for the given range. And
the core code generally prevents using a BLOCKED domain with this device.

Continue this logic for the device release and hoist some open coding from
drivers. If the device has dev->iommu->require_direct and the driver uses a
BLOCKED release_domain, override it to IDENTITY to preserve the semantics.

The only remaining required driver code for IOMMU_RESV_DIRECT should preset
an IDENTITY translation during early IOMMU startup for those devices.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This commit is contained in:
Jason Gunthorpe 2025-10-22 19:21:04 -07:00 committed by Joerg Roedel
parent db340b02b2
commit e94160488e
1 changed files with 14 additions and 2 deletions
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16
drivers/iommu/iommu.c
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@ -542,8 +542,20 @@ static void iommu_deinit_device(struct device *dev)
* Regardless, if a delayed attach never occurred, then the release
* should still avoid touching any hardware configuration either.
*/
if (!dev->iommu->attach_deferred && ops->release_domain)
ops->release_domain->ops->attach_dev(ops->release_domain, dev);
if (!dev->iommu->attach_deferred && ops->release_domain) {
struct iommu_domain *release_domain = ops->release_domain;
/*
* If the device requires direct mappings then it should not
* be parked on a BLOCKED domain during release as that would
* break the direct mappings.
*/
if (dev->iommu->require_direct && ops->identity_domain &&
release_domain == ops->blocked_domain)
release_domain = ops->identity_domain;
release_domain->ops->attach_dev(release_domain, dev);
}
if (ops->release_device)
ops->release_device(dev);