5 files changed, 97 insertions, 0 deletions
diff --git a/drivers/iommu/iommufd/Makefile b/drivers/iommu/iommufd/Makefile
index 2b4f36f1b72f..e13e971aa28c 100644
--- a/drivers/iommu/iommufd/Makefile
+++ b/drivers/iommu/iommufd/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 iommufd-y := \
+	hw_pagetable.o \
 	io_pagetable.o \
 	ioas.o \
 	main.o \
diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
new file mode 100644
index 000000000000..43d473989a06
--- /dev/null
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
+ */
+#include <linux/iommu.h>
+
+#include "iommufd_private.h"
+
+void iommufd_hw_pagetable_destroy(struct iommufd_object *obj)
+{
+	struct iommufd_hw_pagetable *hwpt =
+		container_of(obj, struct iommufd_hw_pagetable, obj);
+
+	WARN_ON(!list_empty(&hwpt->devices));
+
+	iommu_domain_free(hwpt->domain);
+	refcount_dec(&hwpt->ioas->obj.users);
+	mutex_destroy(&hwpt->devices_lock);
+}
+
+/**
+ * iommufd_hw_pagetable_alloc() - Get an iommu_domain for a device
+ * @ictx: iommufd context
+ * @ioas: IOAS to associate the domain with
+ * @dev: Device to get an iommu_domain for
+ *
+ * Allocate a new iommu_domain and return it as a hw_pagetable.
+ */
+struct iommufd_hw_pagetable *
+iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
+			   struct device *dev)
+{
+	struct iommufd_hw_pagetable *hwpt;
+	int rc;
+
+	hwpt = iommufd_object_alloc(ictx, hwpt, IOMMUFD_OBJ_HW_PAGETABLE);
+	if (IS_ERR(hwpt))
+		return hwpt;
+
+	hwpt->domain = iommu_domain_alloc(dev->bus);
+	if (!hwpt->domain) {
+		rc = -ENOMEM;
+		goto out_abort;
+	}
+
+	INIT_LIST_HEAD(&hwpt->devices);
+	INIT_LIST_HEAD(&hwpt->hwpt_item);
+	mutex_init(&hwpt->devices_lock);
+	/* Pairs with iommufd_hw_pagetable_destroy() */
+	refcount_inc(&ioas->obj.users);
+	hwpt->ioas = ioas;
+	return hwpt;
+
+out_abort:
+	iommufd_object_abort(ictx, &hwpt->obj);
+	return ERR_PTR(rc);
+}
diff --git a/drivers/iommu/iommufd/ioas.c b/drivers/iommu/iommufd/ioas.c
index 6ff97dafc891..302779b33bd4 100644
--- a/drivers/iommu/iommufd/ioas.c
+++ b/drivers/iommu/iommufd/ioas.c
@@ -17,6 +17,7 @@ void iommufd_ioas_destroy(struct iommufd_object *obj)
 	rc = iopt_unmap_all(&ioas->iopt, NULL);
 	WARN_ON(rc && rc != -ENOENT);
 	iopt_destroy_table(&ioas->iopt);
+	mutex_destroy(&ioas->mutex);
 }
 
 struct iommufd_ioas *iommufd_ioas_alloc(struct iommufd_ctx *ictx)
@@ -28,6 +29,8 @@ struct iommufd_ioas *iommufd_ioas_alloc(struct iommufd_ctx *ictx)
 		return ioas;
 
 	iopt_init_table(&ioas->iopt);
+	INIT_LIST_HEAD(&ioas->hwpt_list);
+	mutex_init(&ioas->mutex);
 	return ioas;
 }
 
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 1a13c54a8def..6b0448702a95 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -103,6 +103,7 @@ static inline int iommufd_ucmd_respond(struct iommufd_ucmd *ucmd,
 enum iommufd_object_type {
 	IOMMUFD_OBJ_NONE,
 	IOMMUFD_OBJ_ANY = IOMMUFD_OBJ_NONE,
+	IOMMUFD_OBJ_HW_PAGETABLE,
 	IOMMUFD_OBJ_IOAS,
 };
 
@@ -181,10 +182,20 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
  * io_pagetable object. It is a user controlled mapping of IOVA -> PFNs. The
  * mapping is copied into all of the associated domains and made available to
  * in-kernel users.
+ *
+ * Every iommu_domain that is created is wrapped in a iommufd_hw_pagetable
+ * object. When we go to attach a device to an IOAS we need to get an
+ * iommu_domain and wrapping iommufd_hw_pagetable for it.
+ *
+ * An iommu_domain & iommfd_hw_pagetable will be automatically selected
+ * for a device based on the hwpt_list. If no suitable iommu_domain
+ * is found a new iommu_domain will be created.
  */
 struct iommufd_ioas {
 	struct iommufd_object obj;
 	struct io_pagetable iopt;
+	struct mutex mutex;
+	struct list_head hwpt_list;
 };
 
 static inline struct iommufd_ioas *iommufd_get_ioas(struct iommufd_ucmd *ucmd,
@@ -207,6 +218,28 @@ int iommufd_ioas_option(struct iommufd_ucmd *ucmd);
 int iommufd_option_rlimit_mode(struct iommu_option *cmd,
 			       struct iommufd_ctx *ictx);
 
+/*
+ * A HW pagetable is called an iommu_domain inside the kernel. This user object
+ * allows directly creating and inspecting the domains. Domains that have kernel
+ * owned page tables will be associated with an iommufd_ioas that provides the
+ * IOVA to PFN map.
+ */
+struct iommufd_hw_pagetable {
+	struct iommufd_object obj;
+	struct iommufd_ioas *ioas;
+	struct iommu_domain *domain;
+	bool auto_domain : 1;
+	/* Head at iommufd_ioas::hwpt_list */
+	struct list_head hwpt_item;
+	struct mutex devices_lock;
+	struct list_head devices;
+};
+
+struct iommufd_hw_pagetable *
+iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
+			   struct device *dev);
+void iommufd_hw_pagetable_destroy(struct iommufd_object *obj);
+
 struct iommufd_access {
 	unsigned long iova_alignment;
 	u32 iopt_access_list_id;
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 1c0a1f499378..ac6580a7b706 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -360,6 +360,9 @@ static const struct iommufd_object_ops iommufd_object_ops[] = {
 	[IOMMUFD_OBJ_IOAS] = {
 		.destroy = iommufd_ioas_destroy,
 	},
+	[IOMMUFD_OBJ_HW_PAGETABLE] = {
+		.destroy = iommufd_hw_pagetable_destroy,
+	},
 };
 
 static struct miscdevice iommu_misc_dev = {