[Intel-xe] [PATCH] drm/xe/bo: Return object bo size on create

[Mauro Carvalho Chehab]

On Tue, 28 Mar 2023 15:08:26 +0200
Zbigniew Kempczyński <zbigniew.kempczynski at intel.com> wrote:

> Driver may alter bo size requested by the user. Return real object
> size to make userspace aware how to arrange vm bindings.
> 
> Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_bo.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index e4d079b61d52..410e797931ac 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -1564,6 +1564,7 @@ int xe_gem_create_ioctl(struct drm_device *dev, void *data,
>  		return err;
>  
>  	args->handle = handle;
> +	args->size = bo->size;
>  
>  	return 0;
>  }

An alternative approach would be instead to return -EINVAL if the
buffers aren't aligned. Something like this (untested) patch.

Regards,
Mauro

[PATCH] xe/xe_bo: Don't allow creating unaligned buffers

Ensure that bo will always be properly aligned.

Signed-off-by: Mauro Carvalho Chehab <mchehab at kernel.org>

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index f25257bbfc65..ecc04b887790 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -985,6 +985,7 @@ struct xe_bo *__xe_bo_create_locked(struct xe_device *xe, struct xe_bo *bo,
 	};
 	struct ttm_placement *placement;
 	uint32_t alignment;
+	size_t aligned_size;
 	int err;
 
 	/* Only kernel objects should set GT */
@@ -993,24 +994,28 @@ struct xe_bo *__xe_bo_create_locked(struct xe_device *xe, struct xe_bo *bo,
 	if (XE_WARN_ON(!size))
 		return ERR_PTR(-EINVAL);
 
-	if (!bo) {
-		bo = xe_bo_alloc();
-		if (IS_ERR(bo))
-			return bo;
-	}
-
-	bo->requested_size = size;
 	if (flags & (XE_BO_CREATE_VRAM0_BIT | XE_BO_CREATE_VRAM1_BIT |
 		     XE_BO_CREATE_STOLEN_BIT) &&
 	    !(flags & XE_BO_CREATE_IGNORE_MIN_PAGE_SIZE_BIT) &&
 	    xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K) {
-		size = ALIGN(size, SZ_64K);
+		aligned_size = ALIGN(size, SZ_64K);
 		flags |= XE_BO_INTERNAL_64K;
 		alignment = SZ_64K >> PAGE_SHIFT;
 	} else {
+		aligned_size = ALIGN(size, SZ_4K);
+		flags &= ~XE_BO_INTERNAL_64K;
 		alignment = SZ_4K >> PAGE_SHIFT;
 	}
 
+	if (aligned_size != size)
+		return ERR_PTR(-EINVAL);
+
+	if (!bo) {
+		bo = xe_bo_alloc();
+		if (IS_ERR(bo))
+			return bo;
+	}
+
 	bo->gt = gt;
 	bo->size = size;
 	bo->flags = flags;
diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
index a430d1568890..f8a55ef9e789 100644
--- a/drivers/gpu/drm/xe/xe_ggtt.c
+++ b/drivers/gpu/drm/xe/xe_ggtt.c
@@ -273,10 +273,8 @@ void xe_ggtt_map_bo(struct xe_ggtt *ggtt, struct xe_bo *bo)
 		xe_ggtt_set_pte(ggtt, start + offset, pte);
 	}
 
-	if (bo->size == bo->requested_size) {
-		pte = xe_ggtt_pte_encode(ggtt->scratch ?: bo, 0);
-		xe_ggtt_set_pte(ggtt, start + bo->size, pte);
-	}
+	pte = xe_ggtt_pte_encode(ggtt->scratch ?: bo, 0);
+	xe_ggtt_set_pte(ggtt, start + bo->size, pte);
 
 	if (ggtt->invalidate) {
 		xe_ggtt_invalidate(ggtt->gt);
@@ -309,11 +307,9 @@ static int __xe_ggtt_insert_bo_at(struct xe_ggtt *ggtt, struct xe_bo *bo,
 	 * fact we have programmed this GGTT entry to a valid entry. BO aligned
 	 * to 64k already have padding so no need to add an extra page.
 	 */
-	if (bo->size == bo->requested_size) {
-		size += SZ_4K;
-		if (end != U64_MAX)
-			end += SZ_4K;
-	}
+        size += alignment;
+        if (end != U64_MAX)
+                end += alignment;
 
 	mutex_lock(&ggtt->lock);
 	err = drm_mm_insert_node_in_range(&ggtt->mm, &bo->ggtt_node, size,