[PATCH v2 1/8] drm: Add dummy page per device or GEM object

[Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>]

Will be used to reroute CPU mapped BO's page faults once
device is removed.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
---
 drivers/gpu/drm/drm_file.c  |  8 ++++++++
 drivers/gpu/drm/drm_prime.c | 10 ++++++++++
 include/drm/drm_file.h      |  2 ++
 include/drm/drm_gem.h       |  2 ++
 4 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index c4c704e..67c0770 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -188,6 +188,12 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
 			goto out_prime_destroy;
 	}
 
+	file->dummy_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	if (!file->dummy_page) {
+		ret = -ENOMEM;
+		goto out_prime_destroy;
+	}
+
 	return file;
 
 out_prime_destroy:
@@ -284,6 +290,8 @@ void drm_file_free(struct drm_file *file)
 	if (dev->driver->postclose)
 		dev->driver->postclose(dev, file);
 
+	__free_page(file->dummy_page);
+
 	drm_prime_destroy_file_private(&file->prime);
 
 	WARN_ON(!list_empty(&file->event_list));
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1de2cde..c482e9c 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -335,6 +335,13 @@ int drm_gem_prime_fd_to_handle(struct drm_device *dev,
 
 	ret = drm_prime_add_buf_handle(&file_priv->prime,
 			dma_buf, *handle);
+
+	if (!ret) {
+		obj->dummy_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		if (!obj->dummy_page)
+			ret = -ENOMEM;
+	}
+
 	mutex_unlock(&file_priv->prime.lock);
 	if (ret)
 		goto fail;
@@ -1006,6 +1013,9 @@ void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg)
 		dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
 	dma_buf = attach->dmabuf;
 	dma_buf_detach(attach->dmabuf, attach);
+
+	__free_page(obj->dummy_page);
+
 	/* remove the reference */
 	dma_buf_put(dma_buf);
 }
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 19df802..349a658 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -335,6 +335,8 @@ struct drm_file {
 	 */
 	struct drm_prime_file_private prime;
 
+	struct page *dummy_page;
+
 	/* private: */
 #if IS_ENABLED(CONFIG_DRM_LEGACY)
 	unsigned long lock_count; /* DRI1 legacy lock count */
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 0b37506..47460d1 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -310,6 +310,8 @@ struct drm_gem_object {
 	 *
 	 */
 	const struct drm_gem_object_funcs *funcs;
+
+	struct page *dummy_page;
 };
 
 /**
-- 
2.7.4

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