[PATCH v5 4/8] drm/xe: Handle xe_user creation and removal

[Aakash Deep Sarkar <aakash.deep.sarkar@intel.com>]

We want our xe user structure to be created when a new
user id opens the xe device node and to be destroyed
when the final xe file with this uid is closed. In other
words the xe_user structure for a uid should remain in
scope as long as any process with this uid has an open
xe file descriptor.

To implement this we maintain an xarray of xe user
structures inside our xe device instance. Whenever a new
xe file is created via an open call, we check if the
calling process' uid is already present in our xarray.
If so, we increment the refcount for the associated
xe user and add this xe file to the list of xe files
belonging to this xe user. Otherwise, we allocate a
new xe user structure for this uid and initialize its
file list with this xe file.

Whenever an xe file is destroyed, we decrement the
refcount of the associated xe user. When the last
xe file in the xe user's file list is destroyed,
the xe user refcount should drop to zero and the
xe user should be cleaned up. During the cleanup path
we remove the xarray entry for this xe user in our
xe device and free up its memory.

Signed-off-by: Aakash Deep Sarkar <aakash.deep.sarkar@intel.com>
---
 drivers/gpu/drm/xe/xe_device.c       | 21 ++++++++
 drivers/gpu/drm/xe/xe_device_types.h | 16 ++++++
 drivers/gpu/drm/xe/xe_user.c         | 77 +++++++++++++++++++++++++++-
 drivers/gpu/drm/xe/xe_user.h         | 11 +++-
 4 files changed, 123 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 386940323630..5a084fd39876 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -65,6 +65,7 @@
 #include "xe_tile.h"
 #include "xe_ttm_stolen_mgr.h"
 #include "xe_ttm_sys_mgr.h"
+#include "xe_user.h"
 #include "xe_vm.h"
 #include "xe_vm_madvise.h"
 #include "xe_vram.h"
@@ -82,7 +83,9 @@ static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 	struct xe_drm_client *client;
 	struct xe_file *xef;
 	int ret = -ENOMEM;
+	int uid = -EINVAL;
 	struct task_struct *task = NULL;
+	const struct cred *cred = NULL;
 
 	xef = kzalloc(sizeof(*xef), GFP_KERNEL);
 	if (!xef)
@@ -107,8 +110,16 @@ static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 	file->driver_priv = xef;
 	kref_init(&xef->refcount);
 
+	INIT_LIST_HEAD(&xef->user_link);
+
 	task = get_pid_task(rcu_access_pointer(file->pid), PIDTYPE_PID);
 	if (task) {
+		cred = get_task_cred(task);
+		if (cred) {
+			uid = (unsigned int) cred->euid.val;
+			xe_user_init(xe, xef, uid);
+			put_cred(cred);
+		}
 		xef->process_name = kstrdup(task->comm, GFP_KERNEL);
 		xef->pid = task->pid;
 		put_task_struct(task);
@@ -128,6 +139,12 @@ static void xe_file_destroy(struct kref *ref)
 
 	xe_drm_client_put(xef->client);
 	kfree(xef->process_name);
+
+	mutex_lock(&xef->user->filelist_lock);
+	list_del(&xef->user_link);
+	mutex_unlock(&xef->user->filelist_lock);
+
+	xe_user_put(xef->user);
 	kfree(xef);
 }
 
@@ -467,6 +484,10 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 
 	xa_init_flags(&xe->usm.asid_to_vm, XA_FLAGS_ALLOC);
 
+	xa_init_flags(&xe->work_period.users, XA_FLAGS_ALLOC1);
+
+	mutex_init(&xe->work_period.lock);
+
 	if (IS_ENABLED(CONFIG_DRM_XE_DEBUG)) {
 		/* Trigger a large asid and an early asid wrap. */
 		u32 asid;
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index 54a612787289..4d4e9a63b3fd 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -613,6 +613,16 @@ struct xe_device {
 	atomic_t g2g_test_count;
 #endif
 
+	/**
+	 * @xe_work_period: Support for GPU work period tracepoint
+	 */
+	struct xe_work_period {
+		/** @users: list of users that have opened this xe device */
+		struct xarray users;
+		/** @lock: lock protecting this structure */
+		struct mutex lock;
+	} work_period;
+
 	/* private: */
 
 #if IS_ENABLED(CONFIG_DRM_XE_DISPLAY)
@@ -684,6 +694,12 @@ struct xe_file {
 	/** @active_duration_ns: total run time in ns for this xe file */
 	u64 active_duration_ns;
 
+	/** @user: pointer to struct xe_user associated with this xe file */
+	struct xe_user *user;
+
+	/** @user_link: link into xe_user::filelist */
+	struct list_head user_link;
+
 	/** @client: drm client */
 	struct xe_drm_client *client;
 
diff --git a/drivers/gpu/drm/xe/xe_user.c b/drivers/gpu/drm/xe/xe_user.c
index f35e18776300..cb3de75aa497 100644
--- a/drivers/gpu/drm/xe/xe_user.c
+++ b/drivers/gpu/drm/xe/xe_user.c
@@ -3,6 +3,8 @@
  * Copyright © 2025 Intel Corporation
  */
 
+#include <drm/drm_drv.h>
+
 #include "xe_user.h"
 
 
@@ -60,7 +62,7 @@
  *
  * Return: pointer to user struct or NULL if can't allocate
  */
-struct xe_user *xe_user_alloc(void)
+static struct xe_user *xe_user_alloc(void)
 {
 	struct xe_user *user;
 
@@ -71,6 +73,7 @@ struct xe_user *xe_user_alloc(void)
 	kref_init(&user->refcount);
 	mutex_init(&user->filelist_lock);
 	INIT_LIST_HEAD(&user->filelist);
+	INIT_WORK(&user->work, work_period_worker);
 	return user;
 }
 
@@ -84,6 +87,78 @@ void __xe_user_free(struct kref *kref)
 {
 	struct xe_user *user =
 		container_of(kref, struct xe_user, refcount);
+	struct xe_device *xe = user->xe;
+	void *lookup;
+
+	mutex_lock(&xe->work_period.lock);
+	lookup = xa_erase(&xe->work_period.users, user->id);
+	xe_assert(xe, lookup == user);
+	mutex_unlock(&xe->work_period.lock);
 
+	drm_dev_put(&user->xe->drm);
 	kfree(user);
 }
+
+static struct xe_user *xe_user_lookup(struct xe_device *xe, u32 uid)
+{
+	struct xe_user *user = NULL;
+	unsigned long i;
+
+	mutex_lock(&xe->work_period.lock);
+	xa_for_each(&xe->work_period.users, i, user) {
+		if (user->uid == uid) {
+			xe_user_get(user);
+			mutex_unlock(&xe->work_period.lock);
+			return user;
+		}
+	}
+	mutex_unlock(&xe->work_period.lock);
+
+	return NULL;
+}
+
+int xe_user_init(struct xe_device *xe, struct xe_file *xef, unsigned int uid)
+{
+	struct xe_user *user = NULL;
+	int ret;
+	u32 idx;
+	/*
+	 * Check if the calling process/uid has already been registered
+	 * with the xe device during a previous open call. If so then
+	 * take a reference to this xe user and add this xe file to the
+	 * filelist belonging to this xe user
+	 */
+	user = xe_user_lookup(xe, uid);
+	if (!user) {
+		/*
+		 * We couldn't find an existing xe user for the calling process.
+		 * Allocate a new struct xe_user and register it with this xe
+		 * device
+		 */
+		user = xe_user_alloc();
+		if (!user)
+			return -ENOMEM;
+
+
+		user->uid = uid;
+		user->last_timestamp_ns = ktime_get_raw_ns();
+		user->xe = xe;
+
+		mutex_lock(&xe->work_period.lock);
+		ret = xa_alloc(&xe->work_period.users, &idx, user, xa_limit_32b, GFP_KERNEL);
+		mutex_unlock(&xe->work_period.lock);
+
+		if (ret < 0)
+			return ret;
+
+		user->id = idx;
+		drm_dev_get(&xe->drm);
+	}
+
+	mutex_lock(&user->filelist_lock);
+	list_add(&xef->user_link, &user->filelist);
+	mutex_unlock(&user->filelist_lock);
+	xef->user = user;
+
+	return 0;
+}
diff --git a/drivers/gpu/drm/xe/xe_user.h b/drivers/gpu/drm/xe/xe_user.h
index 9628cc628a37..341200c55509 100644
--- a/drivers/gpu/drm/xe/xe_user.h
+++ b/drivers/gpu/drm/xe/xe_user.h
@@ -6,6 +6,9 @@
 #ifndef _XE_USER_H_
 #define _XE_USER_H_
 
+#include "xe_device.h"
+
+
 /**
  * struct xe_user - xe user structure
  *
@@ -40,6 +43,11 @@ struct xe_user {
 	 */
 	struct work_struct work;
 
+	/**
+	 * @id: index of this user into the xe device::users xarray
+	 */
+	u32 id;
+
 	/**
 	 * @uid: UID of this xe_user
 	 */
@@ -58,7 +66,8 @@ struct xe_user {
 	u64 last_timestamp_ns;
 };
 
-struct xe_user *xe_user_alloc(void);
+int xe_user_init(struct xe_device *xe, struct xe_file *xef, unsigned int uid);
+
 
 static inline struct xe_user *
 xe_user_get(struct xe_user *user)
-- 
2.49.0