iommufd/viommu: Add IOMMU_VIOMMU_ALLOC ioctl

Add a new ioctl for user space to do a vIOMMU allocation. It must be based
on a nesting parent HWPT, so take its refcount.

IOMMU driver wanting to support vIOMMUs must define its IOMMU_VIOMMU_TYPE_
in the uAPI header and implement a viommu_alloc op in its iommu_ops.

Link: https://patch.msgid.link/r/dc2b8ba9ac935007beff07c1761c31cd097ed780.1730836219.git.nicolinc@nvidia.com
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommufd/Makefile

@@ -7,7 +7,8 @@ iommufd-y := \
 	ioas.o \
 	main.o \
 	pages.o \
-	vfio_compat.o
+	vfio_compat.o \
+	viommu.o
 
 iommufd-$(CONFIG_IOMMUFD_TEST) += selftest.o
 

drivers/iommu/iommufd/iommufd_private.h

@@ -506,6 +506,9 @@ static inline int iommufd_hwpt_replace_device(struct iommufd_device *idev,
 	return iommu_group_replace_domain(idev->igroup->group, hwpt->domain);
 }
 
+int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd);
+void iommufd_viommu_destroy(struct iommufd_object *obj);
+
 #ifdef CONFIG_IOMMUFD_TEST
 int iommufd_test(struct iommufd_ucmd *ucmd);
 void iommufd_selftest_destroy(struct iommufd_object *obj);

drivers/iommu/iommufd/main.c

@@ -307,6 +307,7 @@ union ucmd_buffer {
 	struct iommu_ioas_unmap unmap;
 	struct iommu_option option;
 	struct iommu_vfio_ioas vfio_ioas;
+	struct iommu_viommu_alloc viommu;
 #ifdef CONFIG_IOMMUFD_TEST
 	struct iommu_test_cmd test;
 #endif
@@ -360,6 +361,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
 		 val64),
 	IOCTL_OP(IOMMU_VFIO_IOAS, iommufd_vfio_ioas, struct iommu_vfio_ioas,
 		 __reserved),
+	IOCTL_OP(IOMMU_VIOMMU_ALLOC, iommufd_viommu_alloc_ioctl,
+		 struct iommu_viommu_alloc, out_viommu_id),
 #ifdef CONFIG_IOMMUFD_TEST
 	IOCTL_OP(IOMMU_TEST_CMD, iommufd_test, struct iommu_test_cmd, last),
 #endif
@@ -495,6 +498,9 @@ static const struct iommufd_object_ops iommufd_object_ops[] = {
 	[IOMMUFD_OBJ_FAULT] = {
 		.destroy = iommufd_fault_destroy,
 	},
+	[IOMMUFD_OBJ_VIOMMU] = {
+		.destroy = iommufd_viommu_destroy,
+	},
 #ifdef CONFIG_IOMMUFD_TEST
 	[IOMMUFD_OBJ_SELFTEST] = {
 		.destroy = iommufd_selftest_destroy,

drivers/iommu/iommufd/viommu.c

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES
+ */
+#include "iommufd_private.h"
+
+void iommufd_viommu_destroy(struct iommufd_object *obj)
+{
+	struct iommufd_viommu *viommu =
+		container_of(obj, struct iommufd_viommu, obj);
+
+	if (viommu->ops && viommu->ops->destroy)
+		viommu->ops->destroy(viommu);
+	refcount_dec(&viommu->hwpt->common.obj.users);
+}
+
+int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
+{
+	struct iommu_viommu_alloc *cmd = ucmd->cmd;
+	struct iommufd_hwpt_paging *hwpt_paging;
+	struct iommufd_viommu *viommu;
+	struct iommufd_device *idev;
+	const struct iommu_ops *ops;
+	int rc;
+
+	if (cmd->flags || cmd->type == IOMMU_VIOMMU_TYPE_DEFAULT)
+		return -EOPNOTSUPP;
+
+	idev = iommufd_get_device(ucmd, cmd->dev_id);
+	if (IS_ERR(idev))
+		return PTR_ERR(idev);
+
+	ops = dev_iommu_ops(idev->dev);
+	if (!ops->viommu_alloc) {
+		rc = -EOPNOTSUPP;
+		goto out_put_idev;
+	}
+
+	hwpt_paging = iommufd_get_hwpt_paging(ucmd, cmd->hwpt_id);
+	if (IS_ERR(hwpt_paging)) {
+		rc = PTR_ERR(hwpt_paging);
+		goto out_put_idev;
+	}
+
+	if (!hwpt_paging->nest_parent) {
+		rc = -EINVAL;
+		goto out_put_hwpt;
+	}
+
+	viommu = ops->viommu_alloc(idev->dev, hwpt_paging->common.domain,
+				   ucmd->ictx, cmd->type);
+	if (IS_ERR(viommu)) {
+		rc = PTR_ERR(viommu);
+		goto out_put_hwpt;
+	}
+
+	viommu->type = cmd->type;
+	viommu->ictx = ucmd->ictx;
+	viommu->hwpt = hwpt_paging;
+	refcount_inc(&viommu->hwpt->common.obj.users);
+	/*
+	 * It is the most likely case that a physical IOMMU is unpluggable. A
+	 * pluggable IOMMU instance (if exists) is responsible for refcounting
+	 * on its own.
+	 */
+	viommu->iommu_dev = __iommu_get_iommu_dev(idev->dev);
+
+	cmd->out_viommu_id = viommu->obj.id;
+	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
+	if (rc)
+		goto out_abort;
+	iommufd_object_finalize(ucmd->ictx, &viommu->obj);
+	goto out_put_hwpt;
+
+out_abort:
+	iommufd_object_abort_and_destroy(ucmd->ictx, &viommu->obj);
+out_put_hwpt:
+	iommufd_put_object(ucmd->ictx, &hwpt_paging->common.obj);
+out_put_idev:
+	iommufd_put_object(ucmd->ictx, &idev->obj);
+	return rc;
+}

include/uapi/linux/iommufd.h

@@ -52,6 +52,7 @@ enum {
 	IOMMUFD_CMD_HWPT_INVALIDATE = 0x8d,
 	IOMMUFD_CMD_FAULT_QUEUE_ALLOC = 0x8e,
 	IOMMUFD_CMD_IOAS_MAP_FILE = 0x8f,
+	IOMMUFD_CMD_VIOMMU_ALLOC = 0x90,
 };
 
 /**
@@ -822,4 +823,43 @@ struct iommu_fault_alloc {
 	__u32 out_fault_fd;
 };
 #define IOMMU_FAULT_QUEUE_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_FAULT_QUEUE_ALLOC)
+
+/**
+ * enum iommu_viommu_type - Virtual IOMMU Type
+ * @IOMMU_VIOMMU_TYPE_DEFAULT: Reserved for future use
+ */
+enum iommu_viommu_type {
+	IOMMU_VIOMMU_TYPE_DEFAULT = 0,
+};
+
+/**
+ * struct iommu_viommu_alloc - ioctl(IOMMU_VIOMMU_ALLOC)
+ * @size: sizeof(struct iommu_viommu_alloc)
+ * @flags: Must be 0
+ * @type: Type of the virtual IOMMU. Must be defined in enum iommu_viommu_type
+ * @dev_id: The device's physical IOMMU will be used to back the virtual IOMMU
+ * @hwpt_id: ID of a nesting parent HWPT to associate to
+ * @out_viommu_id: Output virtual IOMMU ID for the allocated object
+ *
+ * Allocate a virtual IOMMU object, representing the underlying physical IOMMU's
+ * virtualization support that is a security-isolated slice of the real IOMMU HW
+ * that is unique to a specific VM. Operations global to the IOMMU are connected
+ * to the vIOMMU, such as:
+ * - Security namespace for guest owned ID, e.g. guest-controlled cache tags
+ * - Non-device-affiliated event reporting, e.g. invalidation queue errors
+ * - Access to a sharable nesting parent pagetable across physical IOMMUs
+ * - Virtualization of various platforms IDs, e.g. RIDs and others
+ * - Delivery of paravirtualized invalidation
+ * - Direct assigned invalidation queues
+ * - Direct assigned interrupts
+ */
+struct iommu_viommu_alloc {
+	__u32 size;
+	__u32 flags;
+	__u32 type;
+	__u32 dev_id;
+	__u32 hwpt_id;
+	__u32 out_viommu_id;
+};
+#define IOMMU_VIOMMU_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_VIOMMU_ALLOC)
 #endif