drm/vgem: Attach sw fences to exported vGEM dma-buf (ioctl)

ickle · danvet · commit 407779848445 · 2016-07-18T08:54:55.000+02:00
vGEM buffers are useful for passing data between software clients and hardware renders. By allowing the user to create and attach fences to the exported vGEM buffers (on the dma-buf), the user can implement a deferred renderer and queue hardware operations like flipping and then signal the buffer readiness (i.e. this allows the user to schedule operations out-of-order, but have them complete in-order). This also makes it much easier to write tightly controlled testcases for dma-buf fencing and signaling between hardware drivers. v2: Don't pretend the fences exist in an ordered timeline, but allocate a separate fence-context for each fence so that the fences are unordered. v3: Make the debug output more interesting, and show the signaled status. v4: Automatically signal the fence to prevent userspace from indefinitely hanging drivers. Testcase: igt/vgem_basic/dmabuf-fence Testcase: igt/vgem_slow/nohang Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Sean Paul <seanpaul@chromium.org> Cc: Zach Reizner <zachr@google.com> Cc: Gustavo Padovan <gustavo.padovan@collabora.co.uk> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Zach Reizner <zachr@google.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1468571471-12610-1-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/vgem/Makefile b/drivers/gpu/drm/vgem/Makefile
@@ -1,4 +1,4 @@
 ccflags-y := -Iinclude/drm
-vgem-y := vgem_drv.o
+vgem-y := vgem_drv.o vgem_fence.o
 
 obj-$(CONFIG_DRM_VGEM)	+= vgem.o
diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -83,6 +83,34 @@ static const struct vm_operations_struct vgem_gem_vm_ops = {
 	.close = drm_gem_vm_close,
 };
 
+static int vgem_open(struct drm_device *dev, struct drm_file *file)
+{
+	struct vgem_file *vfile;
+	int ret;
+
+	vfile = kzalloc(sizeof(*vfile), GFP_KERNEL);
+	if (!vfile)
+		return -ENOMEM;
+
+	file->driver_priv = vfile;
+
+	ret = vgem_fence_open(vfile);
+	if (ret) {
+		kfree(vfile);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void vgem_preclose(struct drm_device *dev, struct drm_file *file)
+{
+	struct vgem_file *vfile = file->driver_priv;
+
+	vgem_fence_close(vfile);
+	kfree(vfile);
+}
+
 /* ioctls */
 
 static struct drm_gem_object *vgem_gem_create(struct drm_device *dev,
@@ -164,6 +192,8 @@ static int vgem_gem_dumb_map(struct drm_file *file, struct drm_device *dev,
 }
 
 static struct drm_ioctl_desc vgem_ioctls[] = {
+	DRM_IOCTL_DEF_DRV(VGEM_FENCE_ATTACH, vgem_fence_attach_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF_DRV(VGEM_FENCE_SIGNAL, vgem_fence_signal_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
 };
 
 static int vgem_mmap(struct file *filp, struct vm_area_struct *vma)
@@ -271,9 +301,12 @@ static int vgem_prime_mmap(struct drm_gem_object *obj,
 
 static struct drm_driver vgem_driver = {
 	.driver_features		= DRIVER_GEM | DRIVER_PRIME,
+	.open				= vgem_open,
+	.preclose			= vgem_preclose,
 	.gem_free_object_unlocked	= vgem_gem_free_object,
 	.gem_vm_ops			= &vgem_gem_vm_ops,
 	.ioctls				= vgem_ioctls,
+	.num_ioctls 			= ARRAY_SIZE(vgem_ioctls),
 	.fops				= &vgem_driver_fops,
 
 	.dumb_create			= vgem_gem_dumb_create,
@@ -328,5 +361,6 @@ module_init(vgem_init);
 module_exit(vgem_exit);
 
 MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_AUTHOR("Intel Corporation");
 MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_LICENSE("GPL and additional rights");
diff --git a/drivers/gpu/drm/vgem/vgem_drv.h b/drivers/gpu/drm/vgem/vgem_drv.h
@@ -32,9 +32,25 @@
 #include <drm/drmP.h>
 #include <drm/drm_gem.h>
 
+#include <uapi/drm/vgem_drm.h>
+
+struct vgem_file {
+	struct idr fence_idr;
+	struct mutex fence_mutex;
+};
+
 #define to_vgem_bo(x) container_of(x, struct drm_vgem_gem_object, base)
 struct drm_vgem_gem_object {
 	struct drm_gem_object base;
 };
 
+int vgem_fence_open(struct vgem_file *file);
+int vgem_fence_attach_ioctl(struct drm_device *dev,
+			    void *data,
+			    struct drm_file *file);
+int vgem_fence_signal_ioctl(struct drm_device *dev,
+			    void *data,
+			    struct drm_file *file);
+void vgem_fence_close(struct vgem_file *file);
+
 #endif
diff --git a/drivers/gpu/drm/vgem/vgem_fence.c b/drivers/gpu/drm/vgem/vgem_fence.c
@@ -0,0 +1,283 @@
+/*
+ * Copyright 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software")
+ * to deal in the software without restriction, including without limitation
+ * on the rights to use, copy, modify, merge, publish, distribute, sub
+ * license, and/or sell copies of the Software, and to permit persons to whom
+ * them Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTIBILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES, OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT, OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/reservation.h>
+
+#include "vgem_drv.h"
+
+#define VGEM_FENCE_TIMEOUT (10*HZ)
+
+struct vgem_fence {
+	struct fence base;
+	struct spinlock lock;
+	struct timer_list timer;
+};
+
+static const char *vgem_fence_get_driver_name(struct fence *fence)
+{
+	return "vgem";
+}
+
+static const char *vgem_fence_get_timeline_name(struct fence *fence)
+{
+	return "unbound";
+}
+
+static bool vgem_fence_signaled(struct fence *fence)
+{
+	return false;
+}
+
+static bool vgem_fence_enable_signaling(struct fence *fence)
+{
+	return true;
+}
+
+static void vgem_fence_release(struct fence *base)
+{
+	struct vgem_fence *fence = container_of(base, typeof(*fence), base);
+
+	del_timer_sync(&fence->timer);
+	fence_free(&fence->base);
+}
+
+static void vgem_fence_value_str(struct fence *fence, char *str, int size)
+{
+	snprintf(str, size, "%u", fence->seqno);
+}
+
+static void vgem_fence_timeline_value_str(struct fence *fence, char *str,
+					  int size)
+{
+	snprintf(str, size, "%u", fence_is_signaled(fence) ? fence->seqno : 0);
+}
+
+const struct fence_ops vgem_fence_ops = {
+	.get_driver_name = vgem_fence_get_driver_name,
+	.get_timeline_name = vgem_fence_get_timeline_name,
+	.enable_signaling = vgem_fence_enable_signaling,
+	.signaled = vgem_fence_signaled,
+	.wait = fence_default_wait,
+	.release = vgem_fence_release,
+
+	.fence_value_str = vgem_fence_value_str,
+	.timeline_value_str = vgem_fence_timeline_value_str,
+};
+
+static void vgem_fence_timeout(unsigned long data)
+{
+	struct vgem_fence *fence = (struct vgem_fence *)data;
+
+	fence_signal(&fence->base);
+}
+
+static struct fence *vgem_fence_create(struct vgem_file *vfile,
+				       unsigned int flags)
+{
+	struct vgem_fence *fence;
+
+	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
+	if (!fence)
+		return NULL;
+
+	spin_lock_init(&fence->lock);
+	fence_init(&fence->base, &vgem_fence_ops, &fence->lock,
+		   fence_context_alloc(1), 1);
+
+	setup_timer(&fence->timer, vgem_fence_timeout, (unsigned long)fence);
+
+	/* We force the fence to expire within 10s to prevent driver hangs */
+	mod_timer(&fence->timer, VGEM_FENCE_TIMEOUT);
+
+	return &fence->base;
+}
+
+static int attach_dmabuf(struct drm_device *dev,
+			 struct drm_gem_object *obj)
+{
+	struct dma_buf *dmabuf;
+
+	if (obj->dma_buf)
+		return 0;
+
+	dmabuf = dev->driver->gem_prime_export(dev, obj, 0);
+	if (IS_ERR(dmabuf))
+		return PTR_ERR(dmabuf);
+
+	obj->dma_buf = dmabuf;
+	drm_gem_object_reference(obj);
+	return 0;
+}
+
+/*
+ * vgem_fence_attach_ioctl (DRM_IOCTL_VGEM_FENCE_ATTACH):
+ *
+ * Create and attach a fence to the vGEM handle. This fence is then exposed
+ * via the dma-buf reservation object and visible to consumers of the exported
+ * dma-buf. If the flags contain VGEM_FENCE_WRITE, the fence indicates the
+ * vGEM buffer is being written to by the client and is exposed as an exclusive
+ * fence, otherwise the fence indicates the client is current reading from the
+ * buffer and all future writes should wait for the client to signal its
+ * completion. Note that if a conflicting fence is already on the dma-buf (i.e.
+ * an exclusive fence when adding a read, or any fence when adding a write),
+ * -EBUSY is reported. Serialisation between operations should be handled
+ * by waiting upon the dma-buf.
+ *
+ * This returns the handle for the new fence that must be signaled within 10
+ * seconds (or otherwise it will automatically expire). See
+ * vgem_fence_signal_ioctl (DRM_IOCTL_VGEM_FENCE_SIGNAL).
+ *
+ * If the vGEM handle does not exist, vgem_fence_attach_ioctl returns -ENOENT.
+ */
+int vgem_fence_attach_ioctl(struct drm_device *dev,
+			    void *data,
+			    struct drm_file *file)
+{
+	struct drm_vgem_fence_attach *arg = data;
+	struct vgem_file *vfile = file->driver_priv;
+	struct reservation_object *resv;
+	struct drm_gem_object *obj;
+	struct fence *fence;
+	int ret;
+
+	if (arg->flags & ~VGEM_FENCE_WRITE)
+		return -EINVAL;
+
+	if (arg->pad)
+		return -EINVAL;
+
+	obj = drm_gem_object_lookup(file, arg->handle);
+	if (!obj)
+		return -ENOENT;
+
+	ret = attach_dmabuf(dev, obj);
+	if (ret)
+		goto err;
+
+	fence = vgem_fence_create(vfile, arg->flags);
+	if (!fence) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	/* Check for a conflicting fence */
+	resv = obj->dma_buf->resv;
+	if (!reservation_object_test_signaled_rcu(resv,
+						  arg->flags & VGEM_FENCE_WRITE)) {
+		ret = -EBUSY;
+		goto err_fence;
+	}
+
+	/* Expose the fence via the dma-buf */
+	ret = 0;
+	mutex_lock(&resv->lock.base);
+	if (arg->flags & VGEM_FENCE_WRITE)
+		reservation_object_add_excl_fence(resv, fence);
+	else if ((ret = reservation_object_reserve_shared(resv)) == 0)
+		reservation_object_add_shared_fence(resv, fence);
+	mutex_unlock(&resv->lock.base);
+
+	/* Record the fence in our idr for later signaling */
+	if (ret == 0) {
+		mutex_lock(&vfile->fence_mutex);
+		ret = idr_alloc(&vfile->fence_idr, fence, 1, 0, GFP_KERNEL);
+		mutex_unlock(&vfile->fence_mutex);
+		if (ret > 0) {
+			arg->out_fence = ret;
+			ret = 0;
+		}
+	}
+err_fence:
+	if (ret) {
+		fence_signal(fence);
+		fence_put(fence);
+	}
+err:
+	drm_gem_object_unreference_unlocked(obj);
+	return ret;
+}
+
+/*
+ * vgem_fence_signal_ioctl (DRM_IOCTL_VGEM_FENCE_SIGNAL):
+ *
+ * Signal and consume a fence ealier attached to a vGEM handle using
+ * vgem_fence_attach_ioctl (DRM_IOCTL_VGEM_FENCE_ATTACH).
+ *
+ * All fences must be signaled within 10s of attachment or otherwise they
+ * will automatically expire (and a vgem_fence_signal_ioctl returns -ETIMEDOUT).
+ *
+ * Signaling a fence indicates to all consumers of the dma-buf that the
+ * client has completed the operation associated with the fence, and that the
+ * buffer is then ready for consumption.
+ *
+ * If the fence does not exist (or has already been signaled by the client),
+ * vgem_fence_signal_ioctl returns -ENOENT.
+ */
+int vgem_fence_signal_ioctl(struct drm_device *dev,
+			    void *data,
+			    struct drm_file *file)
+{
+	struct vgem_file *vfile = file->driver_priv;
+	struct drm_vgem_fence_signal *arg = data;
+	struct fence *fence;
+	int ret;
+
+	if (arg->flags)
+		return -EINVAL;
+
+	mutex_lock(&vfile->fence_mutex);
+	fence = idr_replace(&vfile->fence_idr, NULL, arg->fence);
+	mutex_unlock(&vfile->fence_mutex);
+	if (!fence)
+		return -ENOENT;
+	if (IS_ERR(fence))
+		return PTR_ERR(fence);
+
+	if (fence_is_signaled(fence))
+		ret = -ETIMEDOUT;
+
+	fence_signal(fence);
+	fence_put(fence);
+	return ret;
+}
+
+int vgem_fence_open(struct vgem_file *vfile)
+{
+	mutex_init(&vfile->fence_mutex);
+	idr_init(&vfile->fence_idr);
+
+	return 0;
+}
+
+static int __vgem_fence_idr_fini(int id, void *p, void *data)
+{
+	fence_signal(p);
+	fence_put(p);
+	return 0;
+}
+
+void vgem_fence_close(struct vgem_file *vfile)
+{
+	idr_for_each(&vfile->fence_idr, __vgem_fence_idr_fini, vfile);
+	idr_destroy(&vfile->fence_idr);
+}
diff --git a/include/uapi/drm/vgem_drm.h b/include/uapi/drm/vgem_drm.h
