Re: [PATCH 4/4] amdgpu: use sync file for shared semaphores

Christian König <deathsimple@xxxxxxxxxxx> · Wed, 15 Mar 2017 10:43:01 +0100

Am 15.03.2017 um 10:01 schrieb Daniel Vetter:
On Tue, Mar 14, 2017 at 10:50:54AM +1000, Dave Airlie wrote:
From: Dave Airlie <airlied@xxxxxxxxxx>

This creates a new interface for amdgpu with ioctls to
create/destroy/import and export shared semaphores using
sem object backed by the sync_file code. The semaphores
are not installed as fd (except for export), but rather
like other driver internal objects in an idr. The idr
holds the initial reference on the sync file.

The command submission interface is enhanced with two new
chunks, one for semaphore waiting, one for semaphore signalling
and just takes a list of handles for each.

This is based on work originally done by David Zhou at AMD,
with input from Christian Konig on what things should look like.

NOTE: this interface addition needs a version bump to expose
it to userspace.

Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Another uapi corner case: Since you allow semaphores to be created before
they have a first fence attached, that essentially creates future fences.
I.e. sync_file fd with no fence yet attached. We want that anyway, but
maybe not together with semaphores (since there's some more implications).

I think it'd be good to attach a dummy fence which already starts out as
signalled to sync_file->fence for semaphores. That way userspace can't go
evil, create a semaphore, then pass it to a driver which then promptly
oopses or worse because it assumes then when it has a sync_file, it also
has a fence. And the dummy fence could be globally shared, so not really
overhead.

Sounds fishy to me, what happens in case of a race condition and the 
receiver sometimes waits on the dummy and sometimes on the real fence?

I would rather teach the users of sync_file to return a proper error 
code when you want to wait on a sync_file which doesn't have a fence yet.

Christian.

-Daniel

---
  drivers/gpu/drm/amd/amdgpu/Makefile     |   2 +-
  drivers/gpu/drm/amd/amdgpu/amdgpu.h     |  12 ++
  drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c  |  70 ++++++++++-
  drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c |   8 ++
  drivers/gpu/drm/amd/amdgpu/amdgpu_sem.c | 204 ++++++++++++++++++++++++++++++++
  include/uapi/drm/amdgpu_drm.h           |  28 +++++
  6 files changed, 322 insertions(+), 2 deletions(-)
  create mode 100644 drivers/gpu/drm/amd/amdgpu/amdgpu_sem.c

diff --git a/drivers/gpu/drm/amd/amdgpu/Makefile b/drivers/gpu/drm/amd/amdgpu/Makefile
index 2814aad..404bcba 100644
--- a/drivers/gpu/drm/amd/amdgpu/Makefile
+++ b/drivers/gpu/drm/amd/amdgpu/Makefile
@@ -24,7 +24,7 @@ amdgpu-y += amdgpu_device.o amdgpu_kms.o \
  	atombios_encoders.o amdgpu_sa.o atombios_i2c.o \
  	amdgpu_prime.o amdgpu_vm.o amdgpu_ib.o amdgpu_pll.o \
  	amdgpu_ucode.o amdgpu_bo_list.o amdgpu_ctx.o amdgpu_sync.o \
-	amdgpu_gtt_mgr.o amdgpu_vram_mgr.o amdgpu_virt.o
+	amdgpu_gtt_mgr.o amdgpu_vram_mgr.o amdgpu_virt.o amdgpu_sem.o
  
  # add asic specific block
  amdgpu-$(CONFIG_DRM_AMDGPU_CIK)+= cik.o cik_ih.o kv_smc.o kv_dpm.o \
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index c1b9135..4ed8811 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -702,6 +702,8 @@ struct amdgpu_fpriv {
  	struct mutex		bo_list_lock;
  	struct idr		bo_list_handles;
  	struct amdgpu_ctx_mgr	ctx_mgr;
+	spinlock_t		sem_handles_lock;
+	struct idr		sem_handles;
  };
  
  /*
@@ -1814,5 +1816,15 @@ amdgpu_cs_find_mapping(struct amdgpu_cs_parser *parser,
  		       uint64_t addr, struct amdgpu_bo **bo);
  int amdgpu_cs_sysvm_access_required(struct amdgpu_cs_parser *parser);
  
+int amdgpu_sem_ioctl(struct drm_device *dev, void *data,
+		     struct drm_file *filp);
+void amdgpu_sem_destroy(struct amdgpu_fpriv *fpriv, u32 handle);
+int amdgpu_sem_lookup_and_signal(struct amdgpu_fpriv *fpriv,
+				 uint32_t handle,
+				 struct dma_fence *fence);
+int amdgpu_sem_lookup_and_sync(struct amdgpu_device *adev,
+			       struct amdgpu_fpriv *fpriv,
+			       struct amdgpu_sync *sync,
+			       uint32_t handle);
  #include "amdgpu_object.h"
  #endif
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 4671432..80fc94b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -217,6 +217,8 @@ int amdgpu_cs_parser_init(struct amdgpu_cs_parser *p, void *data)
  			break;
  
  		case AMDGPU_CHUNK_ID_DEPENDENCIES:
+		case AMDGPU_CHUNK_ID_SEM_WAIT:
+		case AMDGPU_CHUNK_ID_SEM_SIGNAL:
  			break;
  
  		default:
@@ -1009,6 +1011,28 @@ static int amdgpu_process_fence_dep(struct amdgpu_device *adev,
  	return 0;
  }
  
+static int amdgpu_process_sem_wait_dep(struct amdgpu_device *adev,
+				       struct amdgpu_cs_parser *p,
+				       struct amdgpu_cs_chunk *chunk)
+{
+	struct amdgpu_fpriv *fpriv = p->filp->driver_priv;
+	unsigned num_deps;
+	int i, r;
+	struct drm_amdgpu_cs_chunk_sem *deps;
+
+	deps = (struct drm_amdgpu_cs_chunk_sem *)chunk->kdata;
+	num_deps = chunk->length_dw * 4 /
+		sizeof(struct drm_amdgpu_cs_chunk_sem);
+
+	for (i = 0; i < num_deps; ++i) {
+		r = amdgpu_sem_lookup_and_sync(adev, fpriv, &p->job->sync,
+					       deps[i].handle);
+		if (r)
+			return r;
+	}
+	return 0;
+}
+
  static int amdgpu_cs_dependencies(struct amdgpu_device *adev,
  				  struct amdgpu_cs_parser *p)
  {
@@ -1023,12 +1047,56 @@ static int amdgpu_cs_dependencies(struct amdgpu_device *adev,
  			r = amdgpu_process_fence_dep(adev, p, chunk);
  			if (r)
  				return r;
+		} else if (chunk->chunk_id == AMDGPU_CHUNK_ID_SEM_WAIT) {
+			r = amdgpu_process_sem_wait_dep(adev, p, chunk);
+			if (r)
+				return r;
  		}
  	}
  
  	return 0;
  }
  
+static int amdgpu_process_sem_signal_dep(struct amdgpu_cs_parser *p,
+					 struct amdgpu_cs_chunk *chunk,
+					 struct dma_fence *fence)
+{
+	struct amdgpu_fpriv *fpriv = p->filp->driver_priv;
+	unsigned num_deps;
+	int i, r;
+	struct drm_amdgpu_cs_chunk_sem *deps;
+
+	deps = (struct drm_amdgpu_cs_chunk_sem *)chunk->kdata;
+	num_deps = chunk->length_dw * 4 /
+		sizeof(struct drm_amdgpu_cs_chunk_sem);
+
+	for (i = 0; i < num_deps; ++i) {
+		r = amdgpu_sem_lookup_and_signal(fpriv, deps[i].handle,
+						 fence);
+		if (r)
+			return r;
+	}
+	return 0;
+}
+
+static int amdgpu_cs_post_dependencies(struct amdgpu_cs_parser *p)
+{
+	int i, r;
+
+	for (i = 0; i < p->nchunks; ++i) {
+		struct amdgpu_cs_chunk *chunk;
+
+		chunk = &p->chunks[i];
+
+		if (chunk->chunk_id == AMDGPU_CHUNK_ID_SEM_SIGNAL) {
+			r = amdgpu_process_sem_signal_dep(p, chunk, p->fence);
+			if (r)
+				return r;
+		}
+	}
+	return 0;
+}
+
  static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
  			    union drm_amdgpu_cs *cs)
  {
@@ -1056,7 +1124,7 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
  	trace_amdgpu_cs_ioctl(job);
  	amd_sched_entity_push_job(&job->base);
  
-	return 0;
+	return amdgpu_cs_post_dependencies(p);
  }
  
  int amdgpu_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
index 61d94c7..013aed1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
@@ -664,6 +664,8 @@ int amdgpu_driver_open_kms(struct drm_device *dev, struct drm_file *file_priv)
  	mutex_init(&fpriv->bo_list_lock);
  	idr_init(&fpriv->bo_list_handles);
  
+	spin_lock_init(&fpriv->sem_handles_lock);
+	idr_init(&fpriv->sem_handles);
  	amdgpu_ctx_mgr_init(&fpriv->ctx_mgr);
  
  	file_priv->driver_priv = fpriv;
@@ -689,6 +691,7 @@ void amdgpu_driver_postclose_kms(struct drm_device *dev,
  	struct amdgpu_device *adev = dev->dev_private;
  	struct amdgpu_fpriv *fpriv = file_priv->driver_priv;
  	struct amdgpu_bo_list *list;
+	struct amdgpu_sem *sem;
  	int handle;
  
  	if (!fpriv)
@@ -715,6 +718,10 @@ void amdgpu_driver_postclose_kms(struct drm_device *dev,
  	idr_destroy(&fpriv->bo_list_handles);
  	mutex_destroy(&fpriv->bo_list_lock);
  
+	idr_for_each_entry(&fpriv->sem_handles, sem, handle)
+		amdgpu_sem_destroy(fpriv, handle);
+	idr_destroy(&fpriv->sem_handles);
+
  	kfree(fpriv);
  	file_priv->driver_priv = NULL;
  
@@ -896,6 +903,7 @@ const struct drm_ioctl_desc amdgpu_ioctls_kms[] = {
  	DRM_IOCTL_DEF_DRV(AMDGPU_GEM_VA, amdgpu_gem_va_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
  	DRM_IOCTL_DEF_DRV(AMDGPU_GEM_OP, amdgpu_gem_op_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
  	DRM_IOCTL_DEF_DRV(AMDGPU_GEM_USERPTR, amdgpu_gem_userptr_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF_DRV(AMDGPU_SEM, amdgpu_sem_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
  };
  const int amdgpu_max_kms_ioctl = ARRAY_SIZE(amdgpu_ioctls_kms);
  
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sem.c
new file mode 100644
index 0000000..066520a
--- /dev/null
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sem.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright 2016 Advanced Micro Devices, Inc.
+ *
+ * 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
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice 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 MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
+ *
+ * Authors:
+ *    Chunming Zhou <david1.zhou@xxxxxxx>
+ */
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/poll.h>
+#include <linux/seq_file.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/anon_inodes.h>
+#include <linux/sync_file.h>
+#include "amdgpu.h"
+#include <drm/drmP.h>
+
+static inline struct sync_file *amdgpu_sync_file_lookup(struct amdgpu_fpriv *fpriv, u32 handle)
+{
+	struct sync_file *sync_file;
+
+	spin_lock(&fpriv->sem_handles_lock);
+
+	/* Check if we currently have a reference on the object */
+	sync_file = idr_find(&fpriv->sem_handles, handle);
+
+	spin_unlock(&fpriv->sem_handles_lock);
+
+	return sync_file;
+}
+
+static int amdgpu_sem_create(struct amdgpu_fpriv *fpriv, u32 *handle)
+{
+	struct sync_file *sync_file = sync_file_alloc();
+	int ret;
+
+	if (!sync_file)
+		return -ENOMEM;
+
+	snprintf(sync_file->name, sizeof(sync_file->name), "sync_sem");
+
+	/* we get a file reference and we use that in the idr. */
+	idr_preload(GFP_KERNEL);
+	spin_lock(&fpriv->sem_handles_lock);
+
+	ret = idr_alloc(&fpriv->sem_handles, sync_file, 1, 0, GFP_NOWAIT);
+
+	spin_unlock(&fpriv->sem_handles_lock);
+	idr_preload_end();
+
+	if (ret < 0)
+		return ret;
+
+	*handle = ret;
+	return 0;
+}
+
+void amdgpu_sem_destroy(struct amdgpu_fpriv *fpriv, u32 handle)
+{
+	struct sync_file *sync_file = amdgpu_sync_file_lookup(fpriv, handle);
+	if (!sync_file)
+		return;
+
+	spin_lock(&fpriv->sem_handles_lock);
+	idr_remove(&fpriv->sem_handles, handle);
+	spin_unlock(&fpriv->sem_handles_lock);
+
+	fput(sync_file->file);
+}
+
+
+int amdgpu_sem_lookup_and_signal(struct amdgpu_fpriv *fpriv,
+				 uint32_t handle,
+				 struct dma_fence *fence)
+{
+	struct sync_file *sync_file;
+	struct dma_fence *old_fence;
+	sync_file = amdgpu_sync_file_lookup(fpriv, handle);
+	if (!sync_file)
+		return -EINVAL;
+
+	old_fence = sync_file_replace_fence(sync_file, fence);
+	dma_fence_put(old_fence);
+	return 0;
+}
+
+static int amdgpu_sem_import(struct amdgpu_fpriv *fpriv,
+				       int fd, u32 *handle)
+{
+	struct sync_file *sync_file = sync_file_fdget(fd);
+	int ret;
+
+	if (!sync_file)
+		return -EINVAL;
+
+	idr_preload(GFP_KERNEL);
+	spin_lock(&fpriv->sem_handles_lock);
+
+	ret = idr_alloc(&fpriv->sem_handles, sync_file, 1, 0, GFP_NOWAIT);
+
+	spin_unlock(&fpriv->sem_handles_lock);
+	idr_preload_end();
+
+	fput(sync_file->file);
+	if (ret < 0)
+		goto err_out;
+
+	*handle = ret;
+	return 0;
+err_out:
+	return ret;
+
+}
+
+static int amdgpu_sem_export(struct amdgpu_fpriv *fpriv,
+			     u32 handle, int *fd)
+{
+	struct sync_file *sync_file;
+	int ret;
+
+	sync_file = amdgpu_sync_file_lookup(fpriv, handle);
+	if (!sync_file)
+		return -EINVAL;
+
+	ret = get_unused_fd_flags(O_CLOEXEC);
+	if (ret < 0)
+		goto err_put_file;
+
+	fd_install(ret, sync_file->file);
+
+	*fd = ret;
+	return 0;
+err_put_file:
+	return ret;
+}
+
+int amdgpu_sem_lookup_and_sync(struct amdgpu_device *adev,
+			       struct amdgpu_fpriv *fpriv,
+			       struct amdgpu_sync *sync,
+			       uint32_t handle)
+{
+	int r;
+	struct sync_file *sync_file;
+	struct dma_fence *fence;
+
+	sync_file = amdgpu_sync_file_lookup(fpriv, handle);
+	if (!sync_file)
+		return -EINVAL;
+
+	fence = sync_file_replace_fence(sync_file, NULL);
+	r = amdgpu_sync_fence(adev, sync, fence);
+	dma_fence_put(fence);
+
+	return r;
+}
+
+int amdgpu_sem_ioctl(struct drm_device *dev, void *data,
+		     struct drm_file *filp)
+{
+	union drm_amdgpu_sem *args = data;
+	struct amdgpu_fpriv *fpriv = filp->driver_priv;
+	int r = 0;
+
+	switch (args->in.op) {
+	case AMDGPU_SEM_OP_CREATE_SEM:
+		r = amdgpu_sem_create(fpriv, &args->out.handle);
+		break;
+	case AMDGPU_SEM_OP_IMPORT_SEM:
+		r = amdgpu_sem_import(fpriv, args->in.handle, &args->out.handle);
+		break;
+	case AMDGPU_SEM_OP_EXPORT_SEM:
+		r = amdgpu_sem_export(fpriv, args->in.handle, &args->out.fd);
+		break;
+	case AMDGPU_SEM_OP_DESTROY_SEM:
+		amdgpu_sem_destroy(fpriv, args->in.handle);
+		break;
+	default:
+		r = -EINVAL;
+		break;
+	}
+
+	return r;
+}
diff --git a/include/uapi/drm/amdgpu_drm.h b/include/uapi/drm/amdgpu_drm.h
index 5797283..646b103 100644
--- a/include/uapi/drm/amdgpu_drm.h
+++ b/include/uapi/drm/amdgpu_drm.h
@@ -51,6 +51,7 @@ extern "C" {
  #define DRM_AMDGPU_GEM_OP		0x10
  #define DRM_AMDGPU_GEM_USERPTR		0x11
  #define DRM_AMDGPU_WAIT_FENCES		0x12
+#define DRM_AMDGPU_SEM                  0x13
  
  #define DRM_IOCTL_AMDGPU_GEM_CREATE	DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_GEM_CREATE, union drm_amdgpu_gem_create)
  #define DRM_IOCTL_AMDGPU_GEM_MMAP	DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_GEM_MMAP, union drm_amdgpu_gem_mmap)
@@ -65,6 +66,7 @@ extern "C" {
  #define DRM_IOCTL_AMDGPU_GEM_OP		DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_GEM_OP, struct drm_amdgpu_gem_op)
  #define DRM_IOCTL_AMDGPU_GEM_USERPTR	DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_GEM_USERPTR, struct drm_amdgpu_gem_userptr)
  #define DRM_IOCTL_AMDGPU_WAIT_FENCES	DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_WAIT_FENCES, union drm_amdgpu_wait_fences)
+#define DRM_IOCTL_AMDGPU_SEM		DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_SEM, union drm_amdgpu_sem)
  
  #define AMDGPU_GEM_DOMAIN_CPU		0x1
  #define AMDGPU_GEM_DOMAIN_GTT		0x2
@@ -335,6 +337,26 @@ union drm_amdgpu_wait_fences {
  	struct drm_amdgpu_wait_fences_out out;
  };
  
+#define AMDGPU_SEM_OP_CREATE_SEM 0
+#define AMDGPU_SEM_OP_IMPORT_SEM 1
+#define AMDGPU_SEM_OP_EXPORT_SEM 2
+#define AMDGPU_SEM_OP_DESTROY_SEM 3
+
+struct drm_amdgpu_sem_in {
+	__u32 op;
+	__u32 handle;
+};
+
+struct drm_amdgpu_sem_out {
+	__u32 fd;
+	__u32 handle;
+};
+
+union drm_amdgpu_sem {
+	struct drm_amdgpu_sem_in in;
+	struct drm_amdgpu_sem_out out;
+};
+
  #define AMDGPU_GEM_OP_GET_GEM_CREATE_INFO	0
  #define AMDGPU_GEM_OP_SET_PLACEMENT		1
  
@@ -390,6 +412,8 @@ struct drm_amdgpu_gem_va {
  #define AMDGPU_CHUNK_ID_IB		0x01
  #define AMDGPU_CHUNK_ID_FENCE		0x02
  #define AMDGPU_CHUNK_ID_DEPENDENCIES	0x03
+#define AMDGPU_CHUNK_ID_SEM_WAIT        0x04
+#define AMDGPU_CHUNK_ID_SEM_SIGNAL      0x05
  
  struct drm_amdgpu_cs_chunk {
  	__u32		chunk_id;
@@ -454,6 +478,10 @@ struct drm_amdgpu_cs_chunk_fence {
  	__u32 offset;
  };
  
+struct drm_amdgpu_cs_chunk_sem {
+	__u32 handle;
+};
+
  struct drm_amdgpu_cs_chunk_data {
  	union {
  		struct drm_amdgpu_cs_chunk_ib		ib_data;
--
2.7.4

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