drm/vmwgfx: Introduce VMware mks-guest-stats

VMware mks-guest-stats mechanism allows the collection of performance stats from
guest userland GL contexts, as well as from vmwgfx kernelspace, via a set of sw-
defined performance counters. The userspace performance counters are (de)registerd
with vmware-vmx-stats hypervisor via new iocts. The vmwgfx kernelspace counters
are controlled at build-time via a new config DRM_VMWGFX_MKSSTATS.

* Add vmw_mksstat_{add|remove|reset}_ioctl controlling the tracking of
  mks-guest-stats in guest winsys contexts
* Add DRM_VMWGFX_MKSSTATS config to drivers/gpu/drm/vmwgfx/Kconfig controlling
  the instrumentation of vmwgfx for kernelspace mks-guest-stats counters
* Instrument vmwgfx vmw_execbuf_ioctl to collect mks-guest-stats according to
  DRM_VMWGFX_MKSSTATS

Signed-off-by: Martin Krastev <krastevm@vmware.com>
Reviewed-by: Zack Rusin <zackr@vmware.com>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210609172307.131929-3-zackr@vmware.com

8 files changed, 878 insertions, 27 deletions

diff --git a/drivers/gpu/drm/vmwgfx/Kconfig b/drivers/gpu/drm/vmwgfx/Kconfig
index 0060ef842b5a..a9052fae0bbc 100644
--- a/drivers/gpu/drm/vmwgfx/Kconfig
+++ b/drivers/gpu/drm/vmwgfx/Kconfig
@@ -22,3 +22,10 @@ config DRM_VMWGFX_FBCON
 	   Choose this option if you are shipping a new vmwgfx
 	   userspace driver that supports using the kernel driver.
 
+config DRM_VMWGFX_MKSSTATS
+	bool "Enable mksGuestStats instrumentation of vmwgfx by default"
+	depends on DRM_VMWGFX
+	default n
+	help
+	   Choose this option to instrument the kernel driver for mksGuestStats.
+
diff --git a/drivers/gpu/drm/vmwgfx/device_include/svga_types.h b/drivers/gpu/drm/vmwgfx/device_include/svga_types.h
index beddccee40f6..f5f79b114fac 100644
--- a/drivers/gpu/drm/vmwgfx/device_include/svga_types.h
+++ b/drivers/gpu/drm/vmwgfx/device_include/svga_types.h
@@ -23,9 +23,11 @@
  * SOFTWARE.
  *
  **********************************************************/
-#ifndef _VM_BASIC_TYPES_H_
-#define _VM_BASIC_TYPES_H_
+#ifndef _SVGA_TYPES_H_
+#define _SVGA_TYPES_H_
 #include <linux/kernel.h>
+#include <linux/mm.h>
+#include <asm/page.h>
 
 typedef u32 uint32;
 typedef s32 int32;
@@ -48,4 +50,90 @@ typedef bool Bool;
 
 #define CONST64U(x) x##ULL
 
+/*
+ * MKS Guest Stats types
+ */
+
+typedef struct MKSGuestStatCounter {
+	atomic64_t count;
+} MKSGuestStatCounter;
+
+typedef struct MKSGuestStatCounterTime {
+	MKSGuestStatCounter counter;
+	atomic64_t selfCycles;
+	atomic64_t totalCycles;
+} MKSGuestStatCounterTime;
+
+/*
+ * Flags for MKSGuestStatInfoEntry::flags below
+ */
+
+#define MKS_GUEST_STAT_FLAG_NONE    0
+#define MKS_GUEST_STAT_FLAG_TIME    (1U << 0)
+
+typedef __attribute__((aligned(32))) struct MKSGuestStatInfoEntry {
+	union {
+		const char *s;
+		uint64 u;
+	} name;
+	union {
+		const char *s;
+		uint64 u;
+	} description;
+	uint64 flags;
+	union {
+		MKSGuestStatCounter *counter;
+		MKSGuestStatCounterTime *counterTime;
+		uint64 u;
+	} stat;
+} MKSGuestStatInfoEntry;
+
+#define INVALID_PPN64       ((PPN64)0x000fffffffffffffULL)
+#define vmw_num_pages(size) (PAGE_ALIGN(size) >> PAGE_SHIFT)
+
+#define MKS_GUEST_STAT_INSTANCE_DESC_LENGTH 1024
+#define MKS_GUEST_STAT_INSTANCE_MAX_STATS   4096
+#define MKS_GUEST_STAT_INSTANCE_MAX_STAT_PPNS                \
+	(vmw_num_pages(MKS_GUEST_STAT_INSTANCE_MAX_STATS *   \
+		sizeof(MKSGuestStatCounterTime)))
+#define MKS_GUEST_STAT_INSTANCE_MAX_INFO_PPNS                \
+	(vmw_num_pages(MKS_GUEST_STAT_INSTANCE_MAX_STATS *   \
+		sizeof(MKSGuestStatInfoEntry)))
+#define MKS_GUEST_STAT_AVERAGE_NAME_LENGTH  40
+#define MKS_GUEST_STAT_INSTANCE_MAX_STRS_PPNS                \
+	(vmw_num_pages(MKS_GUEST_STAT_INSTANCE_MAX_STATS *   \
+		MKS_GUEST_STAT_AVERAGE_NAME_LENGTH))
+
+/*
+ * The MKSGuestStatInstanceDescriptor is used as main interface to
+ * communicate guest stats back to the host code.  The guest must
+ * allocate an instance of this structure at the start of a page and
+ * provide the physical address to the host.  From there the host code
+ * can walk this structure to find other (pinned) pages containing the
+ * stats data.
+ *
+ * Since the MKSGuestStatInfoEntry structures contain userlevel
+ * pointers, the InstanceDescriptor also contains pointers to the
+ * begining of these sections allowing the host side code to correctly
+ * interpret the pointers.
+ *
+ * Because the host side code never acknowledges anything back to the
+ * guest there is no strict requirement to maintain compatability
+ * across releases.  If the interface changes the host might not be
+ * able to log stats, but the guest will continue to run normally.
+ */
+
+typedef struct MKSGuestStatInstanceDescriptor {
+	uint64 reservedMBZ; /* must be zero for now. */
+	uint64 statStartVA; /* VA of the start of the stats section. */
+	uint64 strsStartVA; /* VA of the start of the strings section. */
+	uint64 statLength;  /* length of the stats section in bytes. */
+	uint64 infoLength;  /* length of the info entry section in bytes. */
+	uint64 strsLength;  /* length of the strings section in bytes. */
+	PPN64  statPPNs[MKS_GUEST_STAT_INSTANCE_MAX_STAT_PPNS]; /* stat counters */
+	PPN64  infoPPNs[MKS_GUEST_STAT_INSTANCE_MAX_INFO_PPNS]; /* stat info */
+	PPN64  strsPPNs[MKS_GUEST_STAT_INSTANCE_MAX_STRS_PPNS]; /* strings */
+	char   description[MKS_GUEST_STAT_INSTANCE_DESC_LENGTH];
+} MKSGuestStatInstanceDescriptor;
+
 #endif
diff --git a/drivers/gpu/drm/vmwgfx/device_include/vm_basic_types.h b/drivers/gpu/drm/vmwgfx/device_include/vm_basic_types.h
deleted file mode 100644
index 3a195e8106b3..000000000000
--- a/drivers/gpu/drm/vmwgfx/device_include/vm_basic_types.h
+++ /dev/null
@@ -1,22 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _VM_BASIC_TYPES_H_
-#define _VM_BASIC_TYPES_H_
-#include <linux/kernel.h>
-
-typedef u32 uint32;
-typedef s32 int32;
-typedef u64 uint64;
-typedef u16 uint16;
-typedef s16 int16;
-typedef u8  uint8;
-typedef s8  int8;
-
-typedef uint64 PA;
-typedef uint32 PPN;
-typedef uint64 PPN64;
-
-typedef bool Bool;
-
-#define MAX_UINT32 U32_MAX
-
-#endif
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 3e438de0f157..b9f18151663a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -43,6 +43,7 @@
 #include "vmwgfx_binding.h"
 #include "vmwgfx_devcaps.h"
 #include "vmwgfx_drv.h"
+#include "vmwgfx_mksstat.h"
 
 #define VMWGFX_DRIVER_DESC "Linux drm driver for VMware graphics devices"
 
@@ -148,6 +149,14 @@
 #define DRM_IOCTL_VMW_MSG						\
 	DRM_IOWR(DRM_COMMAND_BASE + DRM_VMW_MSG,			\
 		struct drm_vmw_msg_arg)
+#define DRM_IOCTL_VMW_MKSSTAT_RESET				\
+	DRM_IO(DRM_COMMAND_BASE + DRM_VMW_MKSSTAT_RESET)
+#define DRM_IOCTL_VMW_MKSSTAT_ADD				\
+	DRM_IOWR(DRM_COMMAND_BASE + DRM_VMW_MKSSTAT_ADD,	\
+		struct drm_vmw_mksstat_add_arg)
+#define DRM_IOCTL_VMW_MKSSTAT_REMOVE				\
+	DRM_IOW(DRM_COMMAND_BASE + DRM_VMW_MKSSTAT_REMOVE,	\
+		struct drm_vmw_mksstat_remove_arg)
 
 /*
  * The core DRM version of this macro doesn't account for
@@ -244,6 +253,15 @@ static const struct drm_ioctl_desc vmw_ioctls[] = {
 	VMW_IOCTL_DEF(VMW_MSG,
 		      vmw_msg_ioctl,
 		      DRM_RENDER_ALLOW),
+	VMW_IOCTL_DEF(VMW_MKSSTAT_RESET,
+		      vmw_mksstat_reset_ioctl,
+		      DRM_RENDER_ALLOW),
+	VMW_IOCTL_DEF(VMW_MKSSTAT_ADD,
+		      vmw_mksstat_add_ioctl,
+		      DRM_RENDER_ALLOW),
+	VMW_IOCTL_DEF(VMW_MKSSTAT_REMOVE,
+		      vmw_mksstat_remove_ioctl,
+		      DRM_RENDER_ALLOW),
 };
 
 static const struct pci_device_id vmw_pci_id_list[] = {
@@ -1137,6 +1155,8 @@ static void vmw_driver_unload(struct drm_device *dev)
 	for (i = vmw_res_context; i < vmw_res_max; ++i)
 		idr_destroy(&dev_priv->res_idr[i]);
 
+	vmw_mksstat_remove_all(dev_priv);
+
 	pci_release_regions(pdev);
 }
 
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
index 4c2afe9c0505..0d8699a43491 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
 /**************************************************************************
  *
- * Copyright 2009-2015 VMware, Inc., Palo Alto, CA., USA
+ * Copyright 2009-2021 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
@@ -91,6 +91,9 @@
 #define VMW_RES_FENCE ttm_driver_type3
 #define VMW_RES_SHADER ttm_driver_type4
 
+#define MKSSTAT_CAPACITY_LOG2 5U
+#define MKSSTAT_CAPACITY (1U << MKSSTAT_CAPACITY_LOG2)
+
 struct vmw_fpriv {
 	struct ttm_object_file *tfile;
 	bool gb_aware; /* user-space is guest-backed aware */
@@ -630,6 +633,18 @@ struct vmw_private {
 	struct vmw_validation_mem vvm;
 
 	uint32 *devcaps;
+
+	/*
+	 * mksGuestStat instance-descriptor and pid arrays
+	 */
+	struct page *mksstat_user_pages[MKSSTAT_CAPACITY];
+	atomic_t mksstat_user_pids[MKSSTAT_CAPACITY];
+
+#if IS_ENABLED(CONFIG_DRM_VMWGFX_MKSSTATS)
+	struct page *mksstat_kern_pages[MKSSTAT_CAPACITY];
+	u8 mksstat_kern_top_timer[MKSSTAT_CAPACITY];
+	atomic_t mksstat_kern_pids[MKSSTAT_CAPACITY];
+#endif
 };
 
 static inline struct vmw_surface *vmw_res_to_srf(struct vmw_resource *res)
@@ -1503,6 +1518,17 @@ __printf(1, 2) int vmw_host_printf(const char *fmt, ...);
 int vmw_msg_ioctl(struct drm_device *dev, void *data,
 		  struct drm_file *file_priv);
 
+/* Host mksGuestStats -vmwgfx_msg.c: */
+int vmw_mksstat_get_kern_slot(pid_t pid, struct vmw_private *dev_priv);
+
+int vmw_mksstat_reset_ioctl(struct drm_device *dev, void *data,
+		      struct drm_file *file_priv);
+int vmw_mksstat_add_ioctl(struct drm_device *dev, void *data,
+		      struct drm_file *file_priv);
+int vmw_mksstat_remove_ioctl(struct drm_device *dev, void *data,
+		      struct drm_file *file_priv);
+int vmw_mksstat_remove_all(struct vmw_private *dev_priv);
+
 /* VMW logging */
 
 /**
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index a2b8464b3f56..cd2621c8db38 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -32,6 +32,7 @@
 #include <drm/ttm/ttm_placement.h>
 #include "vmwgfx_so.h"
 #include "vmwgfx_binding.h"
+#include "vmwgfx_mksstat.h"
 
 #define VMW_RES_HT_ORDER 12
 
@@ -4406,6 +4407,9 @@ int vmw_execbuf_ioctl(struct drm_device *dev, void *data,
 	int ret;
 	struct dma_fence *in_fence = NULL;
 
+	MKS_STAT_TIME_DECL(MKSSTAT_KERN_EXECBUF);
+	MKS_STAT_TIME_PUSH(MKSSTAT_KERN_EXECBUF);
+
 	/*
 	 * Extend the ioctl argument while maintaining backwards compatibility:
 	 * We take different code paths depending on the value of arg->version.
@@ -4415,7 +4419,8 @@ int vmw_execbuf_ioctl(struct drm_device *dev, void *data,
 	if (unlikely(arg->version > DRM_VMW_EXECBUF_VERSION ||
 		     arg->version == 0)) {
 		VMW_DEBUG_USER("Incorrect execbuf version.\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto mksstats_out;
 	}
 
 	switch (arg->version) {
@@ -4435,7 +4440,8 @@ int vmw_execbuf_ioctl(struct drm_device *dev, void *data,
 
 		if (!in_fence) {
 			VMW_DEBUG_USER("Cannot get imported fence\n");
-			return -EINVAL;
+			ret = -EINVAL;
+			goto mksstats_out;
 		}
 
 		ret = vmw_wait_dma_fence(dev_priv->fman, in_fence);
@@ -4458,5 +4464,8 @@ int vmw_execbuf_ioctl(struct drm_device *dev, void *data,
 out:
 	if (in_fence)
 		dma_fence_put(in_fence);
+
+mksstats_out:
+	MKS_STAT_TIME_POP(MKSSTAT_KERN_EXECBUF);
 	return ret;
 }
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_mksstat.h b/drivers/gpu/drm/vmwgfx/vmwgfx_mksstat.h
new file mode 100644
index 000000000000..0509f55f07b4
--- /dev/null
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_mksstat.h
@@ -0,0 +1,144 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/**************************************************************************
+ *
+ * Copyright 2021 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.
+ *
+ **************************************************************************/
+
+#ifndef _VMWGFX_MKSSTAT_H_
+#define _VMWGFX_MKSSTAT_H_
+
+#include <asm/page.h>
+
+/* Reservation marker for mksstat pid's */
+#define MKSSTAT_PID_RESERVED -1
+
+#if IS_ENABLED(CONFIG_DRM_VMWGFX_MKSSTATS)
+/*
+ * Kernel-internal mksGuestStat counters. The order of this enum dictates the
+ * order of instantiation of these counters in the mksGuestStat pages.
+ */
+
+typedef enum {
+	MKSSTAT_KERN_EXECBUF, /* vmw_execbuf_ioctl */
+
+	MKSSTAT_KERN_COUNT /* Reserved entry; always last */
+} mksstat_kern_stats_t;
+
+/**
+ * vmw_mksstat_get_kern_pstat: Computes the address of the MKSGuestStatCounterTime
+ * array from the address of the base page.
+ *
+ * @page_addr: Pointer to the base page.
+ * Return: Pointer to the MKSGuestStatCounterTime array.
+ */
+
+static inline void *vmw_mksstat_get_kern_pstat(void *page_addr)
+{
+	return page_addr + PAGE_SIZE * 1;
+}
+
+/**
+ * vmw_mksstat_get_kern_pinfo: Computes the address of the MKSGuestStatInfoEntry
+ * array from the address of the base page.
+ *
+ * @page_addr: Pointer to the base page.
+ * Return: Pointer to the MKSGuestStatInfoEntry array.
+ */
+
+static inline void *vmw_mksstat_get_kern_pinfo(void *page_addr)
+{
+	return page_addr + PAGE_SIZE * 2;
+}
+
+/**
+ * vmw_mksstat_get_kern_pstrs: Computes the address of the mksGuestStat strings
+ * sequence from the address of the base page.
+ *
+ * @page_addr: Pointer to the base page.
+ * Return: Pointer to the mksGuestStat strings sequence.
+ */
+
+static inline void *vmw_mksstat_get_kern_pstrs(void *page_addr)
+{
+	return page_addr + PAGE_SIZE * 3;
+}
+
+/*
+ * MKS_STAT_TIME_DECL/PUSH/POP macros to be used in timer-counted routines.
+ */
+
+struct mksstat_timer_t {
+/* mutable */ mksstat_kern_stats_t old_top;
+	const u64 t0;
+	const int slot;
+};
+
+#define MKS_STAT_TIME_DECL(kern_cntr)                                     \
+	struct mksstat_timer_t _##kern_cntr = {                           \
+		.t0 = rdtsc(),                                            \
+		.slot = vmw_mksstat_get_kern_slot(current->pid, dev_priv) \
+	}
+
+#define MKS_STAT_TIME_PUSH(kern_cntr)                                                               \
+	do {                                                                                        \
+		if (_##kern_cntr.slot >= 0) {                                                       \
+			_##kern_cntr.old_top = dev_priv->mksstat_kern_top_timer[_##kern_cntr.slot]; \
+			dev_priv->mksstat_kern_top_timer[_##kern_cntr.slot] = kern_cntr;            \
+		}                                                                                   \
+	} while (0)
+
+#define MKS_STAT_TIME_POP(kern_cntr)                                                                                                           \
+	do {                                                                                                                                   \
+		if (_##kern_cntr.slot >= 0) {                                                                                                  \
+			const pid_t pid = atomic_cmpxchg(&dev_priv->mksstat_kern_pids[_##kern_cntr.slot], current->pid, MKSSTAT_PID_RESERVED); \
+			dev_priv->mksstat_kern_top_timer[_##kern_cntr.slot] = _##kern_cntr.old_top;                                            \
+			                                                                                                                       \
+			if (pid == current->pid) {                                                                                             \
+				const u64 dt = rdtsc() - _##kern_cntr.t0;                                                                      \
+				MKSGuestStatCounterTime *pstat;                                                                                \
+				                                                                                                               \
+				BUG_ON(!dev_priv->mksstat_kern_pages[_##kern_cntr.slot]);                                                      \
+				                                                                                                               \
+				pstat = vmw_mksstat_get_kern_pstat(page_address(dev_priv->mksstat_kern_pages[_##kern_cntr.slot]));             \
+				                                                                                                               \
+				atomic64_inc(&pstat[kern_cntr].counter.count);                                                                 \
+				atomic64_add(dt, &pstat[kern_cntr].selfCycles);                                                                \
+				atomic64_add(dt, &pstat[kern_cntr].totalCycles);                                                               \
+				                                                                                                               \
+				if (_##kern_cntr.old_top != MKSSTAT_KERN_COUNT)                                                                \
+					atomic64_sub(dt, &pstat[_##kern_cntr.old_top].selfCycles);                                             \
+					                                                                                                       \
+				atomic_set(&dev_priv->mksstat_kern_pids[_##kern_cntr.slot], current->pid);                                     \
+			}                                                                                                                      \
+		}                                                                                                                              \
+	} while (0)
+
+#else
+#define MKS_STAT_TIME_DECL(kern_cntr)
+#define MKS_STAT_TIME_PUSH(kern_cntr)
+#define MKS_STAT_TIME_POP(kern_cntr)
+
+#endif /* IS_ENABLED(CONFIG_DRM_VMWGFX_MKSSTATS */
+
+#endif
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
index 3d08f5700bdb..4218fe00e3b1 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
@@ -31,10 +31,12 @@
 #include <linux/mem_encrypt.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
@@ -56,6 +58,11 @@
 #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
@@ -612,3 +619,575 @@ out_open:
 
 	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,
+		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,
+		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 = vmw_num_pages(arg->stat_len);
+	const size_t num_pages_info = vmw_num_pages(arg->info_len);
+	const size_t num_pages_strs = vmw_num_pages(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);
+		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(arg->stat, num_pages_stat, FOLL_LONGTERM, pages_stat, NULL);
+	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(arg->info, num_pages_info, FOLL_LONGTERM, pages_info, NULL);
+	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(arg->strs, num_pages_strs, FOLL_LONGTERM, pages_strs, NULL);
+	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], current->pid);
+
+	arg->id = slot;
+
+	DRM_DEV_INFO(dev->dev, "pid=%d arg.description='%.*s' id=%lu\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 pid0;
+
+	if (slot >= ARRAY_SIZE(dev_priv->mksstat_user_pids))
+		return -EINVAL;
+
+	DRM_DEV_INFO(dev->dev, "pid=%d arg.id=%lu\n", current->pid, slot);
+
+	pid0 = atomic_read(&dev_priv->mksstat_user_pids[slot]);
+
+	if (!pid0)
+		return 0;
+
+	if (pid0 != MKSSTAT_PID_RESERVED) {
+		const pid_t pid1 = atomic_cmpxchg(&dev_priv->mksstat_user_pids[slot], pid0, MKSSTAT_PID_RESERVED);
+
+		if (!pid1)
+			return 0;
+
+		if (pid1 == pid0) {
+			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;
+}