virt: acrn: Introduce ACRN HSM basic driver

ACRN Hypervisor Service Module (HSM) is a kernel module in Service VM
which communicates with ACRN userspace through ioctls and talks to ACRN
Hypervisor through hypercalls.

Add a basic HSM driver which allows Service VM userspace to communicate
with ACRN. The following patches will add more ioctls, guest VM memory
mapping caching, I/O request processing, ioeventfd and irqfd into this
module. HSM exports a char device interface (/dev/acrn_hsm) to userspace.

Cc: Dave Hansen <[e-mail]>
Cc: Zhi Wang <[e-mail]>
Cc: Zhenyu Wang <[e-mail]>
Cc: Yu Wang <[e-mail]>
Cc: Reinette Chatre <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Reviewed-by: Reinette Chatre <[e-mail]>
Signed-off-by: Shuo Liu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

MAINTAINERS

···
 S:	Supported
 W:	https://projectacrn.org
 F:	Documentation/virt/acrn/
+F:	drivers/virt/acrn/
 
 AD1889 ALSA SOUND DRIVER
 L:	[e-mail]

drivers/virt/Kconfig

···
 source "drivers/virt/vboxguest/Kconfig"
 
 source "drivers/virt/nitro_enclaves/Kconfig"
+
+source "drivers/virt/acrn/Kconfig"
 endif

drivers/virt/Makefile

···
 obj-y				+= vboxguest/
 
 obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
+obj-$(CONFIG_ACRN_HSM)		+= acrn/

drivers/virt/acrn/Kconfig

···
+# SPDX-License-Identifier: GPL-2.0
+config ACRN_HSM
+	tristate "ACRN Hypervisor Service Module"
+	depends on ACRN_GUEST
+	help
+	  ACRN Hypervisor Service Module (HSM) is a kernel module which
+	  communicates with ACRN userspace through ioctls and talks to
+	  the ACRN Hypervisor through hypercalls. HSM will only run in
+	  a privileged management VM, called Service VM, to manage User
+	  VMs and do I/O emulation. Not required for simply running
+	  under ACRN as a User VM.
+
+	  To compile as a module, choose M, the module will be called
+	  acrn. If unsure, say N.

drivers/virt/acrn/Makefile

···
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_ACRN_HSM)	:= acrn.o
+acrn-y := hsm.o

drivers/virt/acrn/acrn_drv.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ACRN_HSM_DRV_H
+#define __ACRN_HSM_DRV_H
+
+#include <linux/types.h>
+
+#define ACRN_INVALID_VMID (0xffffU)
+
+/**
+ * struct acrn_vm - Properties of ACRN User VM.
+ * @vmid:	User VM ID
+ */
+struct acrn_vm {
+	u16	vmid;
+};
+
+#endif /* __ACRN_HSM_DRV_H */

drivers/virt/acrn/hsm.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ACRN Hypervisor Service Module (HSM)
+ *
+ * Copyright (C) 2020 Intel Corporation. All rights reserved.
+ *
+ * Authors:
+ *	Fengwei Yin <[e-mail]>
+ *	Yakui Zhao <[e-mail]>
+ */
+
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#include <asm/acrn.h>
+#include <asm/hypervisor.h>
+
+#include "acrn_drv.h"
+
+/*
+ * When /dev/acrn_hsm is opened, a 'struct acrn_vm' object is created to
+ * represent a VM instance and continues to be associated with the opened file
+ * descriptor. All ioctl operations on this file descriptor will be targeted to
+ * the VM instance. Release of this file descriptor will destroy the object.
+ */
+static int acrn_dev_open(struct inode *inode, struct file *filp)
+{
+	struct acrn_vm *vm;
+
+	vm = kzalloc(sizeof(*vm), GFP_KERNEL);
+	if (!vm)
+		return -ENOMEM;
+
+	vm->vmid = ACRN_INVALID_VMID;
+	filp->private_data = vm;
+	return 0;
+}
+
+static int acrn_dev_release(struct inode *inode, struct file *filp)
+{
+	struct acrn_vm *vm = filp->private_data;
+
+	kfree(vm);
+	return 0;
+}
+
+static const struct file_operations acrn_fops = {
+	.owner		= THIS_MODULE,
+	.open		= acrn_dev_open,
+	.release	= acrn_dev_release,
+};
+
+static struct miscdevice acrn_dev = {
+	.minor	= MISC_DYNAMIC_MINOR,
+	.name	= "acrn_hsm",
+	.fops	= &acrn_fops,
+};
+
+static int __init hsm_init(void)
+{
+	int ret;
+
+	if (x86_hyper_type != X86_HYPER_ACRN)
+		return -ENODEV;
+
+	if (!(cpuid_eax(ACRN_CPUID_FEATURES) & ACRN_FEATURE_PRIVILEGED_VM))
+		return -EPERM;
+
+	ret = misc_register(&acrn_dev);
+	if (ret)
+		pr_err("Create misc dev failed!\n");
+
+	return ret;
+}
+
+static void __exit hsm_exit(void)
+{
+	misc_deregister(&acrn_dev);
+}
+module_init(hsm_init);
+module_exit(hsm_exit);
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("ACRN Hypervisor Service Module (HSM)");