drm/vmwgfx/vmwgfx_msg.c

// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
 * Copyright 2016 VMware, Inc., Palo Alto, CA., USA
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */

#include <linux/objtool.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/cc_platform.h>

#include <asm/hypervisor.h>
#include <drm/drm_ioctl.h>

#include "vmwgfx_drv.h"
#include "vmwgfx_msg_x86.h"
#include "vmwgfx_msg_arm64.h"
#include "vmwgfx_mksstat.h"

#define MESSAGE_STATUS_SUCCESS  0x0001
#define MESSAGE_STATUS_DORECV   0x0002
#define MESSAGE_STATUS_CPT      0x0010
#define MESSAGE_STATUS_HB       0x0080

#define RPCI_PROTOCOL_NUM       0x49435052
#define GUESTMSG_FLAG_COOKIE    0x80000000

#define RETRIES                 3

#define VMW_HYPERVISOR_MAGIC    0x564D5868

#define VMW_PORT_CMD_MSG        30
#define VMW_PORT_CMD_HB_MSG     0
#define VMW_PORT_CMD_OPEN_CHANNEL  (MSG_TYPE_OPEN << 16 | VMW_PORT_CMD_MSG)
#define VMW_PORT_CMD_CLOSE_CHANNEL (MSG_TYPE_CLOSE << 16 | VMW_PORT_CMD_MSG)
#define VMW_PORT_CMD_SENDSIZE   (MSG_TYPE_SENDSIZE << 16 | VMW_PORT_CMD_MSG)
#define VMW_PORT_CMD_RECVSIZE   (MSG_TYPE_RECVSIZE << 16 | VMW_PORT_CMD_MSG)
#define VMW_PORT_CMD_RECVSTATUS (MSG_TYPE_RECVSTATUS << 16 | VMW_PORT_CMD_MSG)

#define VMW_PORT_CMD_MKS_GUEST_STATS   85
#define VMW_PORT_CMD_MKSGS_RESET       (0 << 16 | VMW_PORT_CMD_MKS_GUEST_STATS)
#define VMW_PORT_CMD_MKSGS_ADD_PPN     (1 << 16 | VMW_PORT_CMD_MKS_GUEST_STATS)
#define VMW_PORT_CMD_MKSGS_REMOVE_PPN  (2 << 16 | VMW_PORT_CMD_MKS_GUEST_STATS)

#define HIGH_WORD(X) ((X & 0xFFFF0000) >> 16)

#define MAX_USER_MSG_LENGTH	PAGE_SIZE

static u32 vmw_msg_enabled = 1;

enum rpc_msg_type {
	MSG_TYPE_OPEN,
	MSG_TYPE_SENDSIZE,
	MSG_TYPE_SENDPAYLOAD,
	MSG_TYPE_RECVSIZE,
	MSG_TYPE_RECVPAYLOAD,
	MSG_TYPE_RECVSTATUS,
	MSG_TYPE_CLOSE,
};

struct rpc_channel {
	u16 channel_id;
	u32 cookie_high;
	u32 cookie_low;
};


/**
 * vmw_open_channel
 *
 * @channel: RPC channel
 * @protocol:
 *
 * Returns: 0 on success
 */
static int vmw_open_channel(struct rpc_channel *channel, unsigned int protocol)
{
	unsigned long eax, ebx, ecx, edx, si = 0, di = 0;

	VMW_PORT(VMW_PORT_CMD_OPEN_CHANNEL,
		(protocol | GUESTMSG_FLAG_COOKIE), si, di,
		0,
		VMW_HYPERVISOR_MAGIC,
		eax, ebx, ecx, edx, si, di);

	if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0)
		return -EINVAL;

	channel->channel_id  = HIGH_WORD(edx);
	channel->cookie_high = si;
	channel->cookie_low  = di;

	return 0;
}


/**
 * vmw_close_channel
 *
 * @channel: RPC channel
 *
 * Returns: 0 on success
 */
static int vmw_close_channel(struct rpc_channel *channel)
{
	unsigned long eax, ebx, ecx, edx, si, di;

	/* Set up additional parameters */
	si  = channel->cookie_high;
	di  = channel->cookie_low;

	VMW_PORT(VMW_PORT_CMD_CLOSE_CHANNEL,
		0, si, di,
		channel->channel_id << 16,
		VMW_HYPERVISOR_MAGIC,
		eax, ebx, ecx, edx, si, di);

	if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0)
		return -EINVAL;

	return 0;
}

/**
 * vmw_port_hb_out - Send the message payload either through the
 * high-bandwidth port if available, or through the backdoor otherwise.
 * @channel: The rpc channel.
 * @msg: NULL-terminated message.
 * @hb: Whether the high-bandwidth port is available.
 *
 * Return: The port status.
 */
static unsigned long vmw_port_hb_out(struct rpc_channel *channel,
				     const char *msg, bool hb)
{
	unsigned long si, di, eax, ebx, ecx, edx;
	unsigned long msg_len = strlen(msg);

	/* HB port can't access encrypted memory. */
	if (hb && !cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
		unsigned long bp = channel->cookie_high;
		u32 channel_id = (channel->channel_id << 16);

		si = (uintptr_t) msg;
		di = channel->cookie_low;

		VMW_PORT_HB_OUT(
			(MESSAGE_STATUS_SUCCESS << 16) | VMW_PORT_CMD_HB_MSG,
			msg_len, si, di,
			VMWARE_HYPERVISOR_HB | channel_id |
			VMWARE_HYPERVISOR_OUT,
			VMW_HYPERVISOR_MAGIC, bp,
			eax, ebx, ecx, edx, si, di);

		return ebx;
	}

	/* HB port not available. Send the message 4 bytes at a time. */
	ecx = MESSAGE_STATUS_SUCCESS << 16;
	while (msg_len && (HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS)) {
		unsigned int bytes = min_t(size_t, msg_len, 4);
		unsigned long word = 0;

		memcpy(&word, msg, bytes);
		msg_len -= bytes;
		msg += bytes;
		si = channel->cookie_high;
		di = channel->cookie_low;

		VMW_PORT(VMW_PORT_CMD_MSG | (MSG_TYPE_SENDPAYLOAD << 16),
			 word, si, di,
			 channel->channel_id << 16,
			 VMW_HYPERVISOR_MAGIC,
			 eax, ebx, ecx, edx, si, di);
	}

	return ecx;
}

/**
 * vmw_port_hb_in - Receive the message payload either through the
 * high-bandwidth port if available, or through the backdoor otherwise.
 * @channel: The rpc channel.
 * @reply: Pointer to buffer holding reply.
 * @reply_len: Length of the reply.
 * @hb: Whether the high-bandwidth port is available.
 *
 * Return: The port status.
 */
static unsigned long vmw_port_hb_in(struct rpc_channel *channel, char *reply,
				    unsigned long reply_len, bool hb)
{
	unsigned long si, di, eax, ebx, ecx, edx;

	/* HB port can't access encrypted memory */
	if (hb && !cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
		unsigned long bp = channel->cookie_low;
		u32 channel_id = (channel->channel_id << 16);

		si = channel->cookie_high;
		di = (uintptr_t) reply;

		VMW_PORT_HB_IN(
			(MESSAGE_STATUS_SUCCESS << 16) | VMW_PORT_CMD_HB_MSG,
			reply_len, si, di,
			VMWARE_HYPERVISOR_HB | channel_id,
			VMW_HYPERVISOR_MAGIC, bp,
			eax, ebx, ecx, edx, si, di);

		return ebx;
	}

	/* HB port not available. Retrieve the message 4 bytes at a time. */
	ecx = MESSAGE_STATUS_SUCCESS << 16;
	while (reply_len) {
		unsigned int bytes = min_t(unsigned long, reply_len, 4);

		si = channel->cookie_high;
		di = channel->cookie_low;

		VMW_PORT(VMW_PORT_CMD_MSG | (MSG_TYPE_RECVPAYLOAD << 16),
			 MESSAGE_STATUS_SUCCESS, si, di,
			 channel->channel_id << 16,
			 VMW_HYPERVISOR_MAGIC,
			 eax, ebx, ecx, edx, si, di);

		if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0)
			break;

		memcpy(reply, &ebx, bytes);
		reply_len -= bytes;
		reply += bytes;
	}

	return ecx;
}


/**
 * vmw_send_msg: Sends a message to the host
 *
 * @channel: RPC channel
 * @msg: NULL terminated string
 *
 * Returns: 0 on success
 */
static int vmw_send_msg(struct rpc_channel *channel, const char *msg)
{
	unsigned long eax, ebx, ecx, edx, si, di;
	size_t msg_len = strlen(msg);
	int retries = 0;

	while (retries < RETRIES) {
		retries++;

		/* Set up additional parameters */
		si  = channel->cookie_high;
		di  = channel->cookie_low;

		VMW_PORT(VMW_PORT_CMD_SENDSIZE,
			msg_len, si, di,
			channel->channel_id << 16,
			VMW_HYPERVISOR_MAGIC,
			eax, ebx, ecx, edx, si, di);

		if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0) {
			/* Expected success. Give up. */
			return -EINVAL;
		}

		/* Send msg */
		ebx = vmw_port_hb_out(channel, msg,
				      !!(HIGH_WORD(ecx) & MESSAGE_STATUS_HB));

		if ((HIGH_WORD(ebx) & MESSAGE_STATUS_SUCCESS) != 0) {
			return 0;
		} else if ((HIGH_WORD(ebx) & MESSAGE_STATUS_CPT) != 0) {
			/* A checkpoint occurred. Retry. */
			continue;
		} else {
			break;
		}
	}

	return -EINVAL;
}
STACK_FRAME_NON_STANDARD(vmw_send_msg);


/**
 * vmw_recv_msg: Receives a message from the host
 *
 * Note:  It is the caller's responsibility to call kfree() on msg.
 *
 * @channel:  channel opened by vmw_open_channel
 * @msg:  [OUT] message received from the host
 * @msg_len: message length
 */
static int vmw_recv_msg(struct rpc_channel *channel, void **msg,
			size_t *msg_len)
{
	unsigned long eax, ebx, ecx, edx, si, di;
	char *reply;
	size_t reply_len;
	int retries = 0;


	*msg_len = 0;
	*msg = NULL;

	while (retries < RETRIES) {
		retries++;

		/* Set up additional parameters */
		si  = channel->cookie_high;
		di  = channel->cookie_low;

		VMW_PORT(VMW_PORT_CMD_RECVSIZE,
			0, si, di,
			channel->channel_id << 16,
			VMW_HYPERVISOR_MAGIC,
			eax, ebx, ecx, edx, si, di);

		if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0) {
			DRM_ERROR("Failed to get reply size for host message.\n");
			return -EINVAL;
		}

		/* No reply available.  This is okay. */
		if ((HIGH_WORD(ecx) & MESSAGE_STATUS_DORECV) == 0)
			return 0;

		reply_len = ebx;
		reply     = kzalloc(reply_len + 1, GFP_KERNEL);
		if (!reply) {
			DRM_ERROR("Cannot allocate memory for host message reply.\n");
			return -ENOMEM;
		}


		/* Receive buffer */
		ebx = vmw_port_hb_in(channel, reply, reply_len,
				     !!(HIGH_WORD(ecx) & MESSAGE_STATUS_HB));
		if ((HIGH_WORD(ebx) & MESSAGE_STATUS_SUCCESS) == 0) {
			kfree(reply);
			reply = NULL;
			if ((HIGH_WORD(ebx) & MESSAGE_STATUS_CPT) != 0) {
				/* A checkpoint occurred. Retry. */
				continue;
			}

			return -EINVAL;
		}

		reply[reply_len] = '\0';


		/* Ack buffer */
		si  = channel->cookie_high;
		di  = channel->cookie_low;

		VMW_PORT(VMW_PORT_CMD_RECVSTATUS,
			MESSAGE_STATUS_SUCCESS, si, di,
			channel->channel_id << 16,
			VMW_HYPERVISOR_MAGIC,
			eax, ebx, ecx, edx, si, di);

		if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0) {
			kfree(reply);
			reply = NULL;
			if ((HIGH_WORD(ecx) & MESSAGE_STATUS_CPT) != 0) {
				/* A checkpoint occurred. Retry. */
				continue;
			}

			return -EINVAL;
		}

		break;
	}

	if (!reply)
		return -EINVAL;

	*msg_len = reply_len;
	*msg     = reply;

	return 0;
}
STACK_FRAME_NON_STANDARD(vmw_recv_msg);


/**
 * vmw_host_get_guestinfo: Gets a GuestInfo parameter
 *
 * Gets the value of a  GuestInfo.* parameter.  The value returned will be in
 * a string, and it is up to the caller to post-process.
 *
 * @guest_info_param:  Parameter to get, e.g. GuestInfo.svga.gl3
 * @buffer: if NULL, *reply_len will contain reply size.
 * @length: size of the reply_buf.  Set to size of reply upon return
 *
 * Returns: 0 on success
 */
int vmw_host_get_guestinfo(const char *guest_info_param,
			   char *buffer, size_t *length)
{
	struct rpc_channel channel;
	char *msg, *reply = NULL;
	size_t reply_len = 0;

	if (!vmw_msg_enabled)
		return -ENODEV;

	if (!guest_info_param || !length)
		return -EINVAL;

	msg = kasprintf(GFP_KERNEL, "info-get %s", guest_info_param);
	if (!msg) {
		DRM_ERROR("Cannot allocate memory to get guest info \"%s\".",
			  guest_info_param);
		return -ENOMEM;
	}

	if (vmw_open_channel(&channel, RPCI_PROTOCOL_NUM))
		goto out_open;

	if (vmw_send_msg(&channel, msg) ||
	    vmw_recv_msg(&channel, (void *) &reply, &reply_len))
		goto out_msg;

	vmw_close_channel(&channel);
	if (buffer && reply && reply_len > 0) {
		/* Remove reply code, which are the first 2 characters of
		 * the reply
		 */
		reply_len = max(reply_len - 2, (size_t) 0);
		reply_len = min(reply_len, *length);

		if (reply_len > 0)
			memcpy(buffer, reply + 2, reply_len);
	}

	*length = reply_len;

	kfree(reply);
	kfree(msg);

	return 0;

out_msg:
	vmw_close_channel(&channel);
	kfree(reply);
out_open:
	*length = 0;
	kfree(msg);
	DRM_ERROR("Failed to get guest info \"%s\".", guest_info_param);

	return -EINVAL;
}


/**
 * vmw_host_printf: Sends a log message to the host
 *
 * @fmt: Regular printf format string and arguments
 *
 * Returns: 0 on success
 */
__printf(1, 2)
int vmw_host_printf(const char *fmt, ...)
{
	va_list ap;
	struct rpc_channel channel;
	char *msg;
	char *log;
	int ret = 0;

	if (!vmw_msg_enabled)
		return -ENODEV;

	if (!fmt)
		return ret;

	va_start(ap, fmt);
	log = kvasprintf(GFP_KERNEL, fmt, ap);
	va_end(ap);
	if (!log) {
		DRM_ERROR("Cannot allocate memory for the log message.\n");
		return -ENOMEM;
	}

	msg = kasprintf(GFP_KERNEL, "log %s", log);
	if (!msg) {
		DRM_ERROR("Cannot allocate memory for host log message.\n");
		kfree(log);
		return -ENOMEM;
	}

	if (vmw_open_channel(&channel, RPCI_PROTOCOL_NUM))
		goto out_open;

	if (vmw_send_msg(&channel, msg))
		goto out_msg;

	vmw_close_channel(&channel);
	kfree(msg);
	kfree(log);

	return 0;

out_msg:
	vmw_close_channel(&channel);
out_open:
	kfree(msg);
	kfree(log);
	DRM_ERROR("Failed to send host log message.\n");

	return -EINVAL;
}


/**
 * vmw_msg_ioctl: Sends and receveives a message to/from host from/to user-space
 *
 * Sends a message from user-space to host.
 * Can also receive a result from host and return that to user-space.
 *
 * @dev: Identifies the drm device.
 * @data: Pointer to the ioctl argument.
 * @file_priv: Identifies the caller.
 * Return: Zero on success, negative error code on error.
 */

int vmw_msg_ioctl(struct drm_device *dev, void *data,
		  struct drm_file *file_priv)
{
	struct drm_vmw_msg_arg *arg =
			(struct drm_vmw_msg_arg *)data;
	struct rpc_channel channel;
	char *msg;
	int length;

	msg = kmalloc(MAX_USER_MSG_LENGTH, GFP_KERNEL);
	if (!msg) {
		DRM_ERROR("Cannot allocate memory for log message.\n");
		return -ENOMEM;
	}

	length = strncpy_from_user(msg, (void __user *)((unsigned long)arg->send),
				   MAX_USER_MSG_LENGTH);
	if (length < 0 || length >= MAX_USER_MSG_LENGTH) {
		DRM_ERROR("Userspace message access failure.\n");
		kfree(msg);
		return -EINVAL;
	}


	if (vmw_open_channel(&channel, RPCI_PROTOCOL_NUM)) {
		DRM_ERROR("Failed to open channel.\n");
		goto out_open;
	}

	if (vmw_send_msg(&channel, msg)) {
		DRM_ERROR("Failed to send message to host.\n");
		goto out_msg;
	}

	if (!arg->send_only) {
		char *reply = NULL;
		size_t reply_len = 0;

		if (vmw_recv_msg(&channel, (void *) &reply, &reply_len)) {
			DRM_ERROR("Failed to receive message from host.\n");
			goto out_msg;
		}
		if (reply && reply_len > 0) {
			if (copy_to_user((void __user *)((unsigned long)arg->receive),
					 reply, reply_len)) {
				DRM_ERROR("Failed to copy message to userspace.\n");
				kfree(reply);
				goto out_msg;
			}
			arg->receive_len = (__u32)reply_len;
		}
		kfree(reply);
	}

	vmw_close_channel(&channel);
	kfree(msg);

	return 0;

out_msg:
	vmw_close_channel(&channel);
out_open:
	kfree(msg);

	return -EINVAL;
}

/**
 * reset_ppn_array: Resets a PPN64 array to INVALID_PPN64 content
 *
 * @arr: Array to reset.
 * @size: Array length.
 */
static inline void reset_ppn_array(PPN64 *arr, size_t size)
{
	size_t i;

	BUG_ON(!arr || size == 0);

	for (i = 0; i < size; ++i)
		arr[i] = INVALID_PPN64;
}

/**
 * hypervisor_ppn_reset_all: Removes all mksGuestStat instance descriptors from
 * the hypervisor. All related pages should be subsequently unpinned or freed.
 *
 */
static inline void hypervisor_ppn_reset_all(void)
{
	unsigned long eax, ebx, ecx, edx, si = 0, di = 0;

	VMW_PORT(VMW_PORT_CMD_MKSGS_RESET,
		0, si, di,
		0,
		VMW_HYPERVISOR_MAGIC,
		eax, ebx, ecx, edx, si, di);
}

/**
 * hypervisor_ppn_add: Adds a single mksGuestStat instance descriptor to the
 * hypervisor. Any related userspace pages should be pinned in advance.
 *
 * @pfn: Physical page number of the instance descriptor
 */
static inline void hypervisor_ppn_add(PPN64 pfn)
{
	unsigned long eax, ebx, ecx, edx, si = 0, di = 0;

	VMW_PORT(VMW_PORT_CMD_MKSGS_ADD_PPN,
		(unsigned long)pfn, si, di,
		0,
		VMW_HYPERVISOR_MAGIC,
		eax, ebx, ecx, edx, si, di);
}

/**
 * hypervisor_ppn_remove: Removes a single mksGuestStat instance descriptor from
 * the hypervisor. All related pages should be subsequently unpinned or freed.
 *
 * @pfn: Physical page number of the instance descriptor
 */
static inline void hypervisor_ppn_remove(PPN64 pfn)
{
	unsigned long eax, ebx, ecx, edx, si = 0, di = 0;

	VMW_PORT(VMW_PORT_CMD_MKSGS_REMOVE_PPN,
		(unsigned long)pfn, si, di,
		0,
		VMW_HYPERVISOR_MAGIC,
		eax, ebx, ecx, edx, si, di);
}

#if IS_ENABLED(CONFIG_DRM_VMWGFX_MKSSTATS)

/* Order of the total number of pages used for kernel-internal mksGuestStat; at least 2 */
#define MKSSTAT_KERNEL_PAGES_ORDER 2
/* Header to the text description of mksGuestStat instance descriptor */
#define MKSSTAT_KERNEL_DESCRIPTION "vmwgfx"

/* Kernel mksGuestStats counter names and desciptions; same order as enum mksstat_kern_stats_t */
static const char* const mksstat_kern_name_desc[MKSSTAT_KERN_COUNT][2] =
{
	{ "vmw_execbuf_ioctl", "vmw_execbuf_ioctl" },
};

/**
 * mksstat_init_record: Initializes an MKSGuestStatCounter-based record
 * for the respective mksGuestStat index.
 *
 * @stat_idx: Index of the MKSGuestStatCounter-based mksGuestStat record.
 * @pstat: Pointer to array of MKSGuestStatCounterTime.
 * @pinfo: Pointer to array of MKSGuestStatInfoEntry.
 * @pstrs: Pointer to current end of the name/description sequence.
 * Return: Pointer to the new end of the names/description sequence.
 */

static inline char *mksstat_init_record(mksstat_kern_stats_t stat_idx,
	MKSGuestStatCounterTime *pstat, MKSGuestStatInfoEntry *pinfo, char *pstrs)
{
	char *const pstrd = pstrs + strlen(mksstat_kern_name_desc[stat_idx][0]) + 1;
	strcpy(pstrs, mksstat_kern_name_desc[stat_idx][0]);
	strcpy(pstrd, mksstat_kern_name_desc[stat_idx][1]);

	pinfo[stat_idx].name.s = pstrs;
	pinfo[stat_idx].description.s = pstrd;
	pinfo[stat_idx].flags = MKS_GUEST_STAT_FLAG_NONE;
	pinfo[stat_idx].stat.counter = (MKSGuestStatCounter *)&pstat[stat_idx];

	return pstrd + strlen(mksstat_kern_name_desc[stat_idx][1]) + 1;
}

/**
 * mksstat_init_record_time: Initializes an MKSGuestStatCounterTime-based record
 * for the respective mksGuestStat index.
 *
 * @stat_idx: Index of the MKSGuestStatCounterTime-based mksGuestStat record.
 * @pstat: Pointer to array of MKSGuestStatCounterTime.
 * @pinfo: Pointer to array of MKSGuestStatInfoEntry.
 * @pstrs: Pointer to current end of the name/description sequence.
 * Return: Pointer to the new end of the names/description sequence.
 */

static inline char *mksstat_init_record_time(mksstat_kern_stats_t stat_idx,
	MKSGuestStatCounterTime *pstat, MKSGuestStatInfoEntry *pinfo, char *pstrs)
{
	char *const pstrd = pstrs + strlen(mksstat_kern_name_desc[stat_idx][0]) + 1;
	strcpy(pstrs, mksstat_kern_name_desc[stat_idx][0]);
	strcpy(pstrd, mksstat_kern_name_desc[stat_idx][1]);

	pinfo[stat_idx].name.s = pstrs;
	pinfo[stat_idx].description.s = pstrd;
	pinfo[stat_idx].flags = MKS_GUEST_STAT_FLAG_TIME;
	pinfo[stat_idx].stat.counterTime = &pstat[stat_idx];

	return pstrd + strlen(mksstat_kern_name_desc[stat_idx][1]) + 1;
}

/**
 * mksstat_init_kern_id: Creates a single mksGuestStat instance descriptor and
 * kernel-internal counters. Adds PFN mapping to the hypervisor.
 *
 * Create a single mksGuestStat instance descriptor and corresponding structures
 * for all kernel-internal counters. The corresponding PFNs are mapped with the
 * hypervisor.
 *
 * @ppage: Output pointer to page containing the instance descriptor.
 * Return: Zero on success, negative error code on error.
 */

static int mksstat_init_kern_id(struct page **ppage)
{
	MKSGuestStatInstanceDescriptor *pdesc;
	MKSGuestStatCounterTime *pstat;
	MKSGuestStatInfoEntry *pinfo;
	char *pstrs, *pstrs_acc;

	/* Allocate pages for the kernel-internal instance descriptor */
	struct page *page = alloc_pages(GFP_KERNEL | __GFP_ZERO, MKSSTAT_KERNEL_PAGES_ORDER);

	if (!page)
		return -ENOMEM;

	pdesc = page_address(page);
	pstat = vmw_mksstat_get_kern_pstat(pdesc);
	pinfo = vmw_mksstat_get_kern_pinfo(pdesc);
	pstrs = vmw_mksstat_get_kern_pstrs(pdesc);

	/* Set up all kernel-internal counters and corresponding structures */
	pstrs_acc = pstrs;
	pstrs_acc = mksstat_init_record_time(MKSSTAT_KERN_EXECBUF, pstat, pinfo, pstrs_acc);

	/* Add new counters above, in their order of appearance in mksstat_kern_stats_t */

	BUG_ON(pstrs_acc - pstrs > PAGE_SIZE);

	/* Set up the kernel-internal instance descriptor */
	pdesc->reservedMBZ = 0;
	pdesc->statStartVA = (uintptr_t)pstat;
	pdesc->strsStartVA = (uintptr_t)pstrs;
	pdesc->statLength = sizeof(*pstat) * MKSSTAT_KERN_COUNT;
	pdesc->infoLength = sizeof(*pinfo) * MKSSTAT_KERN_COUNT;
	pdesc->strsLength = pstrs_acc - pstrs;
	snprintf(pdesc->description, ARRAY_SIZE(pdesc->description) - 1, "%s pid=%d",
		MKSSTAT_KERNEL_DESCRIPTION, current->pid);

	pdesc->statPPNs[0] = page_to_pfn(virt_to_page(pstat));
	reset_ppn_array(pdesc->statPPNs + 1, ARRAY_SIZE(pdesc->statPPNs) - 1);

	pdesc->infoPPNs[0] = page_to_pfn(virt_to_page(pinfo));
	reset_ppn_array(pdesc->infoPPNs + 1, ARRAY_SIZE(pdesc->infoPPNs) - 1);

	pdesc->strsPPNs[0] = page_to_pfn(virt_to_page(pstrs));
	reset_ppn_array(pdesc->strsPPNs + 1, ARRAY_SIZE(pdesc->strsPPNs) - 1);

	*ppage = page;

	hypervisor_ppn_add((PPN64)page_to_pfn(page));

	return 0;
}

/**
 * vmw_mksstat_get_kern_slot: Acquires a slot for a single kernel-internal
 * mksGuestStat instance descriptor.
 *
 * Find a slot for a single kernel-internal mksGuestStat instance descriptor.
 * In case no such was already present, allocate a new one and set up a kernel-
 * internal mksGuestStat instance descriptor for the former.
 *
 * @pid: Process for which a slot is sought.
 * @dev_priv: Identifies the drm private device.
 * Return: Non-negative slot on success, negative error code on error.
 */

int vmw_mksstat_get_kern_slot(pid_t pid, struct vmw_private *dev_priv)
{
	const size_t base = (u32)hash_32(pid, MKSSTAT_CAPACITY_LOG2);
	size_t i;

	for (i = 0; i < ARRAY_SIZE(dev_priv->mksstat_kern_pids); ++i) {
		const size_t slot = (i + base) % ARRAY_SIZE(dev_priv->mksstat_kern_pids);

		/* Check if an instance descriptor for this pid is already present */
		if (pid == (pid_t)atomic_read(&dev_priv->mksstat_kern_pids[slot]))
			return (int)slot;

		/* Set up a new instance descriptor for this pid */
		if (!atomic_cmpxchg(&dev_priv->mksstat_kern_pids[slot], 0, MKSSTAT_PID_RESERVED)) {
			const int ret = mksstat_init_kern_id(&dev_priv->mksstat_kern_pages[slot]);

			if (!ret) {
				/* Reset top-timer tracking for this slot */
				dev_priv->mksstat_kern_top_timer[slot] = MKSSTAT_KERN_COUNT;

				atomic_set(&dev_priv->mksstat_kern_pids[slot], pid);
				return (int)slot;
			}

			atomic_set(&dev_priv->mksstat_kern_pids[slot], 0);
			return ret;
		}
	}

	return -ENOSPC;
}

#endif

/**
 * vmw_mksstat_cleanup_descriptor: Frees a single userspace-originating
 * mksGuestStat instance-descriptor page and unpins all related user pages.
 *
 * Unpin all user pages realated to this instance descriptor and free
 * the instance-descriptor page itself.
 *
 * @page: Page of the instance descriptor.
 */

static void vmw_mksstat_cleanup_descriptor(struct page *page)
{
	MKSGuestStatInstanceDescriptor *pdesc = page_address(page);
	size_t i;

	for (i = 0; i < ARRAY_SIZE(pdesc->statPPNs) && pdesc->statPPNs[i] != INVALID_PPN64; ++i)
		unpin_user_page(pfn_to_page(pdesc->statPPNs[i]));

	for (i = 0; i < ARRAY_SIZE(pdesc->infoPPNs) && pdesc->infoPPNs[i] != INVALID_PPN64; ++i)
		unpin_user_page(pfn_to_page(pdesc->infoPPNs[i]));

	for (i = 0; i < ARRAY_SIZE(pdesc->strsPPNs) && pdesc->strsPPNs[i] != INVALID_PPN64; ++i)
		unpin_user_page(pfn_to_page(pdesc->strsPPNs[i]));

	__free_page(page);
}

/**
 * vmw_mksstat_remove_all: Resets all mksGuestStat instance descriptors
 * from the hypervisor.
 *
 * Discard all hypervisor PFN mappings, containing active mksGuestState instance
 * descriptors, unpin the related userspace pages and free the related kernel pages.
 *
 * @dev_priv: Identifies the drm private device.
 * Return: Zero on success, negative error code on error.
 */

int vmw_mksstat_remove_all(struct vmw_private *dev_priv)
{
	int ret = 0;
	size_t i;

	/* Discard all PFN mappings with the hypervisor */
	hypervisor_ppn_reset_all();

	/* Discard all userspace-originating instance descriptors and unpin all related pages */
	for (i = 0; i < ARRAY_SIZE(dev_priv->mksstat_user_pids); ++i) {
		const pid_t pid0 = (pid_t)atomic_read(&dev_priv->mksstat_user_pids[i]);

		if (!pid0)
			continue;

		if (pid0 != MKSSTAT_PID_RESERVED) {
			const pid_t pid1 = atomic_cmpxchg(&dev_priv->mksstat_user_pids[i], pid0, MKSSTAT_PID_RESERVED);

			if (!pid1)
				continue;

			if (pid1 == pid0) {
				struct page *const page = dev_priv->mksstat_user_pages[i];

				BUG_ON(!page);

				dev_priv->mksstat_user_pages[i] = NULL;
				atomic_set(&dev_priv->mksstat_user_pids[i], 0);

				vmw_mksstat_cleanup_descriptor(page);
				continue;
			}
		}

		ret = -EAGAIN;
	}

#if IS_ENABLED(CONFIG_DRM_VMWGFX_MKSSTATS)
	/* Discard all kernel-internal instance descriptors and free all related pages */
	for (i = 0; i < ARRAY_SIZE(dev_priv->mksstat_kern_pids); ++i) {
		const pid_t pid0 = (pid_t)atomic_read(&dev_priv->mksstat_kern_pids[i]);

		if (!pid0)
			continue;

		if (pid0 != MKSSTAT_PID_RESERVED) {
			const pid_t pid1 = atomic_cmpxchg(&dev_priv->mksstat_kern_pids[i], pid0, MKSSTAT_PID_RESERVED);

			if (!pid1)
				continue;

			if (pid1 == pid0) {
				struct page *const page = dev_priv->mksstat_kern_pages[i];

				BUG_ON(!page);

				dev_priv->mksstat_kern_pages[i] = NULL;
				atomic_set(&dev_priv->mksstat_kern_pids[i], 0);

				__free_pages(page, MKSSTAT_KERNEL_PAGES_ORDER);
				continue;
			}
		}

		ret = -EAGAIN;
	}

#endif
	return ret;
}

/**
 * vmw_mksstat_reset_ioctl: Resets all mksGuestStat instance descriptors
 * from the hypervisor.
 *
 * Discard all hypervisor PFN mappings, containing active mksGuestStat instance
 * descriptors, unpin the related userspace pages and free the related kernel pages.
 *
 * @dev: Identifies the drm device.
 * @data: Pointer to the ioctl argument.
 * @file_priv: Identifies the caller; unused.
 * Return: Zero on success, negative error code on error.
 */

int vmw_mksstat_reset_ioctl(struct drm_device *dev, void *data,
				struct drm_file *file_priv)
{
	struct vmw_private *const dev_priv = vmw_priv(dev);
	return vmw_mksstat_remove_all(dev_priv);
}

/**
 * vmw_mksstat_add_ioctl: Creates a single userspace-originating mksGuestStat
 * instance descriptor and registers that with the hypervisor.
 *
 * Create a hypervisor PFN mapping, containing a single mksGuestStat instance
 * descriptor and pin the corresponding userspace pages.
 *
 * @dev: Identifies the drm device.
 * @data: Pointer to the ioctl argument.
 * @file_priv: Identifies the caller; unused.
 * Return: Zero on success, negative error code on error.
 */

int vmw_mksstat_add_ioctl(struct drm_device *dev, void *data,
				struct drm_file *file_priv)
{
	struct drm_vmw_mksstat_add_arg *arg =
		(struct drm_vmw_mksstat_add_arg *) data;

	struct vmw_private *const dev_priv = vmw_priv(dev);

	struct page *page;
	MKSGuestStatInstanceDescriptor *pdesc;
	const size_t num_pages_stat = PFN_UP(arg->stat_len);
	const size_t num_pages_info = PFN_UP(arg->info_len);
	const size_t num_pages_strs = PFN_UP(arg->strs_len);
	long desc_len;
	long nr_pinned_stat;
	long nr_pinned_info;
	long nr_pinned_strs;
	struct page *pages_stat[ARRAY_SIZE(pdesc->statPPNs)];
	struct page *pages_info[ARRAY_SIZE(pdesc->infoPPNs)];
	struct page *pages_strs[ARRAY_SIZE(pdesc->strsPPNs)];
	size_t i, slot;

	arg->id = -1;

	if (!arg->stat || !arg->info || !arg->strs)
		return -EINVAL;

	if (!arg->stat_len || !arg->info_len || !arg->strs_len)
		return -EINVAL;

	if (!arg->description)
		return -EINVAL;

	if (num_pages_stat > ARRAY_SIZE(pdesc->statPPNs) ||
		num_pages_info > ARRAY_SIZE(pdesc->infoPPNs) ||
		num_pages_strs > ARRAY_SIZE(pdesc->strsPPNs))
		return -EINVAL;

	/* Find an available slot in the mksGuestStats user array and reserve it */
	for (slot = 0; slot < ARRAY_SIZE(dev_priv->mksstat_user_pids); ++slot)
		if (!atomic_cmpxchg(&dev_priv->mksstat_user_pids[slot], 0, MKSSTAT_PID_RESERVED))
			break;

	if (slot == ARRAY_SIZE(dev_priv->mksstat_user_pids))
		return -ENOSPC;

	BUG_ON(dev_priv->mksstat_user_pages[slot]);

	/* Allocate a page for the instance descriptor */
	page = alloc_page(GFP_KERNEL | __GFP_ZERO);

	if (!page) {
		atomic_set(&dev_priv->mksstat_user_pids[slot], 0);
		return -ENOMEM;
	}

	/* Set up the instance descriptor */
	pdesc = page_address(page);

	pdesc->reservedMBZ = 0;
	pdesc->statStartVA = arg->stat;
	pdesc->strsStartVA = arg->strs;
	pdesc->statLength = arg->stat_len;
	pdesc->infoLength = arg->info_len;
	pdesc->strsLength = arg->strs_len;
	desc_len = strncpy_from_user(pdesc->description, u64_to_user_ptr(arg->description),
		ARRAY_SIZE(pdesc->description) - 1);

	if (desc_len < 0) {
		atomic_set(&dev_priv->mksstat_user_pids[slot], 0);
		__free_page(page);
		return -EFAULT;
	}

	reset_ppn_array(pdesc->statPPNs, ARRAY_SIZE(pdesc->statPPNs));
	reset_ppn_array(pdesc->infoPPNs, ARRAY_SIZE(pdesc->infoPPNs));
	reset_ppn_array(pdesc->strsPPNs, ARRAY_SIZE(pdesc->strsPPNs));

	/* Pin mksGuestStat user pages and store those in the instance descriptor */
	nr_pinned_stat = pin_user_pages_fast(arg->stat, num_pages_stat, FOLL_LONGTERM, pages_stat);
	if (num_pages_stat != nr_pinned_stat)
		goto err_pin_stat;

	for (i = 0; i < num_pages_stat; ++i)
		pdesc->statPPNs[i] = page_to_pfn(pages_stat[i]);

	nr_pinned_info = pin_user_pages_fast(arg->info, num_pages_info, FOLL_LONGTERM, pages_info);
	if (num_pages_info != nr_pinned_info)
		goto err_pin_info;

	for (i = 0; i < num_pages_info; ++i)
		pdesc->infoPPNs[i] = page_to_pfn(pages_info[i]);

	nr_pinned_strs = pin_user_pages_fast(arg->strs, num_pages_strs, FOLL_LONGTERM, pages_strs);
	if (num_pages_strs != nr_pinned_strs)
		goto err_pin_strs;

	for (i = 0; i < num_pages_strs; ++i)
		pdesc->strsPPNs[i] = page_to_pfn(pages_strs[i]);

	/* Send the descriptor to the host via a hypervisor call. The mksGuestStat
	   pages will remain in use until the user requests a matching remove stats
	   or a stats reset occurs. */
	hypervisor_ppn_add((PPN64)page_to_pfn(page));

	dev_priv->mksstat_user_pages[slot] = page;
	atomic_set(&dev_priv->mksstat_user_pids[slot], task_pgrp_vnr(current));

	arg->id = slot;

	DRM_DEV_INFO(dev->dev, "pid=%d arg.description='%.*s' id=%zu\n", current->pid, (int)desc_len, pdesc->description, slot);

	return 0;

err_pin_strs:
	if (nr_pinned_strs > 0)
		unpin_user_pages(pages_strs, nr_pinned_strs);

err_pin_info:
	if (nr_pinned_info > 0)
		unpin_user_pages(pages_info, nr_pinned_info);

err_pin_stat:
	if (nr_pinned_stat > 0)
		unpin_user_pages(pages_stat, nr_pinned_stat);

	atomic_set(&dev_priv->mksstat_user_pids[slot], 0);
	__free_page(page);
	return -ENOMEM;
}

/**
 * vmw_mksstat_remove_ioctl: Removes a single userspace-originating mksGuestStat
 * instance descriptor from the hypervisor.
 *
 * Discard a hypervisor PFN mapping, containing a single mksGuestStat instance
 * descriptor and unpin the corresponding userspace pages.
 *
 * @dev: Identifies the drm device.
 * @data: Pointer to the ioctl argument.
 * @file_priv: Identifies the caller; unused.
 * Return: Zero on success, negative error code on error.
 */

int vmw_mksstat_remove_ioctl(struct drm_device *dev, void *data,
				struct drm_file *file_priv)
{
	struct drm_vmw_mksstat_remove_arg *arg =
		(struct drm_vmw_mksstat_remove_arg *) data;

	struct vmw_private *const dev_priv = vmw_priv(dev);

	const size_t slot = arg->id;
	pid_t pgid, pid;

	if (slot >= ARRAY_SIZE(dev_priv->mksstat_user_pids))
		return -EINVAL;

	DRM_DEV_INFO(dev->dev, "pid=%d arg.id=%zu\n", current->pid, slot);

	pgid = task_pgrp_vnr(current);
	pid = atomic_cmpxchg(&dev_priv->mksstat_user_pids[slot], pgid, MKSSTAT_PID_RESERVED);

	if (!pid)
		return 0;

	if (pid == pgid) {
		struct page *const page = dev_priv->mksstat_user_pages[slot];

		BUG_ON(!page);

		dev_priv->mksstat_user_pages[slot] = NULL;
		atomic_set(&dev_priv->mksstat_user_pids[slot], 0);

		hypervisor_ppn_remove((PPN64)page_to_pfn(page));

		vmw_mksstat_cleanup_descriptor(page);
		return 0;
	}

	return -EAGAIN;
}