[RFC PATCH 11/13] iommu: Add callback to restore persisted iommu_domain

James Gowans
2024-09-16T11:35:12Z

The previous commits re-hydrated the struct iommu_domain and added them
to the persisted_domains xarray. Now provide a callback to get the
domain so that iommufd can restore a link to it.

Roughly where the restore would happen is called out in a comment, but
some more head scratching is needed to figure out how to actually do
this.
---
drivers/iommu/intel/iommu.c | 12 ++++++++++++
drivers/iommu/iommufd/serialise.c | 9 ++++++++-
include/linux/iommu.h | 5 +++++
3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 8e0ed033b03f..000ddfe5b6de 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4690,6 +4690,17 @@ static int intel_iommu_read_and_clear_dirty(struct iommu_domain *domain,
return 0;
}

+static struct iommu_domain *intel_domain_restore(struct device *dev,
+ unsigned long persistent_id)
+{
+ struct iommu_domain *domain;
+
+ domain = xa_load(&persistent_domains, persistent_id);
+ if (!domain)
+ pr_warn("No such persisted domain id %lu\n", persistent_id);
+ return domain;
+}
+
static const struct iommu_dirty_ops intel_dirty_ops = {
.set_dirty_tracking = intel_iommu_set_dirty_tracking,
.read_and_clear_dirty = intel_iommu_read_and_clear_dirty,
@@ -4703,6 +4714,7 @@ const struct iommu_ops intel_iommu_ops = {
.domain_alloc = intel_iommu_domain_alloc,
.domain_alloc_user = intel_iommu_domain_alloc_user,
.domain_alloc_sva = intel_svm_domain_alloc,
+ .domain_restore = intel_domain_restore,
.probe_device = intel_iommu_probe_device,
.release_device = intel_iommu_release_device,
.get_resv_regions = intel_iommu_get_resv_regions,
diff --git a/drivers/iommu/iommufd/serialise.c b/drivers/iommu/iommufd/serialise.c
index 9519969bd201..baac7d6150cb 100644
--- a/drivers/iommu/iommufd/serialise.c
+++ b/drivers/iommu/iommufd/serialise.c
@@ -139,7 +139,14 @@ static int rehydrate_iommufd(char *iommufd_name)
area->node.last = *iova_start + *iova_len - 1;
interval_tree_insert(&area->node, &ioas->iopt.area_itree);
}
- /* TODO: restore link from ioas to hwpt. */
+ /*
+ * Here we should do something to associate struct iommufd_device with the
+ * ictx, then get the iommu_ops via dev_iommu_ops(), and call the new
+ * .domain_restore callback to get the struct iommu_domain.
+ * Something like:
+ * hwpt->domain = ops->domain_restore(dev, persistent_id);
+ * Hand wavy - the details allude me at the moment...
+ */
}

return fd;
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index a616e8702a1c..0dc97d494fd9 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -529,6 +529,8 @@ static inline int __iommu_copy_struct_from_user_array(
* @domain_alloc_paging: Allocate an iommu_domain that can be used for
* UNMANAGED, DMA, and DMA_FQ domain types.
* @domain_alloc_sva: Allocate an iommu_domain for Shared Virtual Addressing.
+ * @domain_restore: After kexec, give the same persistent_id which was originally
+ * used to allocate the domain, and the domain will be restored.
* @probe_device: Add device to iommu driver handling
* @release_device: Remove device from iommu driver handling
* @probe_finalize: Do final setup work after the device is added to an IOMMU
@@ -576,6 +578,9 @@ struct iommu_ops {
struct iommu_domain *(*domain_alloc_sva)(struct device *dev,
struct mm_struct *mm);

+ struct iommu_domain *(*domain_restore)(struct device *dev,
+ unsigned long persistent_id);
+
struct iommu_device *(*probe_device)(struct device *dev);
void (*release_device)(struct device *dev);
void (*probe_finalize)(struct device *dev);
--
2.34.1