Signed-off-by: Elliot Berman <redacted>
---
  Documentation/virt/gunyah/vm-manager.rst |  18 ++
  drivers/virt/gunyah/vm_mgr.c             | 213 ++++++++++++++++++++++-
  drivers/virt/gunyah/vm_mgr.h             |   4 +
  include/linux/gunyah_vm_mgr.h            |  97 +++++++++++
  include/uapi/linux/gunyah.h              |  18 ++
  5 files changed, 347 insertions(+), 3 deletions(-)
  create mode 100644 include/linux/gunyah_vm_mgr.h

diff --git a/Documentation/virt/gunyah/vm-manager.rst b/Documentation/virt/gunyah/vm-manager.rst
index df0e1a8279bf5..cbc79bd8749b4 100644
--- a/Documentation/virt/gunyah/vm-manager.rst
+++ b/Documentation/virt/gunyah/vm-manager.rst

@@ -15,6 +15,24 @@ such as vCPUs for the VM. Memory can be shared with the VM with
  `GH_VM_SET_USER_MEM_REGION`_. Userspace can interact with the resources in Linux
  by adding "functions" to the VM.
  
+Gunyah Functions
+================
+
+Components of a Gunyah VM's configuration that need kernel configuration are
+called "functions" and are built on top of a framework. Functions are identified
+by a string and have some argument(s) to configure them. They are typically
+created by the `GH_VM_ADD_FUNCTION`_ ioctl.

+   VM is starting.
+
+2. Register IO handler(s). IO handlers allow a function to handle stage-2 faults
+   from the virtual machine.
+
  Sample Userspace VMM
  ====================
  

diff --git a/drivers/virt/gunyah/vm_mgr.c b/drivers/virt/gunyah/vm_mgr.c
index 562ae6ed4a5f1..cfd79bc9900fd 100644
--- a/drivers/virt/gunyah/vm_mgr.c
+++ b/drivers/virt/gunyah/vm_mgr.c

@@ -6,10 +6,13 @@
  #define pr_fmt(fmt) "gh_vm_mgr: " fmt
  
  #include <linux/anon_inodes.h>
+#include <linux/compat.h>
  #include <linux/file.h>
  #include <linux/gunyah_rsc_mgr.h>
+#include <linux/gunyah_vm_mgr.h>
  #include <linux/miscdevice.h>
  #include <linux/module.h>
+#include <linux/xarray.h>
  
  #include <uapi/linux/gunyah.h>
  

@@ -17,6 +20,169 @@
  
  static void gh_vm_free(struct work_struct *work);
  
+static DEFINE_XARRAY(gh_vm_functions);
+
+static void gh_vm_put_function(struct gh_vm_function *fn)
+{
+	module_put(fn->mod);
+}
+
+static struct gh_vm_function *gh_vm_get_function(u32 type)
+{
+	struct gh_vm_function *fn;
+
+	fn = xa_load(&gh_vm_functions, type);
+	if (!fn) {
+		request_module("ghfunc:%d", type);
+
+		fn = xa_load(&gh_vm_functions, type);
+	}
+
+	if (!fn || !try_module_get(fn->mod))
+		fn = ERR_PTR(-ENOENT);
+
+	return fn;
+}
+
+static void gh_vm_remove_function_instance(struct gh_vm_function_instance *inst)
+	__must_hold(&inst->ghvm->fn_lock)
+{
+	inst->fn->unbind(inst);
+	list_del(&inst->vm_list);
+	gh_vm_put_function(inst->fn);
+	kfree(inst->argp);
+	kfree(inst);
+}
+
+static void gh_vm_remove_functions(struct gh_vm *ghvm)
+{
+	struct gh_vm_function_instance *inst, *iiter;
+
+	mutex_lock(&ghvm->fn_lock);
+	list_for_each_entry_safe(inst, iiter, &ghvm->functions, vm_list) {
+		gh_vm_remove_function_instance(inst);
+	}
+	mutex_unlock(&ghvm->fn_lock);
+}
+
+static long gh_vm_add_function_instance(struct gh_vm *ghvm, struct gh_fn_desc *f)
+{
+	struct gh_vm_function_instance *inst;
+	void __user *argp;
+	long r = 0;
+
+	if (f->arg_size > GH_FN_MAX_ARG_SIZE) {
+		dev_err_ratelimited(ghvm->parent, "%s: arg_size > %d\n",
+					__func__, GH_FN_MAX_ARG_SIZE);
+		return -EINVAL;
+	}
+
+	inst = kzalloc(sizeof(*inst), GFP_KERNEL);
+	if (!inst)
+		return -ENOMEM;
+
+	inst->arg_size = f->arg_size;
+	if (inst->arg_size) {
+		inst->argp = kzalloc(inst->arg_size, GFP_KERNEL);
+		if (!inst->argp) {
+			r = -ENOMEM;
+			goto free;
+		}
+
+		argp = u64_to_user_ptr(f->arg);
+		if (copy_from_user(inst->argp, argp, f->arg_size)) {
+			r = -EFAULT;
+			goto free_arg;
+		}
+	}
+
+	inst->fn = gh_vm_get_function(f->type);
+	if (IS_ERR(inst->fn)) {
+		r = PTR_ERR(inst->fn);
+		goto free_arg;
+	}
+
+	inst->ghvm = ghvm;
+	inst->rm = ghvm->rm;
+
+	mutex_lock(&ghvm->fn_lock);
+	r = inst->fn->bind(inst);
+	if (r < 0) {
+		mutex_unlock(&ghvm->fn_lock);
+		gh_vm_put_function(inst->fn);
+		goto free_arg;
+	}
+
+	list_add(&inst->vm_list, &ghvm->functions);
+	mutex_unlock(&ghvm->fn_lock);
+
+	return r;
+free_arg:
+	kfree(inst->argp);
+free:
+	kfree(inst);
+	return r;
+}
+
+static long gh_vm_rm_function_instance(struct gh_vm *ghvm, struct gh_fn_desc *f)
+{
+	struct gh_vm_function_instance *inst, *iter;
+	void __user *user_argp;
+	void *argp;
+	long r = 0;
+
+	r = mutex_lock_interruptible(&ghvm->fn_lock);
+	if (r)
+		return r;
+
+	if (f->arg_size) {
+		argp = kzalloc(f->arg_size, GFP_KERNEL);
+		if (!argp) {
+			r = -ENOMEM;
+			goto out;
+		}
+
+		user_argp = u64_to_user_ptr(f->arg);

+		if (copy_from_user(argp, user_argp, f->arg_size)) {
+			r = -EFAULT;
+			kfree(argp);
+			goto out;
+		}
+
+		r = -ENOENT;
+		list_for_each_entry_safe(inst, iter, &ghvm->functions, vm_list) {
+			if (inst->fn->type == f->type &&
+				inst->fn->compare(inst, argp, f->arg_size)) {
+				gh_vm_remove_function_instance(inst);
+				r = 0;
+			}
+		}
+
+		kfree(argp);
+	}
+
+out:
+	mutex_unlock(&ghvm->fn_lock);
+	return r;
+}
+
+int gh_vm_function_register(struct gh_vm_function *fn)
+{
+	if (!fn->bind || !fn->unbind)
+		return -EINVAL;
+
+	return xa_err(xa_store(&gh_vm_functions, fn->type, fn, GFP_KERNEL));
+}
+EXPORT_SYMBOL_GPL(gh_vm_function_register);
+
+void gh_vm_function_unregister(struct gh_vm_function *fn)
+{
+	/* Expecting unregister to only come when unloading a module */
+	WARN_ON(fn->mod && module_refcount(fn->mod));
+	xa_erase(&gh_vm_functions, fn->type);
+}
+EXPORT_SYMBOL_GPL(gh_vm_function_unregister);
+
  static int gh_vm_rm_notification_status(struct gh_vm *ghvm, void *data)
  {
  	struct gh_rm_vm_status_payload *payload = data;

@@ -98,6 +264,8 @@ static __must_check struct gh_vm *gh_vm_alloc(struct gh_rm *rm)
  	init_rwsem(&ghvm->status_lock);
  	init_waitqueue_head(&ghvm->vm_status_wait);
  	INIT_WORK(&ghvm->free_work, gh_vm_free);
+	kref_init(&ghvm->kref);
+	INIT_LIST_HEAD(&ghvm->functions);
  	ghvm->vm_status = GH_RM_VM_STATUS_NO_STATE;
  
  	return ghvm;

@@ -254,6 +422,24 @@ static long gh_vm_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
  		r = gh_vm_ensure_started(ghvm);
  		break;
  	}
+	case GH_VM_ADD_FUNCTION: {
+		struct gh_fn_desc f;
+
+		if (copy_from_user(&f, argp, sizeof(f)))
+			return -EFAULT;
+
+		r = gh_vm_add_function_instance(ghvm, &f);
+		break;
+	}
+	case GH_VM_REMOVE_FUNCTION: {
+		struct gh_fn_desc f;
+
+		if (copy_from_user(&f, argp, sizeof(f)))
+			return -EFAULT;
+
+		r = gh_vm_rm_function_instance(ghvm, &f);
+		break;
+	}
  	default:
  		r = -ENOTTY;
  		break;

@@ -270,6 +456,8 @@ static void gh_vm_free(struct work_struct *work)
  	if (ghvm->vm_status == GH_RM_VM_STATUS_RUNNING)
  		gh_vm_stop(ghvm);
  
+	gh_vm_remove_functions(ghvm);
+
  	if (ghvm->vm_status != GH_RM_VM_STATUS_NO_STATE &&
  	    ghvm->vm_status != GH_RM_VM_STATUS_LOAD &&
  	    ghvm->vm_status != GH_RM_VM_STATUS_RESET) {

@@ -294,14 +482,33 @@ static void gh_vm_free(struct work_struct *work)
  	kfree(ghvm);
  }
  
-static int gh_vm_release(struct inode *inode, struct file *filp)
+int __must_check gh_vm_get(struct gh_vm *ghvm)
  {
-	struct gh_vm *ghvm = filp->private_data;
+	return kref_get_unless_zero(&ghvm->kref);
+}
+EXPORT_SYMBOL_GPL(gh_vm_get);
+
+static void _gh_vm_put(struct kref *kref)
+{
+	struct gh_vm *ghvm = container_of(kref, struct gh_vm, kref);
  
  	/* VM will be reset and make RM calls which can interruptible sleep.
  	 * Defer to a work so this thread can receive signal.
  	 */
  	schedule_work(&ghvm->free_work);
+}
+
+void gh_vm_put(struct gh_vm *ghvm)
+{
+	kref_put(&ghvm->kref, _gh_vm_put);
+}
+EXPORT_SYMBOL_GPL(gh_vm_put);
+
+static int gh_vm_release(struct inode *inode, struct file *filp)
+{
+	struct gh_vm *ghvm = filp->private_data;
+
+	gh_vm_put(ghvm);
  	return 0;
  }
  

@@ -346,7 +553,7 @@ static long gh_dev_ioctl_create_vm(struct gh_rm *rm, unsigned long arg)
  err_put_fd:
  	put_unused_fd(fd);
  err_destroy_vm:
-	gh_vm_free(&ghvm->free_work);
+	gh_vm_put(ghvm);
  	return err;
  }
  

diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
index 4173bd51f83fe..c4bec1469ae8c 100644
--- a/drivers/virt/gunyah/vm_mgr.h
+++ b/drivers/virt/gunyah/vm_mgr.h

@@ -8,6 +8,7 @@
  
  #include <linux/gunyah_rsc_mgr.h>
  #include <linux/list.h>
+#include <linux/kref.h>
  #include <linux/miscdevice.h>
  #include <linux/mutex.h>
  #include <linux/rwsem.h>

@@ -45,9 +46,12 @@ struct gh_vm {
  	struct rw_semaphore status_lock;
  
  	struct work_struct free_work;
+	struct kref kref;
  	struct mm_struct *mm; /* userspace tied to this vm */
  	struct mutex mm_lock;
  	struct list_head memory_mappings;
+	struct mutex fn_lock;
+	struct list_head functions;
  };
  
  int gh_vm_mem_alloc(struct gh_vm *ghvm, struct gh_userspace_memory_region *region);

diff --git a/include/linux/gunyah_vm_mgr.h b/include/linux/gunyah_vm_mgr.h
new file mode 100644
index 0000000000000..6e4dd6fa5f96d
--- /dev/null
+++ b/include/linux/gunyah_vm_mgr.h

@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#ifndef _GUNYAH_VM_MGR_H
+#define _GUNYAH_VM_MGR_H
+
+#include <linux/compiler_types.h>
+#include <linux/gunyah.h>
+#include <linux/gunyah_rsc_mgr.h>
+#include <linux/list.h>
+#include <linux/mod_devicetable.h>
+#include <linux/notifier.h>
+
+#include <uapi/linux/gunyah.h>
+
+struct gh_vm;
+
+int __must_check gh_vm_get(struct gh_vm *ghvm);
+void gh_vm_put(struct gh_vm *ghvm);
+
+struct gh_vm_function_instance;
+/**
+ * struct gh_vm_function - Represents a function type
+ * @type: value from &enum gh_fn_type
+ * @name: friendly name for debug purposes
+ * @mod: owner of the function type
+ * @bind: Called when a new function of this type has been allocated.
+ * @unbind: Called when the function instance is being destroyed.
+ * @compare: Compare function instance @f's argument to the provided arg.
+ *           Return true if they are equivalent. Used on GH_VM_REMOVE_FUNCTION.
+ */
+struct gh_vm_function {
+	u32 type;
+	const char *name;
+	struct module *mod;
+	long (*bind)(struct gh_vm_function_instance *f);
+	void (*unbind)(struct gh_vm_function_instance *f);
+	bool (*compare)(const struct gh_vm_function_instance *f, const void *arg, size_t size);
+};
+
+/**
+ * struct gh_vm_function_instance - Represents one function instance
+ * @arg_size: size of user argument
+ * @argp: pointer to user argument
+ * @ghvm: Pointer to VM instance
+ * @rm: Pointer to resource manager for the VM instance
+ * @fn: The ops for the function
+ * @data: Private data for function
+ * @vm_list: for gh_vm's functions list
+ * @fn_list: for gh_vm_function's instances list
+ */
+struct gh_vm_function_instance {
+	size_t arg_size;
+	void *argp;
+	struct gh_vm *ghvm;
+	struct gh_rm *rm;
+	struct gh_vm_function *fn;
+	void *data;
+	struct list_head vm_list;
+};
+
+int gh_vm_function_register(struct gh_vm_function *f);
+void gh_vm_function_unregister(struct gh_vm_function *f);
+
+/* Since the function identifiers were setup in a uapi header as an
+ * enum and we do no want to change that, the user must supply the expanded
+ * constant as well and the compiler checks they are the same.
+ * See also MODULE_ALIAS_RDMA_NETLINK.
+ */
+#define MODULE_ALIAS_GH_VM_FUNCTION(_type, _idx)			\
+	static inline void __maybe_unused __chk##_idx(void)		\
+	{								\
+		BUILD_BUG_ON(_type != _idx);				\
+	}								\
+	MODULE_ALIAS("ghfunc:" __stringify(_idx))
+
+#define DECLARE_GH_VM_FUNCTION(_name, _type, _bind, _unbind, _compare)	\
+	static struct gh_vm_function _name = {				\
+		.type = _type,						\
+		.name = __stringify(_name),				\
+		.mod = THIS_MODULE,					\
+		.bind = _bind,						\
+		.unbind = _unbind,					\
+		.compare = _compare,					\
+	}
+
+#define module_gh_vm_function(__gf)					\
+	module_driver(__gf, gh_vm_function_register, gh_vm_function_unregister)
+
+#define DECLARE_GH_VM_FUNCTION_INIT(_name, _type, _idx, _bind, _unbind, _compare)	\
+	DECLARE_GH_VM_FUNCTION(_name, _type, _bind, _unbind, _compare);			\
+	module_gh_vm_function(_name);							\
+	MODULE_ALIAS_GH_VM_FUNCTION(_type, _idx)
+
+#endif

diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index 4b63d0b9b8ba7..bb07118a351fd 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h

@@ -72,4 +72,22 @@ struct gh_vm_dtb_config {
  
  #define GH_VM_START		_IO(GH_IOCTL_TYPE, 0x3)
  
+#define GH_FN_MAX_ARG_SIZE		256
+
+/**
+ * struct gh_fn_desc - Arguments to create a VM function
+ * @type: Type of the function. See &enum gh_fn_type.
+ * @arg_size: Size of argument to pass to the function. arg_size <= GH_FN_MAX_ARG_SIZE
+ * @arg: Pointer to argument given to the function. See &enum gh_fn_type for expected
+ *       arguments for a function type.
+ */
+struct gh_fn_desc {
+	__u32 type;
+	__u32 arg_size;
+	__u64 arg;
+};
+
+#define GH_VM_ADD_FUNCTION	_IOW(GH_IOCTL_TYPE, 0x4, struct gh_fn_desc)
+#define GH_VM_REMOVE_FUNCTION	_IOW(GH_IOCTL_TYPE, 0x7, struct gh_fn_desc)
+
  #endif