From:   Elliot Berman <quic_eberman@quicinc.com>
To:     Alex Elder <elder@linaro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Elliot Berman <quic_eberman@quicinc.com>,
        Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>,
        Jonathan Corbet <corbet@lwn.net>
CC:     Murali Nalajala <quic_mnalajal@quicinc.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
        Carl van Schaik <quic_cvanscha@quicinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        "Konrad Dybcio" <konrad.dybcio@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        <linux-arm-msm@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-doc@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>
Subject: [PATCH v10 19/26] gunyah: vm_mgr: Add framework to add VM Functions
Date:   Tue, 14 Feb 2023 13:25:30 -0800
Message-ID: <20230214212531.3323284-1-quic_eberman@quicinc.com>
In-Reply-To: <20230214211229.3239350-1-quic_eberman@quicinc.com>
References: <20230214211229.3239350-1-quic_eberman@quicinc.com>
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Introduce a framework for Gunyah userspace to install VM functions. VM
functions are optional interfaces to the virtual machine. vCPUs,
ioeventfs, and irqfds are examples of such VM functions and are
implemented in subsequent patches.

A generic framework is implemented instead of individual ioctls to
create vCPUs, irqfds, etc., in order to simplify the VM manager core
implementation and allow dynamic loading of VM function modules.

Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
 Documentation/virt/gunyah/vm-manager.rst |  18 ++
 drivers/virt/gunyah/vm_mgr.c             | 240 ++++++++++++++++++++++-
 drivers/virt/gunyah/vm_mgr.h             |   3 +
 include/linux/gunyah_vm_mgr.h            |  80 ++++++++
 include/uapi/linux/gunyah.h              |  17 ++
 5 files changed, 353 insertions(+), 5 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 c0126cfeadc7..5272a6e9145c 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 fa324385ade5..e9c55e7dd1b3 100644
--- a/drivers/virt/gunyah/vm_mgr.c
+++ b/drivers/virt/gunyah/vm_mgr.c
@@ -6,8 +6,10 @@
 #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/mm.h>
 #include <linux/module.h>
@@ -16,6 +18,177 @@
 
 #include "vm_mgr.h"
 
+static DEFINE_MUTEX(functions_lock);
+static DEFINE_IDR(functions);
+
+int gh_vm_function_register(struct gh_vm_function *drv)
+{
+	int ret = 0;
+
+	if (!drv->bind || !drv->unbind)
+		return -EINVAL;
+
+	mutex_lock(&functions_lock);
+	if (idr_find(&functions, drv->type)) {
+		ret = -EEXIST;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&drv->instances);
+	ret = idr_alloc(&functions, drv, drv->type, drv->type + 1, GFP_KERNEL);
+	if (ret > 0)
+		ret = 0;
+out:
+	mutex_unlock(&functions_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gh_vm_function_register);
+
+static void gh_vm_remove_function_instance(struct gh_vm_function_instance *inst)
+	__must_hold(functions_lock)
+{
+	inst->fn->unbind(inst);
+	list_del(&inst->vm_list);
+	list_del(&inst->fn_list);
+	module_put(inst->fn->mod);
+	if (inst->arg_size)
+		kfree(inst->argp);
+	kfree(inst);
+}
+
+void gh_vm_function_unregister(struct gh_vm_function *fn)
+{
+	struct gh_vm_function_instance *inst, *iter;
+
+	mutex_lock(&functions_lock);
+	list_for_each_entry_safe(inst, iter, &fn->instances, fn_list)
+		gh_vm_remove_function_instance(inst);
+	idr_remove(&functions, fn->type);
+	mutex_unlock(&functions_lock);
+}
+EXPORT_SYMBOL_GPL(gh_vm_function_unregister);
+
+static long gh_vm_add_function(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)
+		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->arg) {
+			r = -ENOMEM;
+			goto free;
+		}
+
+		argp = is_compat_task() ? compat_ptr(f->arg) : (void __user *) f->arg;
+		if (copy_from_user(inst->argp, argp, f->arg_size)) {
+			r = -EFAULT;
+			goto free_arg;
+		}
+	} else {
+		inst->arg = f->arg;
+	}
+
+	mutex_lock(&functions_lock);
+	inst->fn = idr_find(&functions, f->type);
+	if (!inst->fn) {
+		mutex_unlock(&functions_lock);
+		r = request_module("ghfunc:%d", f->type);
+		if (r)
+			goto unlock_free;
+
+		mutex_lock(&functions_lock);
+		inst->fn = idr_find(&functions, f->type);
+	}
+
+	if (!inst->fn) {
+		r = -ENOENT;
+		goto unlock_free;
+	}
+
+	if (!try_module_get(inst->fn->mod)) {
+		r = -ENOENT;
+		inst->fn = NULL;
+		goto unlock_free;
+	}
+
+	inst->ghvm = ghvm;
+	inst->rm = ghvm->rm;
+
+	r = inst->fn->bind(inst);
+	if (r < 0) {
+		module_put(inst->fn->mod);
+		goto unlock_free;
+	}
+
+	list_add(&inst->vm_list, &ghvm->functions);
+	list_add(&inst->fn_list, &inst->fn->instances);
+	mutex_unlock(&functions_lock);
+	return r;
+unlock_free:
+	mutex_unlock(&functions_lock);
+free_arg:
+	if (inst->arg_size)
+		kfree(inst->argp);
+free:
+	kfree(inst);
+	return r;
+}
+
+static long gh_vm_rm_function(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(&functions_lock);
+	if (r)
+		return r;
+
+	if (f->arg_size) {
+		argp = kzalloc(f->arg_size, GFP_KERNEL);
+		if (!argp) {
+			r = -ENOMEM;
+			goto out;
+		}
+
+		user_argp = is_compat_task() ? compat_ptr(f->arg) : (void __user *) f->arg;
+		if (copy_from_user(argp, user_argp, f->arg_size)) {
+			r = -EFAULT;
+			kfree(argp);
+			goto out;
+		}
+
+		list_for_each_entry_safe(inst, iter, &ghvm->functions, vm_list) {
+			if (inst->fn->type == f->type &&
+				f->arg_size == inst->arg_size &&
+				!memcmp(argp, inst->argp, f->arg_size))
+				gh_vm_remove_function_instance(inst);
+		}
+	} else {
+		list_for_each_entry_safe(inst, iter, &ghvm->functions, vm_list) {
+			if (inst->fn->type == f->type &&
+				f->arg_size == inst->arg_size &&
+				inst->arg == f->arg)
+				gh_vm_remove_function_instance(inst);
+		}
+	}
+
+out:
+	mutex_unlock(&functions_lock);
+	return r;
+}
+
 static int gh_vm_rm_notification_status(struct gh_vm *ghvm, void *data)
 {
 	struct gh_rm_vm_status_payload *payload = data;
@@ -80,6 +253,7 @@ static void gh_vm_stop(struct gh_vm *ghvm)
 static void gh_vm_free(struct work_struct *work)
 {
 	struct gh_vm *ghvm = container_of(work, struct gh_vm, free_work);
+	struct gh_vm_function_instance *inst, *iiter;
 	struct gh_vm_mem *mapping, *tmp;
 	int ret;
 
@@ -90,7 +264,13 @@ static void gh_vm_free(struct work_struct *work)
 		fallthrough;
 	case GH_RM_VM_STATUS_INIT_FAILED:
 	case GH_RM_VM_STATUS_LOAD:
-	case GH_RM_VM_STATUS_LOAD_FAILED:
+	case GH_RM_VM_STATUS_EXITED:
+		mutex_lock(&functions_lock);
+		list_for_each_entry_safe(inst, iiter, &ghvm->functions, vm_list) {
+			gh_vm_remove_function_instance(inst);
+		}
+		mutex_unlock(&functions_lock);
+
 		mutex_lock(&ghvm->mm_lock);
 		list_for_each_entry_safe(mapping, tmp, &ghvm->memory_mappings, list) {
 			gh_vm_mem_reclaim(ghvm, mapping);
@@ -113,6 +293,28 @@ static void gh_vm_free(struct work_struct *work)
 	}
 }
 
+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);
+}
+
+int __must_check gh_vm_get(struct gh_vm *ghvm)
+{
+	return kref_get_unless_zero(&ghvm->kref);
+}
+EXPORT_SYMBOL_GPL(gh_vm_get);
+
+void gh_vm_put(struct gh_vm *ghvm)
+{
+	kref_put(&ghvm->kref, _gh_vm_put);
+}
+EXPORT_SYMBOL_GPL(gh_vm_put);
+
 static __must_check struct gh_vm *gh_vm_alloc(struct gh_rm *rm)
 {
 	struct gh_vm *ghvm;
@@ -147,6 +349,8 @@ static __must_check struct gh_vm *gh_vm_alloc(struct gh_rm *rm)
 	INIT_LIST_HEAD(&ghvm->memory_mappings);
 	init_rwsem(&ghvm->status_lock);
 	INIT_WORK(&ghvm->free_work, gh_vm_free);
+	kref_init(&ghvm->kref);
+	INIT_LIST_HEAD(&ghvm->functions);
 	ghvm->vm_status = GH_RM_VM_STATUS_LOAD;
 
 	return ghvm;
@@ -291,6 +495,35 @@ 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;
+
+		f = kzalloc(sizeof(*f), GFP_KERNEL);
+		if (!f)
+			return -ENOMEM;
+
+		if (copy_from_user(f, argp, sizeof(*f)))
+			return -EFAULT;
+
+		r = gh_vm_add_function(ghvm, f);
+		if (r < 0)
+			kfree(f);
+		break;
+	}
+	case GH_VM_REMOVE_FUNCTION: {
+		struct gh_fn_desc *f;
+
+		f = kzalloc(sizeof(*f), GFP_KERNEL);
+		if (!f)
+			return -ENOMEM;
+
+		if (copy_from_user(f, argp, sizeof(*f)))
+			return -EFAULT;
+
+		r = gh_vm_rm_function(ghvm, f);
+		kfree(f);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 		break;
@@ -303,10 +536,7 @@ static int gh_vm_release(struct inode *inode, struct file *filp)
 {
 	struct gh_vm *ghvm = filp->private_data;
 
-	/* 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);
+	gh_vm_put(ghvm);
 	return 0;
 }
 
diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
index e9cf56647cc2..4750d56c1297 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>
@@ -44,8 +45,10 @@ struct gh_vm {
 	struct rw_semaphore status_lock;
 
 	struct work_struct free_work;
+	struct kref kref;
 	struct mutex mm_lock;
 	struct list_head memory_mappings;
+	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 000000000000..f0a95af50b2e
--- /dev/null
+++ b/include/linux/gunyah_vm_mgr.h
@@ -0,0 +1,80 @@
+/* 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 {
+	u32 type;
+	const char *name;
+	struct module *mod;
+	long (*bind)(struct gh_vm_function_instance *f);
+	void (*unbind)(struct gh_vm_function_instance *f);
+	struct mutex instances_lock;
+	struct list_head instances;
+};
+
+/**
+ * struct gh_vm_function_instance - Represents one function instance
+ * @arg_size: size of user argument
+ * @arg: user argument to describe the function instance; arg_size is 0
+ * @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;
+	union {
+		u64 arg;
+		void *argp;
+	};
+	struct gh_vm *ghvm;
+	struct gh_rm *rm;
+	struct gh_vm_function *fn;
+	void *data;
+	struct list_head vm_list;
+	struct list_head fn_list;
+};
+
+int gh_vm_function_register(struct gh_vm_function *f);
+void gh_vm_function_unregister(struct gh_vm_function *f);
+
+#define DECLARE_GUNYAH_VM_FUNCTION(_name, _type, _bind, _unbind)	\
+	static struct gh_vm_function _name = {		\
+		.type = _type,						\
+		.name = __stringify(_name),				\
+		.mod = THIS_MODULE,					\
+		.bind = _bind,						\
+		.unbind = _unbind,					\
+	};								\
+	MODULE_ALIAS("ghfunc:"__stringify(_type))
+
+#define module_gunyah_vm_function(__gf)					\
+	module_driver(__gf, gh_vm_function_register, gh_vm_function_unregister)
+
+#define DECLARE_GUNYAH_VM_FUNCTION_INIT(_name, _type, _bind, _unbind)	\
+	DECLARE_GUNYAH_VM_FUNCTION(_name, _type, _bind, _unbind);	\
+	module_gunyah_vm_function(_name)
+
+#endif
diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index d899bba6a4c6..8df455a2a293 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h
@@ -66,4 +66,21 @@ 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 GH_FN_* macro for supported types
+ * @arg_size: Size of argument to pass to the function
+ * @arg: Value or pointer to argument given to the function
+ */
+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
-- 
2.39.1