drm/i915: Remove short-term pins from execbuf, v6.

Add a flag PIN_VALIDATE, to indicate we don't need to pin and only
protected by the object lock.

This removes the need to unpin, which is done by just releasing the
lock.

eb_reserve is slightly reworked for readability, but the same steps
are still done:
- First pass pins with NONBLOCK.
- Second pass unbinds all objects first, then pins.
- Third pass is only called when not all objects are softpinned, and
  unbinds all objects, then calls i915_gem_evict_vm(), then pins.

Changes since v1:
- Split out eb_reserve() into separate functions for readability.
Changes since v2:
- Make batch buffer mappable on platforms where only GGTT is available,
  to prevent moving the batch buffer during relocations.
Changes since v3:
- Preserve current behavior for batch buffer, instead be cautious when
  calling i915_gem_object_ggtt_pin_ww, and re-use the current batch vma
  if it's inside ggtt and map-and-fenceable.
- Remove impossible condition check from eb_reserve. (Matt)
Changes since v5:
- Do not even temporarily pin, just call i915_gem_evict_vm() and mark
  all vma's as unpinned.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220114132320.109030-7-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c

@@ -425,7 +425,6 @@ int i915_vma_pin_fence(struct i915_vma *vma)
 	 * must keep the device awake whilst using the fence.
 	 */
 	assert_rpm_wakelock_held(vma->vm->gt->uncore->rpm);
-	GEM_BUG_ON(!i915_vma_is_pinned(vma));
 	GEM_BUG_ON(!i915_vma_is_ggtt(vma));
 
 	err = mutex_lock_interruptible(&vma->vm->mutex);

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -44,6 +44,7 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,
 #define PIN_HIGH		BIT_ULL(5)
 #define PIN_OFFSET_BIAS		BIT_ULL(6)
 #define PIN_OFFSET_FIXED	BIT_ULL(7)
+#define PIN_VALIDATE		BIT_ULL(8) /* validate placement only, no need to call unpin() */
 
 #define PIN_GLOBAL		BIT_ULL(10) /* I915_VMA_GLOBAL_BIND */
 #define PIN_USER		BIT_ULL(11) /* I915_VMA_LOCAL_BIND */

drivers/gpu/drm/i915/i915_vma.c

@@ -840,6 +840,15 @@ static bool try_qad_pin(struct i915_vma *vma, unsigned int flags)
 	unsigned int bound;
 
 	bound = atomic_read(&vma->flags);
+
+	if (flags & PIN_VALIDATE) {
+		flags &= I915_VMA_BIND_MASK;
+
+		return (flags & bound) == flags;
+	}
+
+	/* with the lock mandatory for unbind, we don't race here */
+	flags &= I915_VMA_BIND_MASK;
 	do {
 		if (unlikely(flags & ~bound))
 			return false;
@@ -1261,7 +1270,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 	GEM_BUG_ON(!(flags & (PIN_USER | PIN_GLOBAL)));
 
 	/* First try and grab the pin without rebinding the vma */
-	if (try_qad_pin(vma, flags & I915_VMA_BIND_MASK))
+	if (try_qad_pin(vma, flags))
 		return 0;
 
 	err = i915_vma_get_pages(vma);
@@ -1349,7 +1358,8 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 	}
 
 	if (unlikely(!(flags & ~bound & I915_VMA_BIND_MASK))) {
-		__i915_vma_pin(vma);
+		if (!(flags & PIN_VALIDATE))
+			__i915_vma_pin(vma);
 		goto err_unlock;
 	}
 
@@ -1379,8 +1389,10 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 	atomic_add(I915_VMA_PAGES_ACTIVE, &vma->pages_count);
 	list_move_tail(&vma->vm_link, &vma->vm->bound_list);
 
-	__i915_vma_pin(vma);
-	GEM_BUG_ON(!i915_vma_is_pinned(vma));
+	if (!(flags & PIN_VALIDATE)) {
+		__i915_vma_pin(vma);
+		GEM_BUG_ON(!i915_vma_is_pinned(vma));
+	}
 	GEM_BUG_ON(!i915_vma_is_bound(vma, flags));
 	GEM_BUG_ON(i915_vma_misplaced(vma, size, alignment, flags));
 
@@ -1643,8 +1655,6 @@ static int __i915_vma_move_to_active(struct i915_vma *vma, struct i915_request *
 {
 	int err;
 
-	GEM_BUG_ON(!i915_vma_is_pinned(vma));
-
 	/* Wait for the vma to be bound before we start! */
 	err = __i915_request_await_bind(rq, vma);
 	if (err)
@@ -1663,6 +1673,8 @@ int _i915_vma_move_to_active(struct i915_vma *vma,
 
 	assert_object_held(obj);
 
+	GEM_BUG_ON(!vma->pages);
+
 	err = __i915_vma_move_to_active(vma, rq);
 	if (unlikely(err))
 		return err;