[PATCH v6 10/19] iommufd: Allow a hwpt to be aborted after allocation

[Jason Gunthorpe <jgg@nvidia.com>]

During creation the hwpt must have the ioas->mutex held until the object
is finalized. This means we need to be able to call
iommufd_object_abort_and_destroy() while holding the mutex.

Since iommufd_hw_pagetable_destroy() also needs the mutex this is
problematic.

Fix it by creating a special abort op for the object that can assume the
caller is holding the lock, as required by the contract.

The next patch will add another iommufd_object_abort_and_destroy() for a
hwpt.

Fixes: e8d57210035b ("iommufd: Add kAPI toward external drivers for physical devices")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/iommufd/hw_pagetable.c    | 19 +++++++++++++++++++
 drivers/iommu/iommufd/iommufd_private.h |  1 +
 drivers/iommu/iommufd/main.c            |  7 ++++++-
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index e0699d7f4c64af..2087b51d9807ad 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -25,6 +25,21 @@ void iommufd_hw_pagetable_destroy(struct iommufd_object *obj)
 	refcount_dec(&hwpt->ioas->obj.users);
 }
 
+void iommufd_hw_pagetable_abort(struct iommufd_object *obj)
+{
+	struct iommufd_hw_pagetable *hwpt =
+		container_of(obj, struct iommufd_hw_pagetable, obj);
+
+	/* The ioas->mutex must be held until finalize is called. */
+	lockdep_assert_held(&hwpt->ioas->mutex);
+
+	if (!list_empty(&hwpt->hwpt_item)) {
+		list_del_init(&hwpt->hwpt_item);
+		iopt_table_remove_domain(&hwpt->ioas->iopt, hwpt->domain);
+	}
+	iommufd_hw_pagetable_destroy(obj);
+}
+
 int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt)
 {
 	if (hwpt->enforce_cache_coherency)
@@ -49,6 +64,10 @@ int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt)
  * Allocate a new iommu_domain and return it as a hw_pagetable. The HWPT
  * will be linked to the given ioas and upon return the underlying iommu_domain
  * is fully popoulated.
+ *
+ * The caller must hold the ioas->mutex until after
+ * iommufd_object_abort_and_destroy() or iommufd_object_finalize() is called on
+ * the returned hwpt.
  */
 struct iommufd_hw_pagetable *
 iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 471a3fdff1e0b6..a5d5a47641346f 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -260,6 +260,7 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 struct iommufd_hw_pagetable *
 iommufd_hw_pagetable_detach(struct iommufd_device *idev);
 void iommufd_hw_pagetable_destroy(struct iommufd_object *obj);
+void iommufd_hw_pagetable_abort(struct iommufd_object *obj);
 
 static inline void iommufd_hw_pagetable_put(struct iommufd_ctx *ictx,
 					    struct iommufd_hw_pagetable *hwpt)
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index e5ed5dfa91a0b5..24f30f384df6f9 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -24,6 +24,7 @@
 
 struct iommufd_object_ops {
 	void (*destroy)(struct iommufd_object *obj);
+	void (*abort)(struct iommufd_object *obj);
 };
 static const struct iommufd_object_ops iommufd_object_ops[];
 static struct miscdevice vfio_misc_dev;
@@ -95,7 +96,10 @@ void iommufd_object_abort(struct iommufd_ctx *ictx, struct iommufd_object *obj)
 void iommufd_object_abort_and_destroy(struct iommufd_ctx *ictx,
 				      struct iommufd_object *obj)
 {
-	iommufd_object_ops[obj->type].destroy(obj);
+	if (iommufd_object_ops[obj->type].abort)
+		iommufd_object_ops[obj->type].abort(obj);
+	else
+		iommufd_object_ops[obj->type].destroy(obj);
 	iommufd_object_abort(ictx, obj);
 }
 
@@ -401,6 +405,7 @@ static const struct iommufd_object_ops iommufd_object_ops[] = {
 	},
 	[IOMMUFD_OBJ_HW_PAGETABLE] = {
 		.destroy = iommufd_hw_pagetable_destroy,
+		.abort = iommufd_hw_pagetable_abort,
 	},
 #ifdef CONFIG_IOMMUFD_TEST
 	[IOMMUFD_OBJ_SELFTEST] = {
-- 
2.40.0