The new HW queue object, as an internal iommufd object, wants to reuse the struct iommufd_access to pin some iova range in the iopt.
However, an access generally takes the refcount of an ictx. So, in such an internal case, a deadlock could happen when the release of the ictx has to wait for the release of the access first when releasing a hw_queue object, which could wait for the release of the ictx that is refcounted: ictx --releases--> hw_queue --releases--> access ^ | |_________________releases________________v
To address this, add a set of lightweight internal APIs to unlink the ictx and the access, i.e. no ictx refcounting by the access: ictx --releases--> hw_queue --releases--> access
Then, there's no point in setting the access->ictx. So simply define !ictx as an flag for an internal use and add an inline helper.
Signed-off-by: Nicolin Chen nicolinc@nvidia.com --- drivers/iommu/iommufd/iommufd_private.h | 23 ++++++++++ drivers/iommu/iommufd/device.c | 59 +++++++++++++++++++++---- 2 files changed, 73 insertions(+), 9 deletions(-)
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h index 09f895638f68..9d1f55deb9ca 100644 --- a/drivers/iommu/iommufd/iommufd_private.h +++ b/drivers/iommu/iommufd/iommufd_private.h @@ -484,6 +484,29 @@ void iopt_remove_access(struct io_pagetable *iopt, struct iommufd_access *access, u32 iopt_access_list_id); void iommufd_access_destroy_object(struct iommufd_object *obj);
+/* iommufd_access for internal use */ +static inline bool iommufd_access_is_internal(struct iommufd_access *access) +{ + return !access->ictx; +} + +struct iommufd_access *iommufd_access_create_internal(struct iommufd_ctx *ictx); + +static inline void +iommufd_access_destroy_internal(struct iommufd_ctx *ictx, + struct iommufd_access *access) +{ + iommufd_object_destroy_user(ictx, &access->obj); +} + +int iommufd_access_attach_internal(struct iommufd_access *access, + struct iommufd_ioas *ioas); + +static inline void iommufd_access_detach_internal(struct iommufd_access *access) +{ + iommufd_access_detach(access); +} + struct iommufd_eventq { struct iommufd_object obj; struct iommufd_ctx *ictx; diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c index e9b6ca47095c..07a4ff753c12 100644 --- a/drivers/iommu/iommufd/device.c +++ b/drivers/iommu/iommufd/device.c @@ -1084,7 +1084,39 @@ void iommufd_access_destroy_object(struct iommufd_object *obj) if (access->ioas) WARN_ON(iommufd_access_change_ioas(access, NULL)); mutex_unlock(&access->ioas_lock); - iommufd_ctx_put(access->ictx); + if (!iommufd_access_is_internal(access)) + iommufd_ctx_put(access->ictx); +} + +static struct iommufd_access *__iommufd_access_create(struct iommufd_ctx *ictx) +{ + struct iommufd_access *access; + + /* + * There is no uAPI for the access object, but to keep things symmetric + * use the object infrastructure anyhow. + */ + access = iommufd_object_alloc(ictx, access, IOMMUFD_OBJ_ACCESS); + if (IS_ERR(access)) + return access; + + /* The calling driver is a user until iommufd_access_destroy() */ + refcount_inc(&access->obj.users); + mutex_init(&access->ioas_lock); + return access; +} + +struct iommufd_access *iommufd_access_create_internal(struct iommufd_ctx *ictx) +{ + struct iommufd_access *access; + + access = __iommufd_access_create(ictx); + if (IS_ERR(access)) + return access; + access->iova_alignment = PAGE_SIZE; + + iommufd_object_finalize(ictx, &access->obj); + return access; }
/** @@ -1106,11 +1138,7 @@ iommufd_access_create(struct iommufd_ctx *ictx, { struct iommufd_access *access;
- /* - * There is no uAPI for the access object, but to keep things symmetric - * use the object infrastructure anyhow. - */ - access = iommufd_object_alloc(ictx, access, IOMMUFD_OBJ_ACCESS); + access = __iommufd_access_create(ictx); if (IS_ERR(access)) return access;
@@ -1122,13 +1150,10 @@ iommufd_access_create(struct iommufd_ctx *ictx, else access->iova_alignment = 1;
- /* The calling driver is a user until iommufd_access_destroy() */ - refcount_inc(&access->obj.users); access->ictx = ictx; iommufd_ctx_get(ictx); iommufd_object_finalize(ictx, &access->obj); *id = access->obj.id; - mutex_init(&access->ioas_lock); return access; } EXPORT_SYMBOL_NS_GPL(iommufd_access_create, "IOMMUFD"); @@ -1173,6 +1198,22 @@ int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id) } EXPORT_SYMBOL_NS_GPL(iommufd_access_attach, "IOMMUFD");
+int iommufd_access_attach_internal(struct iommufd_access *access, + struct iommufd_ioas *ioas) +{ + int rc; + + mutex_lock(&access->ioas_lock); + if (WARN_ON(access->ioas)) { + mutex_unlock(&access->ioas_lock); + return -EINVAL; + } + + rc = iommufd_access_change_ioas(access, ioas); + mutex_unlock(&access->ioas_lock); + return rc; +} + int iommufd_access_replace(struct iommufd_access *access, u32 ioas_id) { int rc;