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From:   Gerd Hoffmann <kraxel@redhat.com>
To:     dri-devel@lists.freedesktop.org
Cc:     olvaffe@gmail.com, gurchetansingh@chromium.org,
        Gerd Hoffmann <kraxel@redhat.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        virtualization@lists.linux-foundation.org (open list:VIRTIO GPU DRIVER),
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v2] drm/virtio: rework batching
Date:   Wed, 12 Feb 2020 12:12:45 +0100
Message-Id: <20200212111246.12563-1-kraxel@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Drop the virtio_gpu_{disable,enable}_notify().  Add a new
virtio_gpu_notify() call instead, which must be called whenever
the driver wants make sure the host is notified needed.

Drop notification from command submission.  Add virtio_gpu_notify()
calls everywhere instead.  This results in more batching because we now
notify only once for a series of commands.  We already had that for page
flips, now we also batch resource creation (create + attach-backing),
display updates (edid + display-info) and device initialization.  With
this in place it is also possible to make notification optional for
userspace ioctls.

v2:
 - rebase to latest drm-misc-next.
 - use "if (!atomic_read())".
 - add review & test tags.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
---
 drivers/gpu/drm/virtio/virtgpu_drv.h     |  6 ++---
 drivers/gpu/drm/virtio/virtgpu_display.c |  2 ++
 drivers/gpu/drm/virtio/virtgpu_ioctl.c   |  4 ++++
 drivers/gpu/drm/virtio/virtgpu_kms.c     |  3 +++
 drivers/gpu/drm/virtio/virtgpu_object.c  |  1 +
 drivers/gpu/drm/virtio/virtgpu_plane.c   |  5 ++--
 drivers/gpu/drm/virtio/virtgpu_vq.c      | 30 ++++++++++--------------
 7 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index af9403e1cf78..2f6c4ccbfd14 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -179,8 +179,7 @@ struct virtio_gpu_device {
 	struct virtio_gpu_queue cursorq;
 	struct kmem_cache *vbufs;
 
-	bool disable_notify;
-	bool pending_notify;
+	atomic_t pending_commands;
 
 	struct ida	resource_ida;
 
@@ -335,8 +334,7 @@ void virtio_gpu_dequeue_ctrl_func(struct work_struct *work);
 void virtio_gpu_dequeue_cursor_func(struct work_struct *work);
 void virtio_gpu_dequeue_fence_func(struct work_struct *work);
 
-void virtio_gpu_disable_notify(struct virtio_gpu_device *vgdev);
-void virtio_gpu_enable_notify(struct virtio_gpu_device *vgdev);
+void virtio_gpu_notify(struct virtio_gpu_device *vgdev);
 
 /* virtio_gpu_display.c */
 void virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev);
diff --git a/drivers/gpu/drm/virtio/virtgpu_display.c b/drivers/gpu/drm/virtio/virtgpu_display.c
index af953db4a0c9..2b7e6ae65546 100644
--- a/drivers/gpu/drm/virtio/virtgpu_display.c
+++ b/drivers/gpu/drm/virtio/virtgpu_display.c
@@ -90,6 +90,7 @@ static void virtio_gpu_crtc_mode_set_nofb(struct drm_crtc *crtc)
 	virtio_gpu_cmd_set_scanout(vgdev, output->index, 0,
 				   crtc->mode.hdisplay,
 				   crtc->mode.vdisplay, 0, 0);
+	virtio_gpu_notify(vgdev);
 }
 
 static void virtio_gpu_crtc_atomic_enable(struct drm_crtc *crtc,
@@ -108,6 +109,7 @@ static void virtio_gpu_crtc_atomic_disable(struct drm_crtc *crtc,
 	struct virtio_gpu_output *output = drm_crtc_to_virtio_gpu_output(crtc);
 
 	virtio_gpu_cmd_set_scanout(vgdev, output->index, 0, 0, 0, 0, 0);
+	virtio_gpu_notify(vgdev);
 	output->enabled = false;
 }
 
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 205ec4abae2b..75d818d707e6 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -158,6 +158,7 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 
 	virtio_gpu_cmd_submit(vgdev, buf, exbuf->size,
 			      vfpriv->ctx_id, buflist, out_fence);
+	virtio_gpu_notify(vgdev);
 	return 0;
 
 out_memdup:
@@ -314,6 +315,7 @@ static int virtio_gpu_transfer_from_host_ioctl(struct drm_device *dev,
 		(vgdev, vfpriv->ctx_id, offset, args->level,
 		 &args->box, objs, fence);
 	dma_fence_put(&fence->f);
+	virtio_gpu_notify(vgdev);
 	return 0;
 
 err_unlock:
@@ -359,6 +361,7 @@ static int virtio_gpu_transfer_to_host_ioctl(struct drm_device *dev, void *data,
 			 args->level, &args->box, objs, fence);
 		dma_fence_put(&fence->f);
 	}
+	virtio_gpu_notify(vgdev);
 	return 0;
 
 err_unlock:
@@ -445,6 +448,7 @@ static int virtio_gpu_get_caps_ioctl(struct drm_device *dev,
 	/* not in cache - need to talk to hw */
 	virtio_gpu_cmd_get_capset(vgdev, found_valid, args->cap_set_ver,
 				  &cache_ent);
+	virtio_gpu_notify(vgdev);
 
 copy_exit:
 	ret = wait_event_timeout(vgdev->resp_wq,
diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
index 4009c2f97d08..7eabcf1ca424 100644
--- a/drivers/gpu/drm/virtio/virtgpu_kms.c
+++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
@@ -44,6 +44,7 @@ static void virtio_gpu_config_changed_work_func(struct work_struct *work)
 		if (vgdev->has_edid)
 			virtio_gpu_cmd_get_edids(vgdev);
 		virtio_gpu_cmd_get_display_info(vgdev);
+		virtio_gpu_notify(vgdev);
 		drm_helper_hpd_irq_event(vgdev->ddev);
 		events_clear |= VIRTIO_GPU_EVENT_DISPLAY;
 	}
@@ -92,6 +93,7 @@ static void virtio_gpu_get_capsets(struct virtio_gpu_device *vgdev,
 	}
 	for (i = 0; i < num_capsets; i++) {
 		virtio_gpu_cmd_get_capset_info(vgdev, i);
+		virtio_gpu_notify(vgdev);
 		ret = wait_event_timeout(vgdev->resp_wq,
 					 vgdev->capsets[i].id > 0, 5 * HZ);
 		if (ret == 0) {
@@ -205,6 +207,7 @@ int virtio_gpu_init(struct drm_device *dev)
 	if (vgdev->has_edid)
 		virtio_gpu_cmd_get_edids(vgdev);
 	virtio_gpu_cmd_get_display_info(vgdev);
+	virtio_gpu_notify(vgdev);
 	wait_event_timeout(vgdev->resp_wq, !vgdev->display_info_pending,
 			   5 * HZ);
 	return 0;
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index 8870ee23ff2b..65d6834d3c74 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -224,6 +224,7 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 		return ret;
 	}
 
+	virtio_gpu_notify(vgdev);
 	*bo_ptr = bo;
 	return 0;
 
diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
index ac42c84d2d7f..fd6487fb0855 100644
--- a/drivers/gpu/drm/virtio/virtgpu_plane.c
+++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
@@ -154,8 +154,6 @@ static void virtio_gpu_primary_plane_update(struct drm_plane *plane,
 	if (!drm_atomic_helper_damage_merged(old_state, plane->state, &rect))
 		return;
 
-	virtio_gpu_disable_notify(vgdev);
-
 	bo = gem_to_virtio_gpu_obj(plane->state->fb->obj[0]);
 	if (bo->dumb)
 		virtio_gpu_update_dumb_bo(vgdev, plane->state, &rect);
@@ -187,7 +185,7 @@ static void virtio_gpu_primary_plane_update(struct drm_plane *plane,
 				      rect.x2 - rect.x1,
 				      rect.y2 - rect.y1);
 
-	virtio_gpu_enable_notify(vgdev);
+	virtio_gpu_notify(vgdev);
 }
 
 static int virtio_gpu_cursor_prepare_fb(struct drm_plane *plane,
@@ -265,6 +263,7 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane,
 			 plane->state->crtc_w,
 			 plane->state->crtc_h,
 			 0, 0, objs, vgfb->fence);
+		virtio_gpu_notify(vgdev);
 		dma_fence_wait(&vgfb->fence->f, true);
 		dma_fence_put(&vgfb->fence->f);
 		vgfb->fence = NULL;
diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index cfe9c54f87a3..357fef8197dc 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -329,7 +329,6 @@ static void virtio_gpu_queue_ctrl_sgs(struct virtio_gpu_device *vgdev,
 				      int incnt)
 {
 	struct virtqueue *vq = vgdev->ctrlq.vq;
-	bool notify = false;
 	int ret, idx;
 
 	if (!drm_dev_enter(vgdev->ddev, &idx)) {
@@ -368,16 +367,10 @@ static void virtio_gpu_queue_ctrl_sgs(struct virtio_gpu_device *vgdev,
 
 	trace_virtio_gpu_cmd_queue(vq, virtio_gpu_vbuf_ctrl_hdr(vbuf));
 
-	notify = virtqueue_kick_prepare(vq);
+	atomic_inc(&vgdev->pending_commands);
 
 	spin_unlock(&vgdev->ctrlq.qlock);
 
-	if (notify) {
-		if (vgdev->disable_notify)
-			vgdev->pending_notify = true;
-		else
-			virtqueue_notify(vq);
-	}
 	drm_dev_exit(idx);
 }
 
@@ -434,19 +427,20 @@ static void virtio_gpu_queue_fenced_ctrl_buffer(struct virtio_gpu_device *vgdev,
 	}
 }
 
-void virtio_gpu_disable_notify(struct virtio_gpu_device *vgdev)
+void virtio_gpu_notify(struct virtio_gpu_device *vgdev)
 {
-	vgdev->disable_notify = true;
-}
+	bool notify;
 
-void virtio_gpu_enable_notify(struct virtio_gpu_device *vgdev)
-{
-	vgdev->disable_notify = false;
-
-	if (!vgdev->pending_notify)
+	if (!atomic_read(&vgdev->pending_commands))
 		return;
-	vgdev->pending_notify = false;
-	virtqueue_notify(vgdev->ctrlq.vq);
+
+	spin_lock(&vgdev->ctrlq.qlock);
+	atomic_set(&vgdev->pending_commands, 0);
+	notify = virtqueue_kick_prepare(vgdev->ctrlq.vq);
+	spin_unlock(&vgdev->ctrlq.qlock);
+
+	if (notify)
+		virtqueue_notify(vgdev->ctrlq.vq);
 }
 
 static void virtio_gpu_queue_ctrl_buffer(struct virtio_gpu_device *vgdev,
-- 
2.18.2