[PATCH RFCv1 04/14] iommufd: Add struct iommufd_viommu and iommufd_viommu_ops

[Nicolin Chen]

Add a new iommufd_viommu core structure to represent a vIOMMU instance in
the user space, typically backed by a HW-accelerated feature of an IOMMU,
e.g. NVIDIA CMDQ-Virtualization (an ARM SMMUv3 extension) and AMD Hardware
Accelerated Virtualized IOMMU (vIOMMU).

Define a new iommufd_viommu_ops to hold the free op and any future op.

A driver should embed this core structure in its driver viommu structure
and call the new iommufd_viommu_alloc() helper to allocate a core/driver
structure bundle and fill its core viommu->ops:
    struct my_driver_viommu {
        struct iommufd_viommu core;
	....
    };

    static const struct iommufd_viommu_ops my_driver_viommu_ops = {
        .free = my_driver_viommu_free,
    };

    struct my_driver_viommu *my_viommu =
            iommufd_viommu_alloc(my_driver_viommu, core);
    my_viommu->core.ops = &my_driver_viommu_ops;

Lastly, add viommu_alloc to iommu_ops so iommufd can link to the driver to
allocate a viommu object.

Any future viommu op will be added to the new struct iommufd_viommu_ops.

Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
 drivers/iommu/iommufd/viommu.c |  2 ++
 include/linux/iommu.h          | 15 ++++++++++++++
 include/linux/iommufd.h        | 38 ++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/drivers/iommu/iommufd/viommu.c b/drivers/iommu/iommufd/viommu.c
index f77d6972d552..3886b1dd1f13 100644
--- a/drivers/iommu/iommufd/viommu.c
+++ b/drivers/iommu/iommufd/viommu.c
@@ -17,3 +17,5 @@
 			return NULL;                                           \
 		return container_of(obj, struct iommufd_##name, obj);          \
 	}
+
+viommu_struct_alloc(viommu);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 2e925b5eba53..4d4461146288 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -145,6 +145,8 @@ struct iopf_queue {
 	struct mutex lock;
 };
 
+struct iommufd_viommu;
+
 /* iommu fault flags */
 #define IOMMU_FAULT_READ	0x0
 #define IOMMU_FAULT_WRITE	0x1
@@ -527,6 +529,14 @@ static inline int __iommu_copy_struct_from_user_array(
  * @of_xlate: add OF master IDs to iommu grouping
  * @is_attach_deferred: Check if domain attach should be deferred from iommu
  *                      driver init to device driver init (default no)
+ * @viommu_alloc: Allocate an iommufd_viommu as a user space IOMMU instance,
+ *                associated to a nested parent @domain, for iommu-specific
+ *                hardware acceleration. The @viommu_type must be defined in
+ *                the include/uapi/linux/iommufd.h header.
+ *                It is suggested to call iommufd_viommu_alloc() helper for
+ *                a bundled allocation of the core and the driver structure,
+ *                and a driver in gernal should assign an iommufd_viommu_ops
+ *                to the core structure's viommu->ops.
  * @dev_enable/disable_feat: per device entries to enable/disable
  *                               iommu specific features.
  * @page_response: handle page request response
@@ -570,6 +580,11 @@ struct iommu_ops {
 	int (*of_xlate)(struct device *dev, const struct of_phandle_args *args);
 	bool (*is_attach_deferred)(struct device *dev);
 
+	/* User space instance allocation by the iommu driver */
+	struct iommufd_viommu *(*viommu_alloc)(struct device *dev,
+					       unsigned int viommu_type,
+					       struct iommu_domain *domain);
+
 	/* Per device IOMMU features */
 	int (*dev_enable_feat)(struct device *dev, enum iommu_dev_features f);
 	int (*dev_disable_feat)(struct device *dev, enum iommu_dev_features f);
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index a0cb08a4b653..650acfac307a 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -16,6 +16,7 @@ struct iommufd_device;
 struct page;
 struct iommufd_ctx;
 struct iommufd_access;
+struct iommufd_hwpt_paging;
 struct file;
 struct iommu_group;
 
@@ -77,6 +78,26 @@ void iommufd_access_detach(struct iommufd_access *access);
 
 void iommufd_ctx_get(struct iommufd_ctx *ictx);
 
+struct iommufd_viommu {
+	struct iommufd_object obj;
+	struct iommufd_ctx *ictx;
+	struct iommu_device *iommu_dev;
+	struct iommufd_hwpt_paging *hwpt;
+
+	const struct iommufd_viommu_ops *ops;
+
+	unsigned int type;
+};
+
+/**
+ * struct iommufd_viommu_ops - viommu specific operations
+ * @free: Free all driver-specific parts of an iommufd_viommu. The memory
+ *        of the entire viommu will be free-ed by iommufd core
+ */
+struct iommufd_viommu_ops {
+	void (*free)(struct iommufd_viommu *viommu);
+};
+
 #if IS_ENABLED(CONFIG_IOMMUFD)
 struct iommufd_ctx *iommufd_ctx_from_file(struct file *file);
 struct iommufd_ctx *iommufd_ctx_from_fd(int fd);
@@ -93,6 +114,8 @@ int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
 int iommufd_vfio_compat_ioas_get_id(struct iommufd_ctx *ictx, u32 *out_ioas_id);
 int iommufd_vfio_compat_ioas_create(struct iommufd_ctx *ictx);
 int iommufd_vfio_compat_set_no_iommu(struct iommufd_ctx *ictx);
+
+struct iommufd_viommu *_iommufd_viommu_alloc(size_t size);
 #else /* !CONFIG_IOMMUFD */
 static inline struct iommufd_ctx *iommufd_ctx_from_file(struct file *file)
 {
@@ -133,5 +156,20 @@ static inline int iommufd_vfio_compat_set_no_iommu(struct iommufd_ctx *ictx)
 {
 	return -EOPNOTSUPP;
 }
+
+static inline struct iommufd_viommu *_iommufd_viommu_alloc(size_t size)
+{
+	return NULL;
+}
 #endif /* CONFIG_IOMMUFD */
+
+/*
+ * Helpers for IOMMU driver to allocate driver structures that will be freed by
+ * the iommufd core. A driver is only responsible for its own struct cleanup.
+ */
+#define iommufd_viommu_alloc(drv_struct, member) \
+	container_of(_iommufd_viommu_alloc(sizeof(struct drv_struct) +        \
+					   BUILD_BUG_ON_ZERO(offsetof(        \
+						struct drv_struct, member))), \
+		     struct drv_struct, member)
 #endif
-- 
2.43.0