[RFC 03/19] drm/xe/eudebug: Introduce discovery for resources

[Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>]

From: Mika Kuoppala <mika.kuoppala@linux.intel.com>

Debugger connection can happen way after the client has
created and destroyed arbitrary number of resources.

We need to playback all currently existing resources for the
debugger. The client is held until this so called discovery
process, executed by workqueue, is complete.

This patch is based on discovery work by Maciej Patelczyk
for i915 driver.

v2: - use rw_semaphore to block drm_ioctls during discovery (Matthew)
    - only lock according to ioctl at play (Dominik)

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Dominik Grzegorzek <dominik.grzegorzek@intel.com>
Co-developed-by: Maciej Patelczyk <maciej.patelczyk@intel.com>
Signed-off-by: Maciej Patelczyk <maciej.patelczyk@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Acked-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
---
 drivers/gpu/drm/xe/xe_device.c        |  10 +-
 drivers/gpu/drm/xe/xe_device.h        |  34 +++++++
 drivers/gpu/drm/xe/xe_device_types.h  |   6 ++
 drivers/gpu/drm/xe/xe_eudebug.c       | 135 +++++++++++++++++++++++++-
 drivers/gpu/drm/xe/xe_eudebug_types.h |   7 ++
 5 files changed, 185 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 40d514003eee..17a1b6f37d1d 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -216,8 +216,11 @@ static long xe_drm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		return -ECANCELED;
 
 	ret = xe_pm_runtime_get_ioctl(xe);
-	if (ret >= 0)
+	if (ret >= 0) {
+		xe_eudebug_discovery_lock(xe, cmd);
 		ret = drm_ioctl(file, cmd, arg);
+		xe_eudebug_discovery_unlock(xe, cmd);
+	}
 	xe_pm_runtime_put(xe);
 
 	return ret;
@@ -234,8 +237,11 @@ static long xe_drm_compat_ioctl(struct file *file, unsigned int cmd, unsigned lo
 		return -ECANCELED;
 
 	ret = xe_pm_runtime_get_ioctl(xe);
-	if (ret >= 0)
+	if (ret >= 0) {
+		xe_eudebug_discovery_lock(xe, cmd);
 		ret = drm_compat_ioctl(file, cmd, arg);
+		xe_eudebug_discovery_unlock(xe, cmd);
+	}
 	xe_pm_runtime_put(xe);
 
 	return ret;
diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
index 4c3f0ebe78a9..b2fc85b1d26e 100644
--- a/drivers/gpu/drm/xe/xe_device.h
+++ b/drivers/gpu/drm/xe/xe_device.h
@@ -7,6 +7,7 @@
 #define _XE_DEVICE_H_
 
 #include <drm/drm_util.h>
+#include <drm/drm_ioctl.h>
 
 #include "xe_device_types.h"
 #include "xe_gt_types.h"
@@ -191,4 +192,37 @@ void xe_device_declare_wedged(struct xe_device *xe);
 struct xe_file *xe_file_get(struct xe_file *xef);
 void xe_file_put(struct xe_file *xef);
 
+#if IS_ENABLED(CONFIG_DRM_XE_EUDEBUG)
+static inline int xe_eudebug_needs_lock(const unsigned int cmd)
+{
+	const unsigned int xe_cmd = DRM_IOCTL_NR(cmd) - DRM_COMMAND_BASE;
+
+	switch (xe_cmd) {
+	case DRM_XE_VM_CREATE:
+	case DRM_XE_VM_DESTROY:
+	case DRM_XE_VM_BIND:
+	case DRM_XE_EXEC_QUEUE_CREATE:
+	case DRM_XE_EXEC_QUEUE_DESTROY:
+	case DRM_XE_EUDEBUG_CONNECT:
+		return 1;
+	}
+
+	return 0;
+}
+
+static inline void xe_eudebug_discovery_lock(struct xe_device *xe, unsigned int cmd)
+{
+	if (xe_eudebug_needs_lock(cmd))
+		down_read(&xe->eudebug.discovery_lock);
+}
+static inline void xe_eudebug_discovery_unlock(struct xe_device *xe, unsigned int cmd)
+{
+	if (xe_eudebug_needs_lock(cmd))
+		up_read(&xe->eudebug.discovery_lock);
+}
+#else
+static inline void xe_eudebug_discovery_lock(struct xe_device *xe, unsigned int cmd) { }
+static inline void xe_eudebug_discovery_unlock(struct xe_device *xe, unsigned int cmd) { }
+#endif /* CONFIG_DRM_XE_EUDEBUG */
+
 #endif
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index cb4b52888a4b..54ceeee7cf75 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -542,6 +542,12 @@ struct xe_device {
 
 		/** @available: is the debugging functionality available */
 		bool available;
+
+		/** @ordered_wq: used to discovery */
+		struct workqueue_struct *ordered_wq;
+
+		/** discovery_lock: used for discovery to block xe ioctls */
+		struct rw_semaphore discovery_lock;
 	} eudebug;
 #endif
 
diff --git a/drivers/gpu/drm/xe/xe_eudebug.c b/drivers/gpu/drm/xe/xe_eudebug.c
index da62f699f514..c79dab6d61a7 100644
--- a/drivers/gpu/drm/xe/xe_eudebug.c
+++ b/drivers/gpu/drm/xe/xe_eudebug.c
@@ -299,6 +299,8 @@ static bool xe_eudebug_detach(struct xe_device *xe,
 	}
 	spin_unlock(&d->connection.lock);
 
+	flush_work(&d->discovery_work);
+
 	if (!detached)
 		return false;
 
@@ -409,7 +411,7 @@ static struct task_struct *find_task_get(struct xe_file *xef)
 }
 
 static struct xe_eudebug *
-xe_eudebug_get(struct xe_file *xef)
+_xe_eudebug_get(struct xe_file *xef)
 {
 	struct task_struct *task;
 	struct xe_eudebug *d;
@@ -433,6 +435,24 @@ xe_eudebug_get(struct xe_file *xef)
 	return d;
 }
 
+static struct xe_eudebug *
+xe_eudebug_get(struct xe_file *xef)
+{
+	struct xe_eudebug *d;
+
+	lockdep_assert_held(&xef->xe->eudebug.discovery_lock);
+
+	d = _xe_eudebug_get(xef);
+	if (d) {
+		if (!completion_done(&d->discovery)) {
+			xe_eudebug_put(d);
+			d = NULL;
+		}
+	}
+
+	return d;
+}
+
 static int xe_eudebug_queue_event(struct xe_eudebug *d,
 				  struct xe_eudebug_event *event)
 {
@@ -810,6 +830,10 @@ static long xe_eudebug_ioctl(struct file *file,
 	struct xe_eudebug * const d = file->private_data;
 	long ret;
 
+	if (cmd != DRM_XE_EUDEBUG_IOCTL_READ_EVENT &&
+	    !completion_done(&d->discovery))
+		return -EBUSY;
+
 	switch (cmd) {
 	case DRM_XE_EUDEBUG_IOCTL_READ_EVENT:
 		ret = xe_eudebug_read_event(d, arg,
@@ -831,6 +855,8 @@ static const struct file_operations fops = {
 	.unlocked_ioctl	= xe_eudebug_ioctl,
 };
 
+static void discovery_work_fn(struct work_struct *work);
+
 static int
 xe_eudebug_connect(struct xe_device *xe,
 		   struct drm_xe_eudebug_connect *param)
@@ -865,9 +891,11 @@ xe_eudebug_connect(struct xe_device *xe,
 	spin_lock_init(&d->connection.lock);
 	init_waitqueue_head(&d->events.write_done);
 	init_waitqueue_head(&d->events.read_done);
+	init_completion(&d->discovery);
 
 	spin_lock_init(&d->events.lock);
 	INIT_KFIFO(d->events.fifo);
+	INIT_WORK(&d->discovery_work, discovery_work_fn);
 
 	d->res = xe_eudebug_resources_alloc();
 	if (IS_ERR(d->res)) {
@@ -885,6 +913,9 @@ xe_eudebug_connect(struct xe_device *xe,
 		goto err_detach;
 	}
 
+	kref_get(&d->ref);
+	queue_work(xe->eudebug.ordered_wq, &d->discovery_work);
+
 	eu_dbg(d, "connected session %lld", d->session);
 
 	return fd;
@@ -917,13 +948,18 @@ void xe_eudebug_init(struct xe_device *xe)
 	spin_lock_init(&xe->eudebug.lock);
 	INIT_LIST_HEAD(&xe->eudebug.list);
 	INIT_LIST_HEAD(&xe->clients.list);
+	init_rwsem(&xe->eudebug.discovery_lock);
 
-	xe->eudebug.available = true;
+	xe->eudebug.ordered_wq = alloc_ordered_workqueue("xe-eudebug-ordered-wq", 0);
+	xe->eudebug.available = !!xe->eudebug.ordered_wq;
 }
 
 void xe_eudebug_fini(struct xe_device *xe)
 {
 	xe_assert(xe, list_empty_careful(&xe->eudebug.list));
+
+	if (xe->eudebug.ordered_wq)
+		destroy_workqueue(xe->eudebug.ordered_wq);
 }
 
 static int send_open_event(struct xe_eudebug *d, u32 flags, const u64 handle,
@@ -989,21 +1025,25 @@ void xe_eudebug_file_open(struct xe_file *xef)
 	struct xe_eudebug *d;
 
 	INIT_LIST_HEAD(&xef->eudebug.client_link);
+
+	down_read(&xef->xe->eudebug.discovery_lock);
+
 	spin_lock(&xef->xe->clients.lock);
 	list_add_tail(&xef->eudebug.client_link, &xef->xe->clients.list);
 	spin_unlock(&xef->xe->clients.lock);
 
 	d = xe_eudebug_get(xef);
-	if (!d)
-		return;
+	if (d)
+		xe_eudebug_event_put(d, client_create_event(d, xef));
 
-	xe_eudebug_event_put(d, client_create_event(d, xef));
+	up_read(&xef->xe->eudebug.discovery_lock);
 }
 
 void xe_eudebug_file_close(struct xe_file *xef)
 {
 	struct xe_eudebug *d;
 
+	down_read(&xef->xe->eudebug.discovery_lock);
 	d = xe_eudebug_get(xef);
 	if (d)
 		xe_eudebug_event_put(d, client_destroy_event(d, xef));
@@ -1011,6 +1051,8 @@ void xe_eudebug_file_close(struct xe_file *xef)
 	spin_lock(&xef->xe->clients.lock);
 	list_del_init(&xef->eudebug.client_link);
 	spin_unlock(&xef->xe->clients.lock);
+
+	up_read(&xef->xe->eudebug.discovery_lock);
 }
 
 static int send_vm_event(struct xe_eudebug *d, u32 flags,
@@ -1111,3 +1153,86 @@ void xe_eudebug_vm_destroy(struct xe_file *xef, struct xe_vm *vm)
 
 	xe_eudebug_event_put(d, vm_destroy_event(d, xef, vm));
 }
+
+static int discover_client(struct xe_eudebug *d, struct xe_file *xef)
+{
+	struct xe_vm *vm;
+	unsigned long i;
+	int err;
+
+	err = client_create_event(d, xef);
+	if (err)
+		return err;
+
+	xa_for_each(&xef->vm.xa, i, vm) {
+		err = vm_create_event(d, xef, vm);
+		if (err)
+			break;
+	}
+
+	return err;
+}
+
+static bool xe_eudebug_task_match(struct xe_eudebug *d, struct xe_file *xef)
+{
+	struct task_struct *task;
+	bool match;
+
+	task = find_task_get(xef);
+	if (!task)
+		return false;
+
+	match = same_thread_group(d->target_task, task);
+
+	put_task_struct(task);
+
+	return match;
+}
+
+static void discover_clients(struct xe_device *xe, struct xe_eudebug *d)
+{
+	struct xe_file *xef;
+	int err;
+
+	list_for_each_entry(xef, &xe->clients.list, eudebug.client_link) {
+		if (xe_eudebug_detached(d))
+			break;
+
+		if (xe_eudebug_task_match(d, xef))
+			err = discover_client(d, xef);
+		else
+			err = 0;
+
+		if (err) {
+			eu_dbg(d, "discover client %p: %d\n", xef, err);
+			break;
+		}
+	}
+}
+
+static void discovery_work_fn(struct work_struct *work)
+{
+	struct xe_eudebug *d = container_of(work, typeof(*d),
+					    discovery_work);
+	struct xe_device *xe = d->xe;
+
+	if (xe_eudebug_detached(d)) {
+		complete_all(&d->discovery);
+		xe_eudebug_put(d);
+		return;
+	}
+
+	down_write(&xe->eudebug.discovery_lock);
+
+	eu_dbg(d, "Discovery start for %lld\n", d->session);
+
+	discover_clients(xe, d);
+
+	eu_dbg(d, "Discovery end for %lld\n", d->session);
+
+	complete_all(&d->discovery);
+
+	up_write(&xe->eudebug.discovery_lock);
+
+	xe_eudebug_put(d);
+}
diff --git a/drivers/gpu/drm/xe/xe_eudebug_types.h b/drivers/gpu/drm/xe/xe_eudebug_types.h
index a5185f18f640..080a821db3e4 100644
--- a/drivers/gpu/drm/xe/xe_eudebug_types.h
+++ b/drivers/gpu/drm/xe/xe_eudebug_types.h
@@ -19,6 +19,7 @@
 struct xe_device;
 struct task_struct;
 struct xe_eudebug_event;
+struct workqueue_struct;
 
 #define CONFIG_DRM_XE_DEBUGGER_EVENT_QUEUE_SIZE 64
 
@@ -96,6 +97,12 @@ struct xe_eudebug {
 	/** @session: session number for this connection (for logs) */
 	u64 session;
 
+	/** @discovery: completion to wait for discovery */
+	struct completion discovery;
+
+	/** @discovery_work: worker to discover resources for target_task */
+	struct work_struct discovery_work;
+
 	/** @events: kfifo queue of to-be-delivered events */
 	struct {
 		/** @lock: guards access to fifo */
-- 
2.46.1