[PATCH 09/10] drm/qxl: map/unmap framebuffers in prepare_fb+cleanup_fb callbacks.

We don't have to map in atomic_update callback then,
making locking a bit less complicated.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 drivers/gpu/drm/qxl/qxl_display.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
index 7500560db8e4..39b8c5116d34 100644
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c

@@ -584,7 +584,6 @@ static void qxl_cursor_atomic_update(struct drm_plane *plane,
 	struct drm_gem_object *obj;
 	struct qxl_bo *cursor_bo = NULL, *user_bo = NULL, *old_cursor_bo = NULL;
 	int ret;
-	struct dma_buf_map user_map;
 	struct dma_buf_map cursor_map;
 	void *user_ptr;
 	int size = 64*64*4;

@@ -599,11 +598,8 @@ static void qxl_cursor_atomic_update(struct drm_plane *plane,
 		obj = fb->obj[0];
 		user_bo = gem_to_qxl_bo(obj);
 
-		/* pinning is done in the prepare/cleanup framevbuffer */
-		ret = qxl_bo_kmap_locked(user_bo, &user_map);
-		if (ret)
-			goto out_free_release;
-		user_ptr = user_map.vaddr; /* TODO: Use mapping abstraction properly */
+		/* mapping is done in the prepare/cleanup framevbuffer */
+		user_ptr = user_bo->map.vaddr; /* TODO: Use mapping abstraction properly */
 
 		ret = qxl_alloc_bo_reserved(qdev, release,
 					    sizeof(struct qxl_cursor) + size,

@@ -639,7 +635,6 @@ static void qxl_cursor_atomic_update(struct drm_plane *plane,
 		cursor->chunk.data_size = size;
 		memcpy(cursor->chunk.data, user_ptr, size);
 		qxl_bo_kunmap_locked(cursor_bo);
-		qxl_bo_kunmap_locked(user_bo);
 
 		cmd = (struct qxl_cursor_cmd *) qxl_release_map(qdev, release);
 		cmd->u.set.visible = 1;

@@ -778,6 +773,7 @@ static int qxl_plane_prepare_fb(struct drm_plane *plane,
 	struct drm_gem_object *obj;
 	struct qxl_bo *user_bo;
 	struct qxl_surface surf;
+	struct dma_buf_map unused;
 
 	if (!new_state->fb)
 		return 0;

@@ -815,7 +811,7 @@ static int qxl_plane_prepare_fb(struct drm_plane *plane,
 		}
 	}
 
-	return qxl_bo_pin(user_bo);
+	return qxl_bo_kmap(user_bo, &unused);
 }
 
 static void qxl_plane_cleanup_fb(struct drm_plane *plane,

@@ -834,7 +830,7 @@ static void qxl_plane_cleanup_fb(struct drm_plane *plane,
 
 	obj = old_state->fb->obj[0];
 	user_bo = gem_to_qxl_bo(obj);
-	qxl_bo_unpin(user_bo);
+	qxl_bo_kunmap(user_bo);
 
 	if (old_state->fb != plane->state->fb && user_bo->shadow) {
 		qxl_bo_unpin(user_bo->shadow);

-- 
2.29.2

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Hi

this is a shadow-buffered plane. Did you consider using the new helpers 
for shadow-buffered planes? They will map the user BO for you and 
provide the mapping in the plane state.

 From there, you should implement your own plane state on top of struct 
drm_shadow_plane_state, and also move all the other allocations and 
vmaps into prepare_fb and cleanup_fb. Most of this is not actually 
allowed in commit tails. All we'd have to do is to export the reset, 
duplicate and destroy code; similar to what 
__drm_atomic_helper_plane_reset() does.

Best regards
Thomas


Am 16.02.21 um 12:37 schrieb Gerd Hoffmann:

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

Am 16.02.21 um 14:27 schrieb Thomas Zimmermann:

Hi

this is a shadow-buffered plane. Did you consider using the new helpers 
for shadow-buffered planes? They will map the user BO for you and 
provide the mapping in the plane state.

 From there, you should implement your own plane state on top of struct 
drm_shadow_plane_state, and also move all the other allocations and 
vmaps into prepare_fb and cleanup_fb. Most of this is not actually 
allowed in commit tails. All we'd have to do is to export the reset, 
duplicate and destroy code; similar to what 
__drm_atomic_helper_plane_reset() does.

AFAICT the cursor_bo is used to implement double buffering for the 
cursor image.

Ideally, you can do what ast does: pre-allocate/vmap 2 BOs at the end of 
the vram. Then pageflip between them in atomic_update(). Resolves all 
the allocation and mapping headaches.

Best regards
Thomas

Best regards
Thomas


Am 16.02.21 um 12:37 schrieb Gerd Hoffmann:

quoted

We don't have to map in atomic_update callback then,
making locking a bit less complicated.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
  drivers/gpu/drm/qxl/qxl_display.c | 14 +++++---------
  1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/qxl/qxl_display.c 

b/drivers/gpu/drm/qxl/qxl_display.c
index 7500560db8e4..39b8c5116d34 100644

--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c

@@ -584,7 +584,6 @@ static void qxl_cursor_atomic_update(struct 

drm_plane *plane,
      struct drm_gem_object *obj;
      struct qxl_bo *cursor_bo = NULL, *user_bo = NULL, *old_cursor_bo 
= NULL;
      int ret;
-    struct dma_buf_map user_map;
      struct dma_buf_map cursor_map;
      void *user_ptr;
      int size = 64*64*4;

@@ -599,11 +598,8 @@ static void qxl_cursor_atomic_update(struct 

drm_plane *plane,
          obj = fb->obj[0];
          user_bo = gem_to_qxl_bo(obj);
-        /* pinning is done in the prepare/cleanup framevbuffer */
-        ret = qxl_bo_kmap_locked(user_bo, &user_map);
-        if (ret)
-            goto out_free_release;
-        user_ptr = user_map.vaddr; /* TODO: Use mapping abstraction 
properly */
+        /* mapping is done in the prepare/cleanup framevbuffer */
+        user_ptr = user_bo->map.vaddr; /* TODO: Use mapping 
abstraction properly */
          ret = qxl_alloc_bo_reserved(qdev, release,
                          sizeof(struct qxl_cursor) + size,

@@ -639,7 +635,6 @@ static void qxl_cursor_atomic_update(struct 

drm_plane *plane,
          cursor->chunk.data_size = size;
          memcpy(cursor->chunk.data, user_ptr, size);
          qxl_bo_kunmap_locked(cursor_bo);
-        qxl_bo_kunmap_locked(user_bo);
          cmd = (struct qxl_cursor_cmd *) qxl_release_map(qdev, release);
          cmd->u.set.visible = 1;

@@ -778,6 +773,7 @@ static int qxl_plane_prepare_fb(struct drm_plane 

*plane,
      struct drm_gem_object *obj;
      struct qxl_bo *user_bo;
      struct qxl_surface surf;
+    struct dma_buf_map unused;
      if (!new_state->fb)
          return 0;

@@ -815,7 +811,7 @@ static int qxl_plane_prepare_fb(struct drm_plane 

*plane,
          }
      }
-    return qxl_bo_pin(user_bo);
+    return qxl_bo_kmap(user_bo, &unused);
  }
  static void qxl_plane_cleanup_fb(struct drm_plane *plane,

@@ -834,7 +830,7 @@ static void qxl_plane_cleanup_fb(struct drm_plane 

*plane,
      obj = old_state->fb->obj[0];
      user_bo = gem_to_qxl_bo(obj);
-    qxl_bo_unpin(user_bo);
+    qxl_bo_kunmap(user_bo);
      if (old_state->fb != plane->state->fb && user_bo->shadow) {
          qxl_bo_unpin(user_bo->shadow);

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-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

On Tue, Feb 16, 2021 at 02:46:21PM +0100, Thomas Zimmermann wrote:

Am 16.02.21 um 14:27 schrieb Thomas Zimmermann:

quoted

Hi

this is a shadow-buffered plane. Did you consider using the new helpers
for shadow-buffered planes? They will map the user BO for you and
provide the mapping in the plane state.

 From there, you should implement your own plane state on top of struct
drm_shadow_plane_state, and also move all the other allocations and
vmaps into prepare_fb and cleanup_fb. Most of this is not actually
allowed in commit tails. All we'd have to do is to export the reset,
duplicate and destroy code; similar to what
__drm_atomic_helper_plane_reset() does.

AFAICT the cursor_bo is used to implement double buffering for the cursor
image.

Ideally, you can do what ast does: pre-allocate/vmap 2 BOs at the end of the
vram. Then pageflip between them in atomic_update(). Resolves all the
allocation and mapping headaches.

Just waded through the ast patches.

It is not that simple for qxl.  You have to send a command to the
virtualization host and take care of the host accessing that memory
when processing the command, so you can't reuse the memory until the
host signals it is fine to do so.

But, yes, it should be possible to handle cursor_bo creation in
prepare_fb without too much effort.

take care,
  Gerd

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Virtualization@lists.linux-foundation.org
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Hi

Am 17.02.21 um 11:02 schrieb Gerd Hoffmann:

On Tue, Feb 16, 2021 at 02:46:21PM +0100, Thomas Zimmermann wrote:

quoted

Am 16.02.21 um 14:27 schrieb Thomas Zimmermann:

quoted

Hi

this is a shadow-buffered plane. Did you consider using the new helpers
for shadow-buffered planes? They will map the user BO for you and
provide the mapping in the plane state.

  From there, you should implement your own plane state on top of struct
drm_shadow_plane_state, and also move all the other allocations and
vmaps into prepare_fb and cleanup_fb. Most of this is not actually
allowed in commit tails. All we'd have to do is to export the reset,
duplicate and destroy code; similar to what
__drm_atomic_helper_plane_reset() does.

AFAICT the cursor_bo is used to implement double buffering for the cursor
image.

Ideally, you can do what ast does: pre-allocate/vmap 2 BOs at the end of the
vram. Then pageflip between them in atomic_update(). Resolves all the
allocation and mapping headaches.

Just waded through the ast patches.

I just received your ack. Thanks a lot for looking at the ast patches.

It is not that simple for qxl.  You have to send a command to the
virtualization host and take care of the host accessing that memory
when processing the command, so you can't reuse the memory until the
host signals it is fine to do so.

But, yes, it should be possible to handle cursor_bo creation in
prepare_fb without too much effort.

I've been thinking about this issue and here's an idea:

If you take the ast code as a blueprint, you'd store two cursor bo in a 
cursor-plane structure. Aditionally each of these BOs would have a 
pointer to a fence associated with it.

One idea for the fencing code would be to allocate each new fence in 
prepare_fb and store it in the cursor plane state. In atomic_update, 
pick the unused BO in the cursor plane and wait on its fence. This 
should guarantee that the BO is available. (?) Then swap the BO's fence 
with the one in the cursor plane state. Setup the new fence for 
synchronization with the host. Next time you pick this cursor BO, the 
fence will be there for synchronization. The old fence from the cursor 
BO will now be stored in the cursor-plane state and can be freed in 
cleanup_fb().

My main interest here is to move all fail-able/locking calls out of the 
atomic_update function. I might be missing some crucial corner case, but 
this should resolve the issue. (?) In any case, it's maybe worth a 
separate patchset.

Best regards
Thomas

take care,
   Gerd

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-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer