drm/i915: Add support for drm syncobjs

This commit adds support for waiting on or signaling DRM syncobjs as
part of execbuf.  It does so by hijacking the currently unused cliprects
pointer to instead point to an array of i915_gem_exec_fence structs
which containe a DRM syncobj and a flags parameter which specifies
whether to wait on it or to signal it.  This implementation
theoretically allows for both flags to be set in which case it waits on
the dma_fence that was in the syncobj and then immediately replaces it
with the dma_fence from the current execbuf.

v2:
 - Rebase on new syncobj API
v3:
 - Pull everything out into helpers
 - Do all allocation in gem_execbuffer2
 - Pack the flags in the bottom 2 bits of the drm_syncobj*
v4:
 - Prevent a potential race on syncobj->fence

Testcase: igt/gem_exec_fence/syncobj*
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/1499289202-25441-1-git-send-email-jason.ekstrand@intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170815145733.4562-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.c

@@ -388,6 +388,7 @@ static int i915_getparam(struct drm_device *dev, void *data,
 	case I915_PARAM_HAS_EXEC_FENCE:
 	case I915_PARAM_HAS_EXEC_CAPTURE:
 	case I915_PARAM_HAS_EXEC_BATCH_FIRST:
+	case I915_PARAM_HAS_EXEC_FENCE_ARRAY:
 		/* For the time being all of these are always true;
 		 * if some supported hardware does not have one of these
 		 * features this value needs to be provided from
@@ -2739,7 +2740,7 @@ static struct drm_driver driver = {
 	 */
 	.driver_features =
 	    DRIVER_HAVE_IRQ | DRIVER_IRQ_SHARED | DRIVER_GEM | DRIVER_PRIME |
-	    DRIVER_RENDER | DRIVER_MODESET | DRIVER_ATOMIC,
+	    DRIVER_RENDER | DRIVER_MODESET | DRIVER_ATOMIC | DRIVER_SYNCOBJ,
 	.release = i915_driver_release,
 	.open = i915_driver_open,
 	.lastclose = i915_driver_lastclose,

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -32,6 +32,7 @@
 #include <linux/uaccess.h>
 
 #include <drm/drmP.h>
+#include <drm/drm_syncobj.h>
 #include <drm/i915_drm.h>
 
 #include "i915_drv.h"
@@ -1896,8 +1897,10 @@ static bool i915_gem_check_execbuffer(struct drm_i915_gem_execbuffer2 *exec)
 		return false;
 
 	/* Kernel clipping was a DRI1 misfeature */
+	if (!(exec->flags & I915_EXEC_FENCE_ARRAY)) {
 		if (exec->num_cliprects || exec->cliprects_ptr)
 			return false;
+	}
 
 	if (exec->DR4 == 0xffffffff) {
 		DRM_DEBUG("UXA submitting garbage DR4, fixing up\n");
@@ -2128,11 +2131,131 @@ eb_select_engine(struct drm_i915_private *dev_priv,
 	return engine;
 }
 
+static void
+__free_fence_array(struct drm_syncobj **fences, unsigned int n)
+{
+	while (n--)
+		drm_syncobj_put(ptr_mask_bits(fences[n], 2));
+	kvfree(fences);
+}
+
+static struct drm_syncobj **
+get_fence_array(struct drm_i915_gem_execbuffer2 *args,
+		struct drm_file *file)
+{
+	const unsigned int nfences = args->num_cliprects;
+	struct drm_i915_gem_exec_fence __user *user;
+	struct drm_syncobj **fences;
+	unsigned int n;
+	int err;
+
+	if (!(args->flags & I915_EXEC_FENCE_ARRAY))
+		return NULL;
+
+	if (nfences > SIZE_MAX / sizeof(*fences))
+		return ERR_PTR(-EINVAL);
+
+	user = u64_to_user_ptr(args->cliprects_ptr);
+	if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
+		return ERR_PTR(-EFAULT);
+
+	fences = kvmalloc_array(args->num_cliprects, sizeof(*fences),
+				__GFP_NOWARN | GFP_TEMPORARY);
+	if (!fences)
+		return ERR_PTR(-ENOMEM);
+
+	for (n = 0; n < nfences; n++) {
+		struct drm_i915_gem_exec_fence fence;
+		struct drm_syncobj *syncobj;
+
+		if (__copy_from_user(&fence, user++, sizeof(fence))) {
+			err = -EFAULT;
+			goto err;
+		}
+
+		syncobj = drm_syncobj_find(file, fence.handle);
+		if (!syncobj) {
+			DRM_DEBUG("Invalid syncobj handle provided\n");
+			err = -ENOENT;
+			goto err;
+		}
+
+		fences[n] = ptr_pack_bits(syncobj, fence.flags, 2);
+	}
+
+	return fences;
+
+err:
+	__free_fence_array(fences, n);
+	return ERR_PTR(err);
+}
+
+static void
+put_fence_array(struct drm_i915_gem_execbuffer2 *args,
+		struct drm_syncobj **fences)
+{
+	if (fences)
+		__free_fence_array(fences, args->num_cliprects);
+}
+
+static int
+await_fence_array(struct i915_execbuffer *eb,
+		  struct drm_syncobj **fences)
+{
+	const unsigned int nfences = eb->args->num_cliprects;
+	unsigned int n;
+	int err;
+
+	for (n = 0; n < nfences; n++) {
+		struct drm_syncobj *syncobj;
+		struct dma_fence *fence;
+		unsigned int flags;
+
+		syncobj = ptr_unpack_bits(fences[n], &flags, 2);
+		if (!(flags & I915_EXEC_FENCE_WAIT))
+			continue;
+
+		rcu_read_lock();
+		fence = dma_fence_get_rcu_safe(&syncobj->fence);
+		rcu_read_unlock();
+		if (!fence)
+			return -EINVAL;
+
+		err = i915_gem_request_await_dma_fence(eb->request, fence);
+		dma_fence_put(fence);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+static void
+signal_fence_array(struct i915_execbuffer *eb,
+		   struct drm_syncobj **fences)
+{
+	const unsigned int nfences = eb->args->num_cliprects;
+	struct dma_fence * const fence = &eb->request->fence;
+	unsigned int n;
+
+	for (n = 0; n < nfences; n++) {
+		struct drm_syncobj *syncobj;
+		unsigned int flags;
+
+		syncobj = ptr_unpack_bits(fences[n], &flags, 2);
+		if (!(flags & I915_EXEC_FENCE_SIGNAL))
+			continue;
+
+		drm_syncobj_replace_fence(syncobj, fence);
+	}
+}
+
 static int
 i915_gem_do_execbuffer(struct drm_device *dev,
 		       struct drm_file *file,
 		       struct drm_i915_gem_execbuffer2 *args,
-		       struct drm_i915_gem_exec_object2 *exec)
+		       struct drm_i915_gem_exec_object2 *exec,
+		       struct drm_syncobj **fences)
 {
 	struct i915_execbuffer eb;
 	struct dma_fence *in_fence = NULL;
@@ -2318,6 +2441,12 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 			goto err_request;
 	}
 
+	if (fences) {
+		err = await_fence_array(&eb, fences);
+		if (err)
+			goto err_request;
+	}
+
 	if (out_fence_fd != -1) {
 		out_fence = sync_file_create(&eb.request->fence);
 		if (!out_fence) {
@@ -2341,6 +2470,9 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	__i915_add_request(eb.request, err == 0);
 	add_to_client(eb.request, file);
 
+	if (fences)
+		signal_fence_array(&eb, fences);
+
 	if (out_fence) {
 		if (err == 0) {
 			fd_install(out_fence_fd, out_fence->file);
@@ -2442,7 +2574,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
 			exec2_list[i].flags = 0;
 	}
 
-	err = i915_gem_do_execbuffer(dev, file, &exec2, exec2_list);
+	err = i915_gem_do_execbuffer(dev, file, &exec2, exec2_list, NULL);
 	if (exec2.flags & __EXEC_HAS_RELOC) {
 		struct drm_i915_gem_exec_object __user *user_exec_list =
 			u64_to_user_ptr(args->buffers_ptr);
@@ -2474,6 +2606,7 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 	const size_t sz = sizeof(struct drm_i915_gem_exec_object2);
 	struct drm_i915_gem_execbuffer2 *args = data;
 	struct drm_i915_gem_exec_object2 *exec2_list;
+	struct drm_syncobj **fences = NULL;
 	int err;
 
 	if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
@@ -2500,7 +2633,15 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 		return -EFAULT;
 	}
 
-	err = i915_gem_do_execbuffer(dev, file, args, exec2_list);
+	if (args->flags & I915_EXEC_FENCE_ARRAY) {
+		fences = get_fence_array(args, file);
+		if (IS_ERR(fences)) {
+			kvfree(exec2_list);
+			return PTR_ERR(fences);
+		}
+	}
+
+	err = i915_gem_do_execbuffer(dev, file, args, exec2_list, fences);
 
 	/*
 	 * Now that we have begun execution of the batchbuffer, we ignore
@@ -2530,6 +2671,7 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 	}
 
 	args->flags &= ~__I915_EXEC_UNKNOWN_FLAGS;
+	put_fence_array(args, fences);
 	kvfree(exec2_list);
 	return err;
 }

include/uapi/drm/i915_drm.h

@@ -435,6 +435,11 @@ typedef struct drm_i915_irq_wait {
  */
 #define I915_PARAM_HAS_EXEC_BATCH_FIRST	 48
 
+/* Query whether DRM_I915_GEM_EXECBUFFER2 supports supplying an array of
+ * drm_i915_gem_exec_fence structures.  See I915_EXEC_FENCE_ARRAY.
+ */
+#define I915_PARAM_HAS_EXEC_FENCE_ARRAY  49
+
 typedef struct drm_i915_getparam {
 	__s32 param;
 	/*
@@ -816,6 +821,17 @@ struct drm_i915_gem_exec_object2 {
 	__u64 rsvd2;
 };
 
+struct drm_i915_gem_exec_fence {
+	/**
+	 * User's handle for a drm_syncobj to wait on or signal.
+	 */
+	__u32 handle;
+
+#define I915_EXEC_FENCE_WAIT            (1<<0)
+#define I915_EXEC_FENCE_SIGNAL          (1<<1)
+	__u32 flags;
+};
+
 struct drm_i915_gem_execbuffer2 {
 	/**
 	 * List of gem_exec_object2 structs
@@ -830,7 +846,11 @@ struct drm_i915_gem_execbuffer2 {
 	__u32 DR1;
 	__u32 DR4;
 	__u32 num_cliprects;
-	/** This is a struct drm_clip_rect *cliprects */
+	/**
+	 * This is a struct drm_clip_rect *cliprects if I915_EXEC_FENCE_ARRAY
+	 * is not set.  If I915_EXEC_FENCE_ARRAY is set, then this is a
+	 * struct drm_i915_gem_exec_fence *fences.
+	 */
 	__u64 cliprects_ptr;
 #define I915_EXEC_RING_MASK              (7<<0)
 #define I915_EXEC_DEFAULT                (0<<0)
@@ -931,7 +951,14 @@ struct drm_i915_gem_execbuffer2 {
  * element).
  */
 #define I915_EXEC_BATCH_FIRST		(1<<18)
-#define __I915_EXEC_UNKNOWN_FLAGS (-(I915_EXEC_BATCH_FIRST<<1))
+
+/* Setting I915_FENCE_ARRAY implies that num_cliprects and cliprects_ptr
+ * define an array of i915_gem_exec_fence structures which specify a set of
+ * dma fences to wait upon or signal.
+ */
+#define I915_EXEC_FENCE_ARRAY   (1<<19)
+
+#define __I915_EXEC_UNKNOWN_FLAGS (-(I915_EXEC_FENCE_ARRAY<<1))
 
 #define I915_EXEC_CONTEXT_ID_MASK	(0xffffffff)
 #define i915_execbuffer2_set_context_id(eb2, context) \