// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2023, Microsoft Corporation.
 *
 * Author:
 *   Roman Kisel <romank@linux.microsoft.com>
 *   Saurabh Sengar <ssengar@linux.microsoft.com>
 *   Naman Jain <namjain@linux.microsoft.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/anon_inodes.h>
#include <linux/cpuhotplug.h>
#include <linux/count_zeros.h>
#include <linux/entry-virt.h>
#include <linux/eventfd.h>
#include <linux/poll.h>
#include <linux/file.h>
#include <linux/vmalloc.h>
#include <asm/debugreg.h>
#include <asm/mshyperv.h>
#include <trace/events/ipi.h>
#include <uapi/asm/mtrr.h>
#include <uapi/linux/mshv.h>
#include <hyperv/hvhdk.h>

#include "../../kernel/fpu/legacy.h"
#include "mshv.h"
#include "mshv_vtl.h"
#include "hyperv_vmbus.h"

MODULE_AUTHOR("Microsoft");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Microsoft Hyper-V VTL Driver");

#define MSHV_ENTRY_REASON_LOWER_VTL_CALL     0x1
#define MSHV_ENTRY_REASON_INTERRUPT          0x2
#define MSHV_ENTRY_REASON_INTERCEPT          0x3

#define MSHV_REAL_OFF_SHIFT	16
#define MSHV_PG_OFF_CPU_MASK	(BIT_ULL(MSHV_REAL_OFF_SHIFT) - 1)
#define MSHV_RUN_PAGE_OFFSET	0
#define MSHV_REG_PAGE_OFFSET	1
#define VTL2_VMBUS_SINT_INDEX	7

static struct device *mem_dev;

static struct tasklet_struct msg_dpc;
static wait_queue_head_t fd_wait_queue;
static bool has_message;
static struct eventfd_ctx *flag_eventfds[HV_EVENT_FLAGS_COUNT];
static DEFINE_MUTEX(flag_lock);
static bool __read_mostly mshv_has_reg_page;

/* hvcall code is of type u16, allocate a bitmap of size (1 << 16) to accommodate it */
#define MAX_BITMAP_SIZE ((U16_MAX + 1) / 8)

struct mshv_vtl_hvcall_fd {
	u8 allow_bitmap[MAX_BITMAP_SIZE];
	bool allow_map_initialized;
	/*
	 * Used to protect hvcall setup in IOCTLs
	 */
	struct mutex init_mutex;
	struct miscdevice *dev;
};

struct mshv_vtl_poll_file {
	struct file *file;
	wait_queue_entry_t wait;
	wait_queue_head_t *wqh;
	poll_table pt;
	int cpu;
};

struct mshv_vtl {
	struct device *module_dev;
	u64 id;
};

struct mshv_vtl_per_cpu {
	struct mshv_vtl_run *run;
	struct page *reg_page;
};

/* SYNIC_OVERLAY_PAGE_MSR - internal, identical to hv_synic_simp */
union hv_synic_overlay_page_msr {
	u64 as_uint64;
	struct {
		u64 enabled: 1;
		u64 reserved: 11;
		u64 pfn: 52;
	} __packed;
};

static struct mutex mshv_vtl_poll_file_lock;
static union hv_register_vsm_page_offsets mshv_vsm_page_offsets;
static union hv_register_vsm_capabilities mshv_vsm_capabilities;

static DEFINE_PER_CPU(struct mshv_vtl_poll_file, mshv_vtl_poll_file);
static DEFINE_PER_CPU(unsigned long long, num_vtl0_transitions);
static DEFINE_PER_CPU(struct mshv_vtl_per_cpu, mshv_vtl_per_cpu);

static const union hv_input_vtl input_vtl_zero;
static const union hv_input_vtl input_vtl_normal = {
	.use_target_vtl = 1,
};

static const struct file_operations mshv_vtl_fops;

static long
mshv_ioctl_create_vtl(void __user *user_arg, struct device *module_dev)
{
	struct mshv_vtl *vtl;
	struct file *file;
	int fd;

	vtl = kzalloc(sizeof(*vtl), GFP_KERNEL);
	if (!vtl)
		return -ENOMEM;

	fd = get_unused_fd_flags(O_CLOEXEC);
	if (fd < 0) {
		kfree(vtl);
		return fd;
	}
	file = anon_inode_getfile("mshv_vtl", &mshv_vtl_fops,
				  vtl, O_RDWR);
	if (IS_ERR(file)) {
		kfree(vtl);
		return PTR_ERR(file);
	}
	vtl->module_dev = module_dev;
	fd_install(fd, file);

	return fd;
}

static long
mshv_ioctl_check_extension(void __user *user_arg)
{
	u32 arg;

	if (copy_from_user(&arg, user_arg, sizeof(arg)))
		return -EFAULT;

	switch (arg) {
	case MSHV_CAP_CORE_API_STABLE:
		return 0;
	case MSHV_CAP_REGISTER_PAGE:
		return mshv_has_reg_page;
	case MSHV_CAP_VTL_RETURN_ACTION:
		return mshv_vsm_capabilities.return_action_available;
	case MSHV_CAP_DR6_SHARED:
		return mshv_vsm_capabilities.dr6_shared;
	}

	return -EOPNOTSUPP;
}

static long
mshv_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
{
	struct miscdevice *misc = filp->private_data;

	switch (ioctl) {
	case MSHV_CHECK_EXTENSION:
		return mshv_ioctl_check_extension((void __user *)arg);
	case MSHV_CREATE_VTL:
		return mshv_ioctl_create_vtl((void __user *)arg, misc->this_device);
	}

	return -ENOTTY;
}

static const struct file_operations mshv_dev_fops = {
	.owner		= THIS_MODULE,
	.unlocked_ioctl	= mshv_dev_ioctl,
	.llseek		= noop_llseek,
};

static struct miscdevice mshv_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "mshv",
	.fops = &mshv_dev_fops,
	.mode = 0600,
};

static struct mshv_vtl_run *mshv_vtl_this_run(void)
{
	return *this_cpu_ptr(&mshv_vtl_per_cpu.run);
}

static struct mshv_vtl_run *mshv_vtl_cpu_run(int cpu)
{
	return *per_cpu_ptr(&mshv_vtl_per_cpu.run, cpu);
}

static struct page *mshv_vtl_cpu_reg_page(int cpu)
{
	return *per_cpu_ptr(&mshv_vtl_per_cpu.reg_page, cpu);
}

static void mshv_vtl_configure_reg_page(struct mshv_vtl_per_cpu *per_cpu)
{
	struct hv_register_assoc reg_assoc = {};
	union hv_synic_overlay_page_msr overlay = {};
	struct page *reg_page;

	reg_page = alloc_page(GFP_KERNEL | __GFP_ZERO | __GFP_RETRY_MAYFAIL);
	if (!reg_page) {
		WARN(1, "failed to allocate register page\n");
		return;
	}

	overlay.enabled = 1;
	overlay.pfn = page_to_hvpfn(reg_page);
	reg_assoc.name = HV_X64_REGISTER_REG_PAGE;
	reg_assoc.value.reg64 = overlay.as_uint64;

	if (hv_call_set_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
				     1, input_vtl_zero, &reg_assoc)) {
		WARN(1, "failed to setup register page\n");
		__free_page(reg_page);
		return;
	}

	per_cpu->reg_page = reg_page;
	mshv_has_reg_page = true;
}

static void mshv_vtl_synic_enable_regs(unsigned int cpu)
{
	union hv_synic_sint sint;

	sint.as_uint64 = 0;
	sint.vector = HYPERVISOR_CALLBACK_VECTOR;
	sint.masked = false;
	sint.auto_eoi = hv_recommend_using_aeoi();

	/* Enable intercepts */
	if (!mshv_vsm_capabilities.intercept_page_available)
		hv_set_msr(HV_MSR_SINT0 + HV_SYNIC_INTERCEPTION_SINT_INDEX,
			   sint.as_uint64);

	/* VTL2 Host VSP SINT is (un)masked when the user mode requests that */
}

static int mshv_vtl_get_vsm_regs(void)
{
	struct hv_register_assoc registers[2];
	int ret, count = 2;

	registers[0].name = HV_REGISTER_VSM_CODE_PAGE_OFFSETS;
	registers[1].name = HV_REGISTER_VSM_CAPABILITIES;

	ret = hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
				       count, input_vtl_zero, registers);
	if (ret)
		return ret;

	mshv_vsm_page_offsets.as_uint64 = registers[0].value.reg64;
	mshv_vsm_capabilities.as_uint64 = registers[1].value.reg64;

	return ret;
}

static int mshv_vtl_configure_vsm_partition(struct device *dev)
{
	union hv_register_vsm_partition_config config;
	struct hv_register_assoc reg_assoc;

	config.as_uint64 = 0;
	config.default_vtl_protection_mask = HV_MAP_GPA_PERMISSIONS_MASK;
	config.enable_vtl_protection = 1;
	config.zero_memory_on_reset = 1;
	config.intercept_vp_startup = 1;
	config.intercept_cpuid_unimplemented = 1;

	if (mshv_vsm_capabilities.intercept_page_available) {
		dev_dbg(dev, "using intercept page\n");
		config.intercept_page = 1;
	}

	reg_assoc.name = HV_REGISTER_VSM_PARTITION_CONFIG;
	reg_assoc.value.reg64 = config.as_uint64;

	return hv_call_set_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
				       1, input_vtl_zero, &reg_assoc);
}

static void mshv_vtl_vmbus_isr(void)
{
	struct hv_per_cpu_context *per_cpu;
	struct hv_message *msg;
	u32 message_type;
	union hv_synic_event_flags *event_flags;
	struct eventfd_ctx *eventfd;
	u16 i;

	per_cpu = this_cpu_ptr(hv_context.cpu_context);
	if (smp_processor_id() == 0) {
		msg = (struct hv_message *)per_cpu->hyp_synic_message_page + VTL2_VMBUS_SINT_INDEX;
		message_type = READ_ONCE(msg->header.message_type);
		if (message_type != HVMSG_NONE)
			tasklet_schedule(&msg_dpc);
	}

	event_flags = (union hv_synic_event_flags *)per_cpu->hyp_synic_event_page +
			VTL2_VMBUS_SINT_INDEX;
	for_each_set_bit(i, event_flags->flags, HV_EVENT_FLAGS_COUNT) {
		if (!sync_test_and_clear_bit(i, event_flags->flags))
			continue;
		rcu_read_lock();
		eventfd = READ_ONCE(flag_eventfds[i]);
		if (eventfd)
			eventfd_signal(eventfd);
		rcu_read_unlock();
	}

	vmbus_isr();
}

static int mshv_vtl_alloc_context(unsigned int cpu)
{
	struct mshv_vtl_per_cpu *per_cpu = this_cpu_ptr(&mshv_vtl_per_cpu);

	per_cpu->run = (struct mshv_vtl_run *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
	if (!per_cpu->run)
		return -ENOMEM;

	if (mshv_vsm_capabilities.intercept_page_available)
		mshv_vtl_configure_reg_page(per_cpu);

	mshv_vtl_synic_enable_regs(cpu);

	return 0;
}

static int mshv_vtl_cpuhp_online;

static int hv_vtl_setup_synic(void)
{
	int ret;

	/* Use our isr to first filter out packets destined for userspace */
	hv_setup_vmbus_handler(mshv_vtl_vmbus_isr);

	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hyperv/vtl:online",
				mshv_vtl_alloc_context, NULL);
	if (ret < 0) {
		hv_setup_vmbus_handler(vmbus_isr);
		return ret;
	}

	mshv_vtl_cpuhp_online = ret;

	return 0;
}

static void hv_vtl_remove_synic(void)
{
	cpuhp_remove_state(mshv_vtl_cpuhp_online);
	hv_setup_vmbus_handler(vmbus_isr);
}

static int vtl_get_vp_register(struct hv_register_assoc *reg)
{
	return hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
					1, input_vtl_normal, reg);
}

static int vtl_set_vp_register(struct hv_register_assoc *reg)
{
	return hv_call_set_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
					1, input_vtl_normal, reg);
}

static int mshv_vtl_ioctl_add_vtl0_mem(struct mshv_vtl *vtl, void __user *arg)
{
	struct mshv_vtl_ram_disposition vtl0_mem;
	struct dev_pagemap *pgmap;
	void *addr;

	if (copy_from_user(&vtl0_mem, arg, sizeof(vtl0_mem)))
		return -EFAULT;
	/* vtl0_mem.last_pfn is excluded in the pagemap range for VTL0 as per design */
	if (vtl0_mem.last_pfn <= vtl0_mem.start_pfn) {
		dev_err(vtl->module_dev, "range start pfn (%llx) > end pfn (%llx)\n",
			vtl0_mem.start_pfn, vtl0_mem.last_pfn);
		return -EFAULT;
	}

	pgmap = kzalloc(sizeof(*pgmap), GFP_KERNEL);
	if (!pgmap)
		return -ENOMEM;

	pgmap->ranges[0].start = PFN_PHYS(vtl0_mem.start_pfn);
	pgmap->ranges[0].end = PFN_PHYS(vtl0_mem.last_pfn) - 1;
	pgmap->nr_range = 1;
	pgmap->type = MEMORY_DEVICE_GENERIC;

	/*
	 * Determine the highest page order that can be used for the given memory range.
	 * This works best when the range is aligned; i.e. both the start and the length.
	 */
	pgmap->vmemmap_shift = count_trailing_zeros(vtl0_mem.start_pfn | vtl0_mem.last_pfn);
	dev_dbg(vtl->module_dev,
		"Add VTL0 memory: start: 0x%llx, end_pfn: 0x%llx, page order: %lu\n",
		vtl0_mem.start_pfn, vtl0_mem.last_pfn, pgmap->vmemmap_shift);

	addr = devm_memremap_pages(mem_dev, pgmap);
	if (IS_ERR(addr)) {
		dev_err(vtl->module_dev, "devm_memremap_pages error: %ld\n", PTR_ERR(addr));
		kfree(pgmap);
		return -EFAULT;
	}

	/* Don't free pgmap, since it has to stick around until the memory
	 * is unmapped, which will never happen as there is no scenario
	 * where VTL0 can be released/shutdown without bringing down VTL2.
	 */
	return 0;
}

static void mshv_vtl_cancel(int cpu)
{
	int here = get_cpu();

	if (here != cpu) {
		if (!xchg_relaxed(&mshv_vtl_cpu_run(cpu)->cancel, 1))
			smp_send_reschedule(cpu);
	} else {
		WRITE_ONCE(mshv_vtl_this_run()->cancel, 1);
	}
	put_cpu();
}

static int mshv_vtl_poll_file_wake(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key)
{
	struct mshv_vtl_poll_file *poll_file = container_of(wait, struct mshv_vtl_poll_file, wait);

	mshv_vtl_cancel(poll_file->cpu);

	return 0;
}

static void mshv_vtl_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh, poll_table *pt)
{
	struct mshv_vtl_poll_file *poll_file = container_of(pt, struct mshv_vtl_poll_file, pt);

	WARN_ON(poll_file->wqh);
	poll_file->wqh = wqh;
	add_wait_queue(wqh, &poll_file->wait);
}

static int mshv_vtl_ioctl_set_poll_file(struct mshv_vtl_set_poll_file __user *user_input)
{
	struct file *file, *old_file;
	struct mshv_vtl_poll_file *poll_file;
	struct mshv_vtl_set_poll_file input;

	if (copy_from_user(&input, user_input, sizeof(input)))
		return -EFAULT;

	if (input.cpu >= num_possible_cpus() || !cpu_online(input.cpu))
		return -EINVAL;
	/*
	 * CPU Hotplug is not supported in VTL2 in OpenHCL, where this kernel driver exists.
	 * CPU is expected to remain online after above cpu_online() check.
	 */

	file = NULL;
	file = fget(input.fd);
	if (!file)
		return -EBADFD;

	poll_file = per_cpu_ptr(&mshv_vtl_poll_file, READ_ONCE(input.cpu));
	if (!poll_file)
		return -EINVAL;

	mutex_lock(&mshv_vtl_poll_file_lock);

	if (poll_file->wqh)
		remove_wait_queue(poll_file->wqh, &poll_file->wait);
	poll_file->wqh = NULL;

	old_file = poll_file->file;
	poll_file->file = file;
	poll_file->cpu = input.cpu;

	if (file) {
		init_waitqueue_func_entry(&poll_file->wait, mshv_vtl_poll_file_wake);
		init_poll_funcptr(&poll_file->pt, mshv_vtl_ptable_queue_proc);
		vfs_poll(file, &poll_file->pt);
	}

	mutex_unlock(&mshv_vtl_poll_file_lock);

	if (old_file)
		fput(old_file);

	return 0;
}

/* Static table mapping register names to their corresponding actions */
static const struct {
	enum hv_register_name reg_name;
	int debug_reg_num;  /* -1 if not a debug register */
	u32 msr_addr;       /* 0 if not an MSR */
} reg_table[] = {
	/* Debug registers */
	{HV_X64_REGISTER_DR0, 0, 0},
	{HV_X64_REGISTER_DR1, 1, 0},
	{HV_X64_REGISTER_DR2, 2, 0},
	{HV_X64_REGISTER_DR3, 3, 0},
	{HV_X64_REGISTER_DR6, 6, 0},
	/* MTRR MSRs */
	{HV_X64_REGISTER_MSR_MTRR_CAP, -1, MSR_MTRRcap},
	{HV_X64_REGISTER_MSR_MTRR_DEF_TYPE, -1, MSR_MTRRdefType},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE0, -1, MTRRphysBase_MSR(0)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE1, -1, MTRRphysBase_MSR(1)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE2, -1, MTRRphysBase_MSR(2)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE3, -1, MTRRphysBase_MSR(3)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE4, -1, MTRRphysBase_MSR(4)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE5, -1, MTRRphysBase_MSR(5)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE6, -1, MTRRphysBase_MSR(6)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE7, -1, MTRRphysBase_MSR(7)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE8, -1, MTRRphysBase_MSR(8)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASE9, -1, MTRRphysBase_MSR(9)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASEA, -1, MTRRphysBase_MSR(0xa)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASEB, -1, MTRRphysBase_MSR(0xb)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASEC, -1, MTRRphysBase_MSR(0xc)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASED, -1, MTRRphysBase_MSR(0xd)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASEE, -1, MTRRphysBase_MSR(0xe)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_BASEF, -1, MTRRphysBase_MSR(0xf)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK0, -1, MTRRphysMask_MSR(0)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK1, -1, MTRRphysMask_MSR(1)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK2, -1, MTRRphysMask_MSR(2)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK3, -1, MTRRphysMask_MSR(3)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK4, -1, MTRRphysMask_MSR(4)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK5, -1, MTRRphysMask_MSR(5)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK6, -1, MTRRphysMask_MSR(6)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK7, -1, MTRRphysMask_MSR(7)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK8, -1, MTRRphysMask_MSR(8)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASK9, -1, MTRRphysMask_MSR(9)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASKA, -1, MTRRphysMask_MSR(0xa)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASKB, -1, MTRRphysMask_MSR(0xb)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASKC, -1, MTRRphysMask_MSR(0xc)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASKD, -1, MTRRphysMask_MSR(0xd)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASKE, -1, MTRRphysMask_MSR(0xe)},
	{HV_X64_REGISTER_MSR_MTRR_PHYS_MASKF, -1, MTRRphysMask_MSR(0xf)},
	{HV_X64_REGISTER_MSR_MTRR_FIX64K00000, -1, MSR_MTRRfix64K_00000},
	{HV_X64_REGISTER_MSR_MTRR_FIX16K80000, -1, MSR_MTRRfix16K_80000},
	{HV_X64_REGISTER_MSR_MTRR_FIX16KA0000, -1, MSR_MTRRfix16K_A0000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KC0000, -1, MSR_MTRRfix4K_C0000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KC8000, -1, MSR_MTRRfix4K_C8000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KD0000, -1, MSR_MTRRfix4K_D0000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KD8000, -1, MSR_MTRRfix4K_D8000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KE0000, -1, MSR_MTRRfix4K_E0000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KE8000, -1, MSR_MTRRfix4K_E8000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KF0000, -1, MSR_MTRRfix4K_F0000},
	{HV_X64_REGISTER_MSR_MTRR_FIX4KF8000, -1, MSR_MTRRfix4K_F8000},
};

static int mshv_vtl_get_set_reg(struct hv_register_assoc *regs, bool set)
{
	u64 *reg64;
	enum hv_register_name gpr_name;
	int i;

	gpr_name = regs->name;
	reg64 = &regs->value.reg64;

	/* Search for the register in the table */
	for (i = 0; i < ARRAY_SIZE(reg_table); i++) {
		if (reg_table[i].reg_name != gpr_name)
			continue;
		if (reg_table[i].debug_reg_num != -1) {
			/* Handle debug registers */
			if (gpr_name == HV_X64_REGISTER_DR6 &&
			    !mshv_vsm_capabilities.dr6_shared)
				goto hypercall;
			if (set)
				native_set_debugreg(reg_table[i].debug_reg_num, *reg64);
			else
				*reg64 = native_get_debugreg(reg_table[i].debug_reg_num);
		} else {
			/* Handle MSRs */
			if (set)
				wrmsrl(reg_table[i].msr_addr, *reg64);
			else
				rdmsrl(reg_table[i].msr_addr, *reg64);
		}
		return 0;
	}

hypercall:
	return 1;
}

static void mshv_vtl_return(struct mshv_vtl_cpu_context *vtl0)
{
	struct hv_vp_assist_page *hvp;

	hvp = hv_vp_assist_page[smp_processor_id()];

	/*
	 * Process signal event direct set in the run page, if any.
	 */
	if (mshv_vsm_capabilities.return_action_available) {
		u32 offset = READ_ONCE(mshv_vtl_this_run()->vtl_ret_action_size);

		WRITE_ONCE(mshv_vtl_this_run()->vtl_ret_action_size, 0);

		/*
		 * Hypervisor will take care of clearing out the actions
		 * set in the assist page.
		 */
		memcpy(hvp->vtl_ret_actions,
		       mshv_vtl_this_run()->vtl_ret_actions,
		       min_t(u32, offset, sizeof(hvp->vtl_ret_actions)));
	}

	mshv_vtl_return_call(vtl0);
}

static bool mshv_vtl_process_intercept(void)
{
	struct hv_per_cpu_context *mshv_cpu;
	void *synic_message_page;
	struct hv_message *msg;
	u32 message_type;

	mshv_cpu = this_cpu_ptr(hv_context.cpu_context);
	synic_message_page = mshv_cpu->hyp_synic_message_page;
	if (unlikely(!synic_message_page))
		return true;

	msg = (struct hv_message *)synic_message_page + HV_SYNIC_INTERCEPTION_SINT_INDEX;
	message_type = READ_ONCE(msg->header.message_type);
	if (message_type == HVMSG_NONE)
		return true;

	memcpy(mshv_vtl_this_run()->exit_message, msg, sizeof(*msg));
	vmbus_signal_eom(msg, message_type);

	return false;
}

static int mshv_vtl_ioctl_return_to_lower_vtl(void)
{
	preempt_disable();
	for (;;) {
		unsigned long irq_flags;
		struct hv_vp_assist_page *hvp;
		int ret;

		if (__xfer_to_guest_mode_work_pending()) {
			preempt_enable();
			ret = xfer_to_guest_mode_handle_work();
			if (ret)
				return ret;
			preempt_disable();
		}

		local_irq_save(irq_flags);
		if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
			local_irq_restore(irq_flags);
			preempt_enable();
			return -EINTR;
		}

		mshv_vtl_return(&mshv_vtl_this_run()->cpu_context);
		local_irq_restore(irq_flags);

		hvp = hv_vp_assist_page[smp_processor_id()];
		this_cpu_inc(num_vtl0_transitions);
		switch (hvp->vtl_entry_reason) {
		case MSHV_ENTRY_REASON_INTERRUPT:
			if (!mshv_vsm_capabilities.intercept_page_available &&
			    likely(!mshv_vtl_process_intercept()))
				goto done;
			break;

		case MSHV_ENTRY_REASON_INTERCEPT:
			WARN_ON(!mshv_vsm_capabilities.intercept_page_available);
			memcpy(mshv_vtl_this_run()->exit_message, hvp->intercept_message,
			       sizeof(hvp->intercept_message));
			goto done;

		default:
			panic("unknown entry reason: %d", hvp->vtl_entry_reason);
		}
	}

done:
	preempt_enable();

	return 0;
}

static long
mshv_vtl_ioctl_get_regs(void __user *user_args)
{
	struct mshv_vp_registers args;
	struct hv_register_assoc reg;
	long ret;

	if (copy_from_user(&args, user_args, sizeof(args)))
		return -EFAULT;

	/*  This IOCTL supports processing only one register at a time. */
	if (args.count != 1)
		return -EINVAL;

	if (copy_from_user(&reg, (void __user *)args.regs_ptr,
			   sizeof(reg)))
		return -EFAULT;

	ret = mshv_vtl_get_set_reg(&reg, false);
	if (!ret)
		goto copy_args; /* No need of hypercall */
	ret = vtl_get_vp_register(&reg);
	if (ret)
		return ret;

copy_args:
	if (copy_to_user((void __user *)args.regs_ptr, &reg, sizeof(reg)))
		ret = -EFAULT;

	return ret;
}

static long
mshv_vtl_ioctl_set_regs(void __user *user_args)
{
	struct mshv_vp_registers args;
	struct hv_register_assoc reg;
	long ret;

	if (copy_from_user(&args, user_args, sizeof(args)))
		return -EFAULT;

	/*  This IOCTL supports processing only one register at a time. */
	if (args.count != 1)
		return -EINVAL;

	if (copy_from_user(&reg, (void __user *)args.regs_ptr, sizeof(reg)))
		return -EFAULT;

	ret = mshv_vtl_get_set_reg(&reg, true);
	if (!ret)
		return ret; /* No need of hypercall */
	ret = vtl_set_vp_register(&reg);

	return ret;
}

static long
mshv_vtl_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
{
	long ret;
	struct mshv_vtl *vtl = filp->private_data;

	switch (ioctl) {
	case MSHV_SET_POLL_FILE:
		ret = mshv_vtl_ioctl_set_poll_file((struct mshv_vtl_set_poll_file __user *)arg);
		break;
	case MSHV_GET_VP_REGISTERS:
		ret = mshv_vtl_ioctl_get_regs((void __user *)arg);
		break;
	case MSHV_SET_VP_REGISTERS:
		ret = mshv_vtl_ioctl_set_regs((void __user *)arg);
		break;
	case MSHV_RETURN_TO_LOWER_VTL:
		ret = mshv_vtl_ioctl_return_to_lower_vtl();
		break;
	case MSHV_ADD_VTL0_MEMORY:
		ret = mshv_vtl_ioctl_add_vtl0_mem(vtl, (void __user *)arg);
		break;
	default:
		dev_err(vtl->module_dev, "invalid vtl ioctl: %#x\n", ioctl);
		ret = -ENOTTY;
	}

	return ret;
}

static vm_fault_t mshv_vtl_fault(struct vm_fault *vmf)
{
	struct page *page;
	int cpu = vmf->pgoff & MSHV_PG_OFF_CPU_MASK;
	int real_off = vmf->pgoff >> MSHV_REAL_OFF_SHIFT;

	if (!cpu_online(cpu))
		return VM_FAULT_SIGBUS;
	/*
	 * CPU Hotplug is not supported in VTL2 in OpenHCL, where this kernel driver exists.
	 * CPU is expected to remain online after above cpu_online() check.
	 */

	if (real_off == MSHV_RUN_PAGE_OFFSET) {
		page = virt_to_page(mshv_vtl_cpu_run(cpu));
	} else if (real_off == MSHV_REG_PAGE_OFFSET) {
		if (!mshv_has_reg_page)
			return VM_FAULT_SIGBUS;
		page = mshv_vtl_cpu_reg_page(cpu);
	} else {
		return VM_FAULT_NOPAGE;
	}

	get_page(page);
	vmf->page = page;

	return 0;
}

static const struct vm_operations_struct mshv_vtl_vm_ops = {
	.fault = mshv_vtl_fault,
};

static int mshv_vtl_mmap(struct file *filp, struct vm_area_struct *vma)
{
	vma->vm_ops = &mshv_vtl_vm_ops;

	return 0;
}

static int mshv_vtl_release(struct inode *inode, struct file *filp)
{
	struct mshv_vtl *vtl = filp->private_data;

	kfree(vtl);

	return 0;
}

static const struct file_operations mshv_vtl_fops = {
	.owner = THIS_MODULE,
	.unlocked_ioctl = mshv_vtl_ioctl,
	.release = mshv_vtl_release,
	.mmap = mshv_vtl_mmap,
};

static void mshv_vtl_synic_mask_vmbus_sint(const u8 *mask)
{
	union hv_synic_sint sint;

	sint.as_uint64 = 0;
	sint.vector = HYPERVISOR_CALLBACK_VECTOR;
	sint.masked = (*mask != 0);
	sint.auto_eoi = hv_recommend_using_aeoi();

	hv_set_msr(HV_MSR_SINT0 + VTL2_VMBUS_SINT_INDEX,
		   sint.as_uint64);

	if (!sint.masked)
		pr_debug("%s: Unmasking VTL2 VMBUS SINT on VP %d\n", __func__, smp_processor_id());
	else
		pr_debug("%s: Masking VTL2 VMBUS SINT on VP %d\n", __func__, smp_processor_id());
}

static void mshv_vtl_read_remote(void *buffer)
{
	struct hv_per_cpu_context *mshv_cpu = this_cpu_ptr(hv_context.cpu_context);
	struct hv_message *msg = (struct hv_message *)mshv_cpu->hyp_synic_message_page +
					VTL2_VMBUS_SINT_INDEX;
	u32 message_type = READ_ONCE(msg->header.message_type);

	WRITE_ONCE(has_message, false);
	if (message_type == HVMSG_NONE)
		return;

	memcpy(buffer, msg, sizeof(*msg));
	vmbus_signal_eom(msg, message_type);
}

static bool vtl_synic_mask_vmbus_sint_masked = true;

static ssize_t mshv_vtl_sint_read(struct file *filp, char __user *arg, size_t size, loff_t *offset)
{
	struct hv_message msg = {};
	int ret;

	if (size < sizeof(msg))
		return -EINVAL;

	for (;;) {
		smp_call_function_single(VMBUS_CONNECT_CPU, mshv_vtl_read_remote, &msg, true);
		if (msg.header.message_type != HVMSG_NONE)
			break;

		if (READ_ONCE(vtl_synic_mask_vmbus_sint_masked))
			return 0; /* EOF */

		if (filp->f_flags & O_NONBLOCK)
			return -EAGAIN;

		ret = wait_event_interruptible(fd_wait_queue,
					       READ_ONCE(has_message) ||
						READ_ONCE(vtl_synic_mask_vmbus_sint_masked));
		if (ret)
			return ret;
	}

	if (copy_to_user(arg, &msg, sizeof(msg)))
		return -EFAULT;

	return sizeof(msg);
}

static __poll_t mshv_vtl_sint_poll(struct file *filp, poll_table *wait)
{
	__poll_t mask = 0;

	poll_wait(filp, &fd_wait_queue, wait);
	if (READ_ONCE(has_message) || READ_ONCE(vtl_synic_mask_vmbus_sint_masked))
		mask |= EPOLLIN | EPOLLRDNORM;

	return mask;
}

static void mshv_vtl_sint_on_msg_dpc(unsigned long data)
{
	WRITE_ONCE(has_message, true);
	wake_up_interruptible_poll(&fd_wait_queue, EPOLLIN);
}

static int mshv_vtl_sint_ioctl_post_msg(struct mshv_vtl_sint_post_msg __user *arg)
{
	struct mshv_vtl_sint_post_msg message;
	u8 payload[HV_MESSAGE_PAYLOAD_BYTE_COUNT];

	if (copy_from_user(&message, arg, sizeof(message)))
		return -EFAULT;
	if (message.payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
		return -EINVAL;
	if (copy_from_user(payload, (void __user *)message.payload_ptr,
			   message.payload_size))
		return -EFAULT;

	return hv_post_message((union hv_connection_id)message.connection_id,
			       message.message_type, (void *)payload,
			       message.payload_size);
}

static int mshv_vtl_sint_ioctl_signal_event(struct mshv_vtl_signal_event __user *arg)
{
	u64 input, status;
	struct mshv_vtl_signal_event signal_event;

	if (copy_from_user(&signal_event, arg, sizeof(signal_event)))
		return -EFAULT;

	input = signal_event.connection_id | ((u64)signal_event.flag << 32);

	status = hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, input);

	return hv_result_to_errno(status);
}

static int mshv_vtl_sint_ioctl_set_eventfd(struct mshv_vtl_set_eventfd __user *arg)
{
	struct mshv_vtl_set_eventfd set_eventfd;
	struct eventfd_ctx *eventfd, *old_eventfd;

	if (copy_from_user(&set_eventfd, arg, sizeof(set_eventfd)))
		return -EFAULT;
	if (set_eventfd.flag >= HV_EVENT_FLAGS_COUNT)
		return -EINVAL;

	eventfd = NULL;
	if (set_eventfd.fd >= 0) {
		eventfd = eventfd_ctx_fdget(set_eventfd.fd);
		if (IS_ERR(eventfd))
			return PTR_ERR(eventfd);
	}

	guard(mutex)(&flag_lock);
	old_eventfd = READ_ONCE(flag_eventfds[set_eventfd.flag]);
	WRITE_ONCE(flag_eventfds[set_eventfd.flag], eventfd);

	if (old_eventfd) {
		synchronize_rcu();
		eventfd_ctx_put(old_eventfd);
	}

	return 0;
}

static int mshv_vtl_sint_ioctl_pause_msg_stream(struct mshv_sint_mask __user *arg)
{
	static DEFINE_MUTEX(vtl2_vmbus_sint_mask_mutex);
	struct mshv_sint_mask mask;

	if (copy_from_user(&mask, arg, sizeof(mask)))
		return -EFAULT;
	guard(mutex)(&vtl2_vmbus_sint_mask_mutex);
	on_each_cpu((smp_call_func_t)mshv_vtl_synic_mask_vmbus_sint, &mask.mask, 1);
	WRITE_ONCE(vtl_synic_mask_vmbus_sint_masked, mask.mask != 0);
	if (mask.mask)
		wake_up_interruptible_poll(&fd_wait_queue, EPOLLIN);

	return 0;
}

static long mshv_vtl_sint_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
{
	switch (cmd) {
	case MSHV_SINT_POST_MESSAGE:
		return mshv_vtl_sint_ioctl_post_msg((struct mshv_vtl_sint_post_msg __user *)arg);
	case MSHV_SINT_SIGNAL_EVENT:
		return mshv_vtl_sint_ioctl_signal_event((struct mshv_vtl_signal_event __user *)arg);
	case MSHV_SINT_SET_EVENTFD:
		return mshv_vtl_sint_ioctl_set_eventfd((struct mshv_vtl_set_eventfd __user *)arg);
	case MSHV_SINT_PAUSE_MESSAGE_STREAM:
		return mshv_vtl_sint_ioctl_pause_msg_stream((struct mshv_sint_mask __user *)arg);
	default:
		return -ENOIOCTLCMD;
	}
}

static const struct file_operations mshv_vtl_sint_ops = {
	.owner = THIS_MODULE,
	.read = mshv_vtl_sint_read,
	.poll = mshv_vtl_sint_poll,
	.unlocked_ioctl = mshv_vtl_sint_ioctl,
};

static struct miscdevice mshv_vtl_sint_dev = {
	.name = "mshv_sint",
	.fops = &mshv_vtl_sint_ops,
	.mode = 0600,
	.minor = MISC_DYNAMIC_MINOR,
};

static int mshv_vtl_hvcall_dev_open(struct inode *node, struct file *f)
{
	struct miscdevice *dev = f->private_data;
	struct mshv_vtl_hvcall_fd *fd;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	fd = vzalloc(sizeof(*fd));
	if (!fd)
		return -ENOMEM;
	fd->dev = dev;
	f->private_data = fd;
	mutex_init(&fd->init_mutex);

	return 0;
}

static int mshv_vtl_hvcall_dev_release(struct inode *node, struct file *f)
{
	struct mshv_vtl_hvcall_fd *fd;

	fd = f->private_data;
	if (fd) {
		vfree(fd);
		f->private_data = NULL;
	}

	return 0;
}

static int mshv_vtl_hvcall_do_setup(struct mshv_vtl_hvcall_fd *fd,
				    struct mshv_vtl_hvcall_setup __user *hvcall_setup_user)
{
	struct mshv_vtl_hvcall_setup hvcall_setup;

	guard(mutex)(&fd->init_mutex);

	if (fd->allow_map_initialized) {
		dev_err(fd->dev->this_device,
			"Hypercall allow map has already been set, pid %d\n",
			current->pid);
		return -EINVAL;
	}

	if (copy_from_user(&hvcall_setup, hvcall_setup_user,
			   sizeof(struct mshv_vtl_hvcall_setup))) {
		return -EFAULT;
	}
	if (hvcall_setup.bitmap_array_size > ARRAY_SIZE(fd->allow_bitmap))
		return -EINVAL;

	if (copy_from_user(&fd->allow_bitmap,
			   (void __user *)hvcall_setup.allow_bitmap_ptr,
			   hvcall_setup.bitmap_array_size)) {
		return -EFAULT;
	}

	dev_info(fd->dev->this_device, "Hypercall allow map has been set, pid %d\n",
		 current->pid);
	fd->allow_map_initialized = true;
	return 0;
}

static bool mshv_vtl_hvcall_is_allowed(struct mshv_vtl_hvcall_fd *fd, u16 call_code)
{
	return test_bit(call_code, (unsigned long *)fd->allow_bitmap);
}

static int mshv_vtl_hvcall_call(struct mshv_vtl_hvcall_fd *fd,
				struct mshv_vtl_hvcall __user *hvcall_user)
{
	struct mshv_vtl_hvcall hvcall;
	void *in, *out;
	int ret;

	if (copy_from_user(&hvcall, hvcall_user, sizeof(struct mshv_vtl_hvcall)))
		return -EFAULT;
	if (hvcall.input_size > HV_HYP_PAGE_SIZE)
		return -EINVAL;
	if (hvcall.output_size > HV_HYP_PAGE_SIZE)
		return -EINVAL;

	/*
	 * By default, all hypercalls are not allowed.
	 * The user mode code has to set up the allow bitmap once.
	 */

	if (!mshv_vtl_hvcall_is_allowed(fd, hvcall.control & 0xFFFF)) {
		dev_err(fd->dev->this_device,
			"Hypercall with control data %#llx isn't allowed\n",
			hvcall.control);
		return -EPERM;
	}

	/*
	 * This may create a problem for Confidential VM (CVM) usecase where we need to use
	 * Hyper-V driver allocated per-cpu input and output pages (hyperv_pcpu_input_arg and
	 * hyperv_pcpu_output_arg) for making a hypervisor call.
	 *
	 * TODO: Take care of this when CVM support is added.
	 */
	in = (void *)__get_free_page(GFP_KERNEL);
	out = (void *)__get_free_page(GFP_KERNEL);

	if (copy_from_user(in, (void __user *)hvcall.input_ptr, hvcall.input_size)) {
		ret = -EFAULT;
		goto free_pages;
	}

	hvcall.status = hv_do_hypercall(hvcall.control, in, out);

	if (copy_to_user((void __user *)hvcall.output_ptr, out, hvcall.output_size)) {
		ret = -EFAULT;
		goto free_pages;
	}
	ret = put_user(hvcall.status, &hvcall_user->status);
free_pages:
	free_page((unsigned long)in);
	free_page((unsigned long)out);

	return ret;
}

static long mshv_vtl_hvcall_dev_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
{
	struct mshv_vtl_hvcall_fd *fd = f->private_data;

	switch (cmd) {
	case MSHV_HVCALL_SETUP:
		return mshv_vtl_hvcall_do_setup(fd, (struct mshv_vtl_hvcall_setup __user *)arg);
	case MSHV_HVCALL:
		return mshv_vtl_hvcall_call(fd, (struct mshv_vtl_hvcall __user *)arg);
	default:
		break;
	}

	return -ENOIOCTLCMD;
}

static const struct file_operations mshv_vtl_hvcall_dev_file_ops = {
	.owner = THIS_MODULE,
	.open = mshv_vtl_hvcall_dev_open,
	.release = mshv_vtl_hvcall_dev_release,
	.unlocked_ioctl = mshv_vtl_hvcall_dev_ioctl,
};

static struct miscdevice mshv_vtl_hvcall_dev = {
	.name = "mshv_hvcall",
	.nodename = "mshv_hvcall",
	.fops = &mshv_vtl_hvcall_dev_file_ops,
	.mode = 0600,
	.minor = MISC_DYNAMIC_MINOR,
};

static int mshv_vtl_low_open(struct inode *inodep, struct file *filp)
{
	pid_t pid = task_pid_vnr(current);
	uid_t uid = current_uid().val;
	int ret = 0;

	pr_debug("%s: Opening VTL low, task group %d, uid %d\n", __func__, pid, uid);

	if (capable(CAP_SYS_ADMIN)) {
		filp->private_data = inodep;
	} else {
		pr_err("%s: VTL low open failed: CAP_SYS_ADMIN required. task group %d, uid %d",
		       __func__, pid, uid);
		ret = -EPERM;
	}

	return ret;
}

static bool can_fault(struct vm_fault *vmf, unsigned long size, unsigned long *pfn)
{
	unsigned long mask = size - 1;
	unsigned long start = vmf->address & ~mask;
	unsigned long end = start + size;
	bool is_valid;

	is_valid = (vmf->address & mask) == ((vmf->pgoff << PAGE_SHIFT) & mask) &&
		start >= vmf->vma->vm_start &&
		end <= vmf->vma->vm_end;

	if (is_valid)
		*pfn = vmf->pgoff & ~(mask >> PAGE_SHIFT);

	return is_valid;
}

static vm_fault_t mshv_vtl_low_huge_fault(struct vm_fault *vmf, unsigned int order)
{
	unsigned long pfn = vmf->pgoff;
	vm_fault_t ret = VM_FAULT_FALLBACK;

	switch (order) {
	case 0:
		return vmf_insert_mixed(vmf->vma, vmf->address, pfn);

	case PMD_ORDER:
		if (can_fault(vmf, PMD_SIZE, &pfn))
			ret = vmf_insert_pfn_pmd(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
		return ret;

	case PUD_ORDER:
		if (can_fault(vmf, PUD_SIZE, &pfn))
			ret = vmf_insert_pfn_pud(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
		return ret;

	default:
		return VM_FAULT_SIGBUS;
	}
}

static vm_fault_t mshv_vtl_low_fault(struct vm_fault *vmf)
{
	return mshv_vtl_low_huge_fault(vmf, 0);
}

static const struct vm_operations_struct mshv_vtl_low_vm_ops = {
	.fault = mshv_vtl_low_fault,
	.huge_fault = mshv_vtl_low_huge_fault,
};

static int mshv_vtl_low_mmap(struct file *filp, struct vm_area_struct *vma)
{
	vma->vm_ops = &mshv_vtl_low_vm_ops;
	vm_flags_set(vma, VM_HUGEPAGE | VM_MIXEDMAP);

	return 0;
}

static const struct file_operations mshv_vtl_low_file_ops = {
	.owner		= THIS_MODULE,
	.open		= mshv_vtl_low_open,
	.mmap		= mshv_vtl_low_mmap,
};

static struct miscdevice mshv_vtl_low = {
	.name = "mshv_vtl_low",
	.nodename = "mshv_vtl_low",
	.fops = &mshv_vtl_low_file_ops,
	.mode = 0600,
	.minor = MISC_DYNAMIC_MINOR,
};

static int __init mshv_vtl_init(void)
{
	int ret;
	struct device *dev = mshv_dev.this_device;

	/*
	 * This creates /dev/mshv which provides functionality to create VTLs and partitions.
	 */
	ret = misc_register(&mshv_dev);
	if (ret) {
		dev_err(dev, "mshv device register failed: %d\n", ret);
		goto free_dev;
	}

	tasklet_init(&msg_dpc, mshv_vtl_sint_on_msg_dpc, 0);
	init_waitqueue_head(&fd_wait_queue);

	if (mshv_vtl_get_vsm_regs()) {
		dev_emerg(dev, "Unable to get VSM capabilities !!\n");
		ret = -ENODEV;
		goto free_dev;
	}
	if (mshv_vtl_configure_vsm_partition(dev)) {
		dev_emerg(dev, "VSM configuration failed !!\n");
		ret = -ENODEV;
		goto free_dev;
	}

	mshv_vtl_return_call_init(mshv_vsm_page_offsets.vtl_return_offset);
	ret = hv_vtl_setup_synic();
	if (ret)
		goto free_dev;

	/*
	 * mshv_sint device adds VMBus relay ioctl support.
	 * This provides a channel for VTL0 to communicate with VTL2.
	 */
	ret = misc_register(&mshv_vtl_sint_dev);
	if (ret)
		goto free_synic;

	/*
	 * mshv_hvcall device adds interface to enable userspace for direct hypercalls support.
	 */
	ret = misc_register(&mshv_vtl_hvcall_dev);
	if (ret)
		goto free_sint;

	/*
	 * mshv_vtl_low device is used to map VTL0 address space to a user-mode process in VTL2.
	 * It implements mmap() to allow a user-mode process in VTL2 to map to the address of VTL0.
	 */
	ret = misc_register(&mshv_vtl_low);
	if (ret)
		goto free_hvcall;

	/*
	 * "mshv vtl mem dev" device is later used to setup VTL0 memory.
	 */
	mem_dev = kzalloc(sizeof(*mem_dev), GFP_KERNEL);
	if (!mem_dev) {
		ret = -ENOMEM;
		goto free_low;
	}

	mutex_init(&mshv_vtl_poll_file_lock);

	device_initialize(mem_dev);
	dev_set_name(mem_dev, "mshv vtl mem dev");
	ret = device_add(mem_dev);
	if (ret) {
		dev_err(dev, "mshv vtl mem dev add: %d\n", ret);
		goto free_mem;
	}

	return 0;

free_mem:
	kfree(mem_dev);
free_low:
	misc_deregister(&mshv_vtl_low);
free_hvcall:
	misc_deregister(&mshv_vtl_hvcall_dev);
free_sint:
	misc_deregister(&mshv_vtl_sint_dev);
free_synic:
	hv_vtl_remove_synic();
free_dev:
	misc_deregister(&mshv_dev);

	return ret;
}

static void __exit mshv_vtl_exit(void)
{
	device_del(mem_dev);
	kfree(mem_dev);
	misc_deregister(&mshv_vtl_low);
	misc_deregister(&mshv_vtl_hvcall_dev);
	misc_deregister(&mshv_vtl_sint_dev);
	hv_vtl_remove_synic();
	misc_deregister(&mshv_dev);
}

module_init(mshv_vtl_init);
module_exit(mshv_vtl_exit);