drm/i915: Add support for moving fence waiting

For now, we will only allow async migration when TTM is used,
so the paths we care about are related to TTM.

The mmap path is handled by having the fence in ttm_bo->moving,
when pinning, the binding only becomes available after the moving
fence is signaled, and pinning a cpu map will only work after
the moving fence signals.

This should close all holes where userspace can read a buffer
before it's fully migrated.

v2:
- Fix a couple of SPARSE warnings
v3:
- Fix a NULL pointer dereference
v4:
- Ditch the moving fence waiting for i915_vma_pin_iomap() and
  replace with a verification that the vma is already bound.
  (Matthew Auld)
- Squash with a previous patch introducing moving fence waiting and
  accessing interfaces (Matthew Auld)
- Rename to indicated that we also add support for sync waiting.
v5:
- Fix check for NULL and unreferencing i915_vma_verify_bind_complete()
  (Matthew Auld)
- Fix compilation failure if !CONFIG_DRM_I915_DEBUG_GEM
- Fix include ordering. (Matthew Auld)
v7:
- Fix yet another compilation failure with clang if
  !CONFIG_DRM_I915_DEBUG_GEM

Co-developed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
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/20211122214554.371864-2-thomas.hellstrom@linux.intel.com

1 files changed, 42 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index e2f2c4c52009..927f0d4f8e11 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -353,6 +353,32 @@ int i915_vma_wait_for_bind(struct i915_vma *vma)
 	return err;
 }
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
+static int i915_vma_verify_bind_complete(struct i915_vma *vma)
+{
+	int err = 0;
+
+	if (i915_active_has_exclusive(&vma->active)) {
+		struct dma_fence *fence =
+			i915_active_fence_get(&vma->active.excl);
+
+		if (!fence)
+			return 0;
+
+		if (dma_fence_is_signaled(fence))
+			err = fence->error;
+		else
+			err = -EBUSY;
+
+		dma_fence_put(fence);
+	}
+
+	return err;
+}
+#else
+#define i915_vma_verify_bind_complete(_vma) 0
+#endif
+
 /**
  * i915_vma_bind - Sets up PTEs for an VMA in it's corresponding address space.
  * @vma: VMA to map
@@ -425,6 +451,13 @@ int i915_vma_bind(struct i915_vma *vma,
 		__i915_gem_object_pin_pages(vma->obj);
 		work->pinned = i915_gem_object_get(vma->obj);
 	} else {
+		if (vma->obj) {
+			int ret;
+
+			ret = i915_gem_object_wait_moving_fence(vma->obj, true);
+			if (ret)
+				return ret;
+		}
 		vma->ops->bind_vma(vma->vm, NULL, vma, cache_level, bind_flags);
 	}
 
@@ -446,6 +479,7 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)
 
 	GEM_BUG_ON(!i915_vma_is_ggtt(vma));
 	GEM_BUG_ON(!i915_vma_is_bound(vma, I915_VMA_GLOBAL_BIND));
+	GEM_BUG_ON(i915_vma_verify_bind_complete(vma));
 
 	ptr = READ_ONCE(vma->iomap);
 	if (ptr == NULL) {
@@ -861,6 +895,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 		    u64 size, u64 alignment, u64 flags)
 {
 	struct i915_vma_work *work = NULL;
+	struct dma_fence *moving = NULL;
 	intel_wakeref_t wakeref = 0;
 	unsigned int bound;
 	int err;
@@ -886,7 +921,8 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 	if (flags & PIN_GLOBAL)
 		wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm);
 
-	if (flags & vma->vm->bind_async_flags) {
+	moving = vma->obj ? i915_gem_object_get_moving_fence(vma->obj) : NULL;
+	if (flags & vma->vm->bind_async_flags || moving) {
 		/* lock VM */
 		err = i915_vm_lock_objects(vma->vm, ww);
 		if (err)
@@ -900,6 +936,8 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 
 		work->vm = i915_vm_get(vma->vm);
 
+		dma_fence_work_chain(&work->base, moving);
+
 		/* Allocate enough page directories to used PTE */
 		if (vma->vm->allocate_va_range) {
 			err = i915_vm_alloc_pt_stash(vma->vm,
@@ -1004,7 +1042,10 @@ err_fence:
 err_rpm:
 	if (wakeref)
 		intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref);
+	if (moving)
+		dma_fence_put(moving);
 	vma_put_pages(vma);
+
 	return err;
 }