drm/amdkfd: Make event limit dependent on user mode mapping size

This allows increasing the KFD_SIGNAL_EVENT_LIMIT in kfd_ioctl.h
without breaking processes built with older kfd_ioctl.h versions.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

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

@@ -97,9 +97,17 @@ static int allocate_event_notification_slot(struct kfd_process *p,
 		p->signal_page = allocate_signal_page(p);
 		if (!p->signal_page)
 			return -ENOMEM;
+		/* Oldest user mode expects 256 event slots */
+		p->signal_mapped_size = 256*8;
 	}
 
-	id = idr_alloc(&p->event_idr, ev, 0, KFD_SIGNAL_EVENT_LIMIT,
+	/*
+	 * Compatibility with old user mode: Only use signal slots
+	 * user mode has mapped, may be less than
+	 * KFD_SIGNAL_EVENT_LIMIT. This also allows future increase
+	 * of the event limit without breaking user mode.
+	 */
+	id = idr_alloc(&p->event_idr, ev, 0, p->signal_mapped_size / 8,
 		       GFP_KERNEL);
 	if (id < 0)
 		return id;
@@ -173,7 +181,8 @@ static int create_signal_event(struct file *devkfd,
 {
 	int ret;
 
-	if (p->signal_event_count == KFD_SIGNAL_EVENT_LIMIT) {
+	if (p->signal_mapped_size &&
+	    p->signal_event_count == p->signal_mapped_size / 8) {
 		if (!p->signal_event_limit_reached) {
 			pr_warn("Signal event wasn't created because limit was reached\n");
 			p->signal_event_limit_reached = true;
@@ -744,12 +753,12 @@ int kfd_wait_on_events(struct kfd_process *p,
 
 int kfd_event_mmap(struct kfd_process *p, struct vm_area_struct *vma)
 {
-
 	unsigned long pfn;
 	struct kfd_signal_page *page;
+	int ret;
 
-	/* check required size is logical */
-	if (get_order(KFD_SIGNAL_EVENT_LIMIT * 8) !=
+	/* check required size doesn't exceed the allocated size */
+	if (get_order(KFD_SIGNAL_EVENT_LIMIT * 8) <
 			get_order(vma->vm_end - vma->vm_start)) {
 		pr_err("Event page mmap requested illegal size\n");
 		return -EINVAL;
@@ -779,8 +788,12 @@ int kfd_event_mmap(struct kfd_process *p, struct vm_area_struct *vma)
 	page->user_address = (uint64_t __user *)vma->vm_start;
 
 	/* mapping the page to user process */
-	return remap_pfn_range(vma, vma->vm_start, pfn,
+	ret = remap_pfn_range(vma, vma->vm_start, pfn,
 			vma->vm_end - vma->vm_start, vma->vm_page_prot);
+	if (!ret)
+		p->signal_mapped_size = vma->vm_end - vma->vm_start;
+
+	return ret;
 }
 
 /*

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

@@ -543,6 +543,7 @@ struct kfd_process {
 	struct idr event_idr;
 	/* Event page */
 	struct kfd_signal_page *signal_page;
+	size_t signal_mapped_size;
 	size_t signal_event_count;
 	bool signal_event_limit_reached;
 };