drm/amdkfd: Simplify events page allocator

The first event page is always big enough to handle all events.
Handling of multiple events pages is not supported by user mode, and
not necessary.

Signed-off-by: Yong Zhao <[e-mail]>
Signed-off-by: Felix Kuehling <[e-mail]>
Acked-by: Oded Gabbay <[e-mail]>
Signed-off-by: Oded Gabbay <[e-mail]>

drivers/gpu/drm/amd/amdkfd/kfd_events.c

···
 	bool activated;		 /* Becomes true when event is signaled */
 };
 
+#define SLOTS_PER_PAGE KFD_SIGNAL_EVENT_LIMIT
+#define SLOT_BITMAP_LONGS BITS_TO_LONGS(SLOTS_PER_PAGE)
+
 /*
  * Over-complicated pooled allocator for event notification slots.
  *
···
  * Individual signal events are then allocated a slot in a page.
  */
 
-struct signal_page {
-	struct list_head event_pages;	/* kfd_process.signal_event_pages */
+struct kfd_signal_page {
 	uint64_t *kernel_address;
 	uint64_t __user *user_address;
-	uint32_t page_index;		/* Index into the mmap aperture. */
 	unsigned int free_slots;
-	unsigned long used_slot_bitmap[0];
+	unsigned long used_slot_bitmap[SLOT_BITMAP_LONGS];
 };
-
-#define SLOTS_PER_PAGE KFD_SIGNAL_EVENT_LIMIT
-#define SLOT_BITMAP_SIZE BITS_TO_LONGS(SLOTS_PER_PAGE)
-#define BITS_PER_PAGE (ilog2(SLOTS_PER_PAGE)+1)
-#define SIGNAL_PAGE_SIZE (sizeof(struct signal_page) + \
-				SLOT_BITMAP_SIZE * sizeof(long))
 
 /*
  * For signal events, the event ID is used as the interrupt user data.
···
  */
 
 #define INTERRUPT_DATA_BITS 8
-#define SIGNAL_EVENT_ID_SLOT_SHIFT 0
 
-static uint64_t *page_slots(struct signal_page *page)
+static uint64_t *page_slots(struct kfd_signal_page *page)
 {
 	return page->kernel_address;
 }
 
 static bool allocate_free_slot(struct kfd_process *process,
-				struct signal_page **out_page,
-				unsigned int *out_slot_index)
+			       unsigned int *out_slot_index)
 {
-	struct signal_page *page;
+	struct kfd_signal_page *page = process->signal_page;
+	unsigned int slot;
 
-	list_for_each_entry(page, &process->signal_event_pages, event_pages) {
-		if (page->free_slots > 0) {
-			unsigned int slot =
-				find_first_zero_bit(page->used_slot_bitmap,
-							SLOTS_PER_PAGE);
+	if (!page || page->free_slots == 0) {
+		pr_debug("No free event signal slots were found for process %p\n",
+			 process);
 
-			__set_bit(slot, page->used_slot_bitmap);
-			page->free_slots--;
-
-			page_slots(page)[slot] = UNSIGNALED_EVENT_SLOT;
-
-			*out_page = page;
-			*out_slot_index = slot;
-
-			pr_debug("Allocated event signal slot in page %p, slot %d\n",
-					page, slot);
-
-			return true;
-		}
+		return false;
 	}
 
-	pr_debug("No free event signal slots were found for process %p\n",
-			process);
+	slot = find_first_zero_bit(page->used_slot_bitmap, SLOTS_PER_PAGE);
 
-	return false;
+	__set_bit(slot, page->used_slot_bitmap);
+	page->free_slots--;
+
+	page_slots(page)[slot] = UNSIGNALED_EVENT_SLOT;
+
+	*out_slot_index = slot;
+
+	pr_debug("Allocated event signal slot in page %p, slot %d\n",
+		 page, slot);
+
+	return true;
 }
 
-#define list_tail_entry(head, type, member) \
-	list_entry((head)->prev, type, member)
-
-static bool allocate_signal_page(struct file *devkfd, struct kfd_process *p)
+static struct kfd_signal_page *allocate_signal_page(struct kfd_process *p)
 {
 	void *backing_store;
-	struct signal_page *page;
+	struct kfd_signal_page *page;
 
-	page = kzalloc(SIGNAL_PAGE_SIZE, GFP_KERNEL);
+	page = kzalloc(sizeof(*page), GFP_KERNEL);
 	if (!page)
-		goto fail_alloc_signal_page;
+		return NULL;
 
 	page->free_slots = SLOTS_PER_PAGE;
 
-	backing_store = (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
+	backing_store = (void *) __get_free_pages(GFP_KERNEL,
 					get_order(KFD_SIGNAL_EVENT_LIMIT * 8));
 	if (!backing_store)
 		goto fail_alloc_signal_store;
 
-	/* prevent user-mode info leaks */
+	/* Initialize all events to unsignaled */
 	memset(backing_store, (uint8_t) UNSIGNALED_EVENT_SLOT,
-		KFD_SIGNAL_EVENT_LIMIT * 8);
+	       KFD_SIGNAL_EVENT_LIMIT * 8);
 
 	page->kernel_address = backing_store;
-
-	if (list_empty(&p->signal_event_pages))
-		page->page_index = 0;
-	else
-		page->page_index = list_tail_entry(&p->signal_event_pages,
-						   struct signal_page,
-						   event_pages)->page_index + 1;
-
 	pr_debug("Allocated new event signal page at %p, for process %p\n",
 			page, p);
-	pr_debug("Page index is %d\n", page->page_index);
 
-	list_add(&page->event_pages, &p->signal_event_pages);
-
-	return true;
+	return page;
 
 fail_alloc_signal_store:
 	kfree(page);
-fail_alloc_signal_page:
-	return false;
+	return NULL;
 }
 
-static bool allocate_event_notification_slot(struct file *devkfd,
-					struct kfd_process *p,
-					struct signal_page **page,
-					unsigned int *signal_slot_index)
+static bool allocate_event_notification_slot(struct kfd_process *p,
+					     unsigned int *signal_slot_index)
 {
-	bool ret;
-
-	ret = allocate_free_slot(p, page, signal_slot_index);
-	if (!ret) {
-		ret = allocate_signal_page(devkfd, p);
-		if (ret)
-			ret = allocate_free_slot(p, page, signal_slot_index);
+	if (!p->signal_page) {
+		p->signal_page = allocate_signal_page(p);
+		if (!p->signal_page)
+			return false;
 	}
 
-	return ret;
+	return allocate_free_slot(p, signal_slot_index);
 }
 
 /* Assumes that the process's event_mutex is locked. */
-static void release_event_notification_slot(struct signal_page *page,
+static void release_event_notification_slot(struct kfd_signal_page *page,
 						size_t slot_index)
 {
 	__clear_bit(slot_index, page->used_slot_bitmap);
···
 	/* We don't free signal pages, they are retained by the process
 	 * and reused until it exits.
 	 */
-}
-
-static struct signal_page *lookup_signal_page_by_index(struct kfd_process *p,
-						unsigned int page_index)
-{
-	struct signal_page *page;
-
-	/*
-	 * This is safe because we don't delete signal pages until the
-	 * process exits.
-	 */
-	list_for_each_entry(page, &p->signal_event_pages, event_pages)
-		if (page->page_index == page_index)
-			return page;
-
-	return NULL;
 }
 
 /*
···
 			return ev;
 
 	return NULL;
-}
-
-static u32 make_signal_event_id(struct signal_page *page,
-					 unsigned int signal_slot_index)
-{
-	return page->page_index |
-			(signal_slot_index << SIGNAL_EVENT_ID_SLOT_SHIFT);
 }
 
 /*
···
 }
 
 static struct kfd_event *lookup_event_by_page_slot(struct kfd_process *p,
-						struct signal_page *page,
 						unsigned int signal_slot)
 {
-	return lookup_event_by_id(p, make_signal_event_id(page, signal_slot));
+	return lookup_event_by_id(p, signal_slot);
 }
 
 static int create_signal_event(struct file *devkfd,
···
 		return -ENOMEM;
 	}
 
-	if (!allocate_event_notification_slot(devkfd, p, &ev->signal_page,
-						&ev->signal_slot_index)) {
+	if (!allocate_event_notification_slot(p, &ev->signal_slot_index)) {
 		pr_warn("Signal event wasn't created because out of kernel memory\n");
 		return -ENOMEM;
 	}
···
 	p->signal_event_count++;
 
 	ev->user_signal_address =
-			&ev->signal_page->user_address[ev->signal_slot_index];
+			&p->signal_page->user_address[ev->signal_slot_index];
 
-	ev->event_id = make_signal_event_id(ev->signal_page,
-						ev->signal_slot_index);
+	ev->event_id = ev->signal_slot_index;
 
 	pr_debug("Signal event number %zu created with id %d, address %p\n",
 			p->signal_event_count, ev->event_id,
···
 {
 	mutex_init(&p->event_mutex);
 	hash_init(p->events);
-	INIT_LIST_HEAD(&p->signal_event_pages);
+	p->signal_page = NULL;
 	p->next_nonsignal_event_id = KFD_FIRST_NONSIGNAL_EVENT_ID;
 	p->signal_event_count = 0;
 }
···
 		waiter->event = NULL;
 	wake_up_all(&ev->wq);
 
-	if (ev->signal_page) {
-		release_event_notification_slot(ev->signal_page,
+	if ((ev->type == KFD_EVENT_TYPE_SIGNAL ||
+	     ev->type == KFD_EVENT_TYPE_DEBUG) && p->signal_page) {
+		release_event_notification_slot(p->signal_page,
 						ev->signal_slot_index);
 		p->signal_event_count--;
 	}
···
  * We assume that the process is being destroyed and there is no need to
  * unmap the pages or keep bookkeeping data in order.
  */
-static void shutdown_signal_pages(struct kfd_process *p)
+static void shutdown_signal_page(struct kfd_process *p)
 {
-	struct signal_page *page, *tmp;
+	struct kfd_signal_page *page = p->signal_page;
 
-	list_for_each_entry_safe(page, tmp, &p->signal_event_pages,
-					event_pages) {
+	if (page) {
 		free_pages((unsigned long)page->kernel_address,
 				get_order(KFD_SIGNAL_EVENT_LIMIT * 8));
 		kfree(page);
···
 void kfd_event_free_process(struct kfd_process *p)
 {
 	destroy_events(p);
-	shutdown_signal_pages(p);
+	shutdown_signal_page(p);
 }
 
 static bool event_can_be_gpu_signaled(const struct kfd_event *ev)
···
 	case KFD_EVENT_TYPE_DEBUG:
 		ret = create_signal_event(devkfd, p, ev);
 		if (!ret) {
-			*event_page_offset = (ev->signal_page->page_index |
-					KFD_MMAP_EVENTS_MASK);
+			*event_page_offset = KFD_MMAP_EVENTS_MASK;
 			*event_page_offset <<= PAGE_SHIFT;
 			*event_slot_index = ev->signal_slot_index;
 		}
···
 
 static void acknowledge_signal(struct kfd_process *p, struct kfd_event *ev)
 {
-	page_slots(ev->signal_page)[ev->signal_slot_index] =
+	page_slots(p->signal_page)[ev->signal_slot_index] =
 						UNSIGNALED_EVENT_SLOT;
 }
 
-static bool is_slot_signaled(struct signal_page *page, unsigned int index)
+static bool is_slot_signaled(struct kfd_process *p, unsigned int index)
 {
-	return page_slots(page)[index] != UNSIGNALED_EVENT_SLOT;
+	if (!p->signal_page)
+		return false;
+	else
+		return page_slots(p->signal_page)[index] !=
+			UNSIGNALED_EVENT_SLOT;
 }
 
 static void set_event_from_interrupt(struct kfd_process *p,
···
 		/* Partial ID is a full ID. */
 		ev = lookup_event_by_id(p, partial_id);
 		set_event_from_interrupt(p, ev);
-	} else {
+	} else if (p->signal_page) {
 		/*
 		 * Partial ID is in fact partial. For now we completely
 		 * ignore it, but we could use any bits we did receive to
 		 * search faster.
 		 */
-		struct signal_page *page;
 		unsigned int i;
 
-		list_for_each_entry(page, &p->signal_event_pages, event_pages)
-			for (i = 0; i < SLOTS_PER_PAGE; i++)
-				if (is_slot_signaled(page, i)) {
-					ev = lookup_event_by_page_slot(p,
-								page, i);
-					set_event_from_interrupt(p, ev);
-				}
+		for (i = 0; i < SLOTS_PER_PAGE; i++)
+			if (is_slot_signaled(p, i)) {
+				ev = lookup_event_by_page_slot(p, i);
+				set_event_from_interrupt(p, ev);
+			}
 	}
 
 	mutex_unlock(&p->event_mutex);
···
 int kfd_event_mmap(struct kfd_process *p, struct vm_area_struct *vma)
 {
 
-	unsigned int page_index;
 	unsigned long pfn;
-	struct signal_page *page;
+	struct kfd_signal_page *page;
 
 	/* check required size is logical */
 	if (get_order(KFD_SIGNAL_EVENT_LIMIT * 8) !=
···
 		return -EINVAL;
 	}
 
-	page_index = vma->vm_pgoff;
-
-	page = lookup_signal_page_by_index(p, page_index);
+	page = p->signal_page;
 	if (!page) {
 		/* Probably KFD bug, but mmap is user-accessible. */
-		pr_debug("Signal page could not be found for page_index %u\n",
-				page_index);
+		pr_debug("Signal page could not be found\n");
 		return -EINVAL;
 	}
 

drivers/gpu/drm/amd/amdkfd/kfd_events.h

···
 	wait_queue_head_t wq; /* List of event waiters. */
 
 	/* Only for signal events. */
-	struct signal_page *signal_page;
 	unsigned int signal_slot_index;
 	uint64_t __user *user_signal_address;
 

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

···
 	struct mutex event_mutex;
 	/* All events in process hashed by ID, linked on kfd_event.events. */
 	DECLARE_HASHTABLE(events, 4);
-	/* struct slot_page_header.event_pages */
-	struct list_head signal_event_pages;
+	/* Event page */
+	struct kfd_signal_page *signal_page;
 	u32 next_nonsignal_event_id;
 	size_t signal_event_count;
 	bool signal_event_limit_reached;