[v8,22/28] gunyah: vm_mgr: Add framework to add VM Functions

diff --git a/Documentation/virt/gunyah/vm-manager.rst b/Documentation/virt/gunyah/vm-manager.rst
index 62513af09cbf..d929f8f20b3b 100644
--- a/Documentation/virt/gunyah/vm-manager.rst
+++ b/Documentation/virt/gunyah/vm-manager.rst
@@ -17,6 +17,24 @@  sharing userspace memory with a VM is done via the GH_VM_SET_USER_MEM_REGION
 ioctl. The VM itself is configured to use the memory region via the
 devicetree.
 
+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.
+
+Functions typically will always do at least one of these operations:
+
+1. Create resource ticket(s). Resource tickets allow a function to register
+   itself as the client for a Gunyah resource (e.g. doorbell or vCPU) and
+   the function is given the pointer to the `struct gunyah_resource` when the
+   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 a96cb7f73754..a5bda4d6613b 100644
--- a/drivers/virt/gunyah/vm_mgr.c
+++ b/drivers/virt/gunyah/vm_mgr.c
@@ -15,6 +15,125 @@ 
 
 #include "vm_mgr.h"
 
+static DEFINE_MUTEX(functions_lock);
+static LIST_HEAD(functions);
+
+static struct gunyah_vm_function_driver *__find_function(const char name[GUNYAH_FUNCTION_NAME_SIZE])
+	__must_hold(functions_lock)
+{
+	struct gunyah_vm_function_driver *iter, *drv = NULL;
+
+	list_for_each_entry(iter, &functions, list) {
+		if (!strncmp(iter->name, name, GUNYAH_FUNCTION_NAME_SIZE)) {
+			drv = iter;
+			break;
+		}
+	}
+
+	return drv;
+}
+
+int gunyah_vm_function_register(struct gunyah_vm_function_driver *drv)
+{
+	int ret = 0;
+
+	mutex_lock(&functions_lock);
+	if (__find_function(drv->name)) {
+		ret = -EEXIST;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&drv->instances);
+	list_add(&drv->list, &functions);
+out:
+	mutex_unlock(&functions_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gunyah_vm_function_register);
+
+static void gh_vm_remove_function(struct gunyah_vm_function *f)
+	__must_hold(functions_lock)
+{
+	f->drv->release(f);
+	list_del(&f->vm_list);
+	list_del(&f->drv_list);
+	module_put(f->drv->mod);
+}
+
+void gunyah_vm_function_unregister(struct gunyah_vm_function_driver *drv)
+{
+	struct gunyah_vm_function *f, *iter;
+
+	mutex_lock(&functions_lock);
+	list_for_each_entry_safe(f, iter, &drv->instances, drv_list)
+		gh_vm_remove_function(f);
+	list_del(&drv->list);
+	mutex_unlock(&functions_lock);
+}
+EXPORT_SYMBOL_GPL(gunyah_vm_function_unregister);
+
+static long gh_vm_add_function(struct gunyah_vm *ghvm, struct gunyah_vm_function *f)
+{
+	long r = 0;
+
+	mutex_lock(&functions_lock);
+	f->drv = __find_function(f->fn.name);
+	if (!f->drv) {
+		mutex_unlock(&functions_lock);
+		r = request_module("ghfunc:%s", f->fn.name);
+		if (r)
+			return r;
+
+		mutex_lock(&functions_lock);
+		f->drv = __find_function(f->fn.name);
+	}
+
+	if (!f->drv) {
+		r = -ENOENT;
+		goto out;
+	}
+
+	if (!try_module_get(f->drv->mod)) {
+		r = -ENOENT;
+		f->drv = NULL;
+		goto out;
+	}
+
+	f->ghvm = ghvm;
+	f->rm = ghvm->rm;
+
+	r = f->drv->bind(f);
+	if (r < 0) {
+		module_put(f->drv->mod);
+		goto out;
+	}
+
+	list_add(&f->vm_list, &ghvm->functions);
+	list_add(&f->drv_list, &f->drv->instances);
+out:
+	mutex_unlock(&functions_lock);
+	return r;
+}
+
+static void ghvm_put(struct kref *kref)
+{
+	struct gunyah_vm *ghvm = container_of(kref, struct gunyah_vm, kref);
+
+	kfree(ghvm);
+}
+
+int __must_check get_gunyah_vm(struct gunyah_vm *ghvm)
+{
+	return kref_get_unless_zero(&ghvm->kref);
+}
+EXPORT_SYMBOL_GPL(get_gunyah_vm);
+
+void put_gunyah_vm(struct gunyah_vm *ghvm)
+{
+	kref_put(&ghvm->kref, ghvm_put);
+}
+EXPORT_SYMBOL_GPL(put_gunyah_vm);
+
 static __must_check struct gunyah_vm *gunyah_vm_alloc(struct gh_rm_rpc *rm)
 {
 	struct gunyah_vm *ghvm;
@@ -36,6 +155,8 @@  static __must_check struct gunyah_vm *gunyah_vm_alloc(struct gh_rm_rpc *rm)
 	mutex_init(&ghvm->mm_lock);
 	INIT_LIST_HEAD(&ghvm->memory_mappings);
 	init_rwsem(&ghvm->status_lock);
+	kref_init(&ghvm->kref);
+	INIT_LIST_HEAD(&ghvm->functions);
 
 	return ghvm;
 }
@@ -170,6 +291,23 @@  static long gh_vm_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			r = -EINVAL;
 		break;
 	}
+	case GH_VM_ADD_FUNCTION: {
+		struct gunyah_vm_function *f;
+
+		r = -ENOMEM;
+		f = kzalloc(sizeof(*f), GFP_KERNEL);
+		if (!f)
+			break;
+
+		r = -EFAULT;
+		if (copy_from_user(&f->fn, argp, sizeof(f->fn)))
+			break;
+
+		r = gh_vm_add_function(ghvm, f);
+		if (r < 0)
+			kfree(f);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 		break;
@@ -182,14 +320,19 @@  static int gh_vm_release(struct inode *inode, struct file *filp)
 {
 	struct gunyah_vm *ghvm = filp->private_data;
 	struct gunyah_vm_memory_mapping *mapping, *tmp;
+	struct gunyah_vm_function *f, *iter;
 
 	gh_vm_stop(ghvm);
 
+	list_for_each_entry_safe(f, iter, &ghvm->functions, vm_list) {
+		gh_vm_remove_function(f);
+	}
 	list_for_each_entry_safe(mapping, tmp, &ghvm->memory_mappings, list) {
 		gh_vm_mem_mapping_reclaim(ghvm, mapping);
 	}
+
 	put_gh_rm(ghvm->rm);
-	kfree(ghvm);
+	put_gunyah_vm(ghvm);
 	return 0;
 }
 
diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
index 8dcba9f14b5c..2c4fd240792a 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>
@@ -47,8 +48,12 @@  struct gunyah_vm {
 	enum gh_rm_vm_status vm_status;
 	struct rw_semaphore status_lock;
 
+	struct kref kref;
+
 	struct mutex mm_lock;
 	struct list_head memory_mappings;
+
+	struct list_head functions;
 };
 
 struct gunyah_vm_memory_mapping *gh_vm_mem_mapping_alloc(struct gunyah_vm *ghvm,
diff --git a/include/linux/gunyah_vm_mgr.h b/include/linux/gunyah_vm_mgr.h
new file mode 100644
index 000000000000..4bb06f100ae5
--- /dev/null
+++ b/include/linux/gunyah_vm_mgr.h
@@ -0,0 +1,68 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2022 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 gunyah_vm;
+
+int __must_check get_gunyah_vm(struct gunyah_vm *ghvm);
+void put_gunyah_vm(struct gunyah_vm *ghvm);
+
+struct gunyah_vm_function;
+struct gunyah_vm_function_driver {
+	const char name[GUNYAH_FUNCTION_NAME_SIZE];
+	struct module *mod;
+	long (*bind)(struct gunyah_vm_function *f);
+	void (*release)(struct gunyah_vm_function *f);
+	struct list_head list;
+	struct list_head instances;
+};
+
+struct gunyah_vm_function {
+	struct gh_vm_function fn;
+	struct gunyah_vm *ghvm;
+	struct gh_rm_rpc *rm;
+	struct gunyah_vm_function_driver *drv;
+	void *data;
+	struct list_head vm_list;
+	struct list_head drv_list;
+};
+
+int gunyah_vm_function_register(struct gunyah_vm_function_driver *f);
+void gunyah_vm_function_unregister(struct gunyah_vm_function_driver *f);
+
+#define DECLARE_GUNYAH_VM_FUNCTION(_name, _bind, _release)		\
+	static struct gunyah_vm_function_driver _name = {		\
+		.name = __stringify(_name),				\
+		.mod = THIS_MODULE,					\
+		.bind = _bind,						\
+		.release = _release,					\
+	};								\
+	MODULE_ALIAS("ghfunc:"__stringify(_name))
+
+#define DECLARE_GUNYAH_VM_FUNCTION_INIT(_name, _bind, _release)		\
+	DECLARE_GUNYAH_VM_FUNCTION(_name, _bind, _release);		\
+	static int __init _name##_mod_init(void)			\
+	{								\
+		return gunyah_vm_function_register(&(_name));		\
+	}								\
+	module_init(_name##_mod_init);					\
+	static void __exit _name##_mod_exit(void)			\
+	{								\
+		gunyah_vm_function_unregister(&(_name));		\
+	}								\
+	module_exit(_name##_mod_exit)
+
+#endif
diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index 36359ad2175e..40db32aeb012 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h
@@ -50,4 +50,16 @@  struct gh_vm_dtb_config {
 
 #define GH_VM_START		_IO(GH_IOCTL_TYPE, 0x3)
 
+#define GUNYAH_FUNCTION_NAME_SIZE		32
+#define GUNYAH_FUNCTION_MAX_ARG_SIZE		1024
+
+struct gh_vm_function {
+	char name[GUNYAH_FUNCTION_NAME_SIZE];
+	union {
+		char data[GUNYAH_FUNCTION_MAX_ARG_SIZE];
+	};
+};
+
+#define GH_VM_ADD_FUNCTION	_IOW(GH_IOCTL_TYPE, 0x4, struct gh_vm_function)
+
 #endif