[dpdk-dev] [PATCH v4 4/9] gpudev: support multi-process

[<eagostini@nvidia.com>]

From: Thomas Monjalon <thomas@monjalon.net>

The device data shared between processes are moved in a struct
allocated in a shared memory (a new memzone for all GPUs).
The main struct rte_gpu references the shared memory
via the pointer mpshared.

The API function rte_gpu_attach() is added to attach a device
from the secondary process.
The function rte_gpu_allocate() can be used only by primary process.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
---
 lib/gpudev/gpudev.c        | 127 +++++++++++++++++++++++++++++++------
 lib/gpudev/gpudev_driver.h |  25 ++++++--
 lib/gpudev/version.map     |   1 +
 3 files changed, 127 insertions(+), 26 deletions(-)

diff --git a/lib/gpudev/gpudev.c b/lib/gpudev/gpudev.c
index 74cdd7f20b..f0690cf730 100644
--- a/lib/gpudev/gpudev.c
+++ b/lib/gpudev/gpudev.c
@@ -5,6 +5,7 @@
 #include <rte_eal.h>
 #include <rte_tailq.h>
 #include <rte_string_fns.h>
+#include <rte_memzone.h>
 #include <rte_errno.h>
 #include <rte_log.h>
 
@@ -28,6 +29,12 @@ static int16_t gpu_max;
 /* Number of currently valid devices */
 static int16_t gpu_count;
 
+/* Shared memory between processes. */
+static const char *GPU_MEMZONE = "rte_gpu_shared";
+static struct {
+	__extension__ struct rte_gpu_mpshared gpus[0];
+} *gpu_shared_mem;
+
 /* Event callback object */
 struct rte_gpu_callback {
 	TAILQ_ENTRY(rte_gpu_callback) next;
@@ -75,7 +82,7 @@ bool
 rte_gpu_is_valid(int16_t dev_id)
 {
 	if (dev_id >= 0 && dev_id < gpu_max &&
-		gpus[dev_id].state == RTE_GPU_STATE_INITIALIZED)
+		gpus[dev_id].process_state == RTE_GPU_STATE_INITIALIZED)
 		return true;
 	return false;
 }
@@ -85,7 +92,7 @@ gpu_match_parent(int16_t dev_id, int16_t parent)
 {
 	if (parent == RTE_GPU_ID_ANY)
 		return true;
-	return gpus[dev_id].info.parent == parent;
+	return gpus[dev_id].mpshared->info.parent == parent;
 }
 
 int16_t
@@ -94,7 +101,7 @@ rte_gpu_find_next(int16_t dev_id, int16_t parent)
 	if (dev_id < 0)
 		dev_id = 0;
 	while (dev_id < gpu_max &&
-			(gpus[dev_id].state == RTE_GPU_STATE_UNUSED ||
+			(gpus[dev_id].process_state == RTE_GPU_STATE_UNUSED ||
 			!gpu_match_parent(dev_id, parent)))
 		dev_id++;
 
@@ -109,7 +116,7 @@ gpu_find_free_id(void)
 	int16_t dev_id;
 
 	for (dev_id = 0; dev_id < gpu_max; dev_id++) {
-		if (gpus[dev_id].state == RTE_GPU_STATE_UNUSED)
+		if (gpus[dev_id].process_state == RTE_GPU_STATE_UNUSED)
 			return dev_id;
 	}
 	return RTE_GPU_ID_NONE;
@@ -136,12 +143,35 @@ rte_gpu_get_by_name(const char *name)
 
 	RTE_GPU_FOREACH(dev_id) {
 		dev = &gpus[dev_id];
-		if (strncmp(name, dev->name, RTE_DEV_NAME_MAX_LEN) == 0)
+		if (strncmp(name, dev->mpshared->name, RTE_DEV_NAME_MAX_LEN) == 0)
 			return dev;
 	}
 	return NULL;
 }
 
+static int
+gpu_shared_mem_init(void)
+{
+	const struct rte_memzone *memzone;
+
+	if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
+		memzone = rte_memzone_reserve(GPU_MEMZONE,
+				sizeof(*gpu_shared_mem) +
+				sizeof(*gpu_shared_mem->gpus) * gpu_max,
+				SOCKET_ID_ANY, 0);
+	} else {
+		memzone = rte_memzone_lookup(GPU_MEMZONE);
+	}
+	if (memzone == NULL) {
+		GPU_LOG(ERR, "cannot initialize shared memory");
+		rte_errno = ENOMEM;
+		return -rte_errno;
+	}
+
+	gpu_shared_mem = memzone->addr;
+	return 0;
+}
+
 struct rte_gpu *
 rte_gpu_allocate(const char *name)
 {
@@ -163,6 +193,10 @@ rte_gpu_allocate(const char *name)
 	if (gpus == NULL && rte_gpu_init(RTE_GPU_DEFAULT_MAX) < 0)
 		return NULL;
 
+	/* initialize shared memory before adding first device */
+	if (gpu_shared_mem == NULL && gpu_shared_mem_init() < 0)
+		return NULL;
+
 	if (rte_gpu_get_by_name(name) != NULL) {
 		GPU_LOG(ERR, "device with name %s already exists", name);
 		rte_errno = EEXIST;
@@ -178,16 +212,20 @@ rte_gpu_allocate(const char *name)
 	dev = &gpus[dev_id];
 	memset(dev, 0, sizeof(*dev));
 
-	if (rte_strscpy(dev->name, name, RTE_DEV_NAME_MAX_LEN) < 0) {
+	dev->mpshared = &gpu_shared_mem->gpus[dev_id];
+	memset(dev->mpshared, 0, sizeof(*dev->mpshared));
+
+	if (rte_strscpy(dev->mpshared->name, name, RTE_DEV_NAME_MAX_LEN) < 0) {
 		GPU_LOG(ERR, "device name too long: %s", name);
 		rte_errno = ENAMETOOLONG;
 		return NULL;
 	}
-	dev->info.name = dev->name;
-	dev->info.dev_id = dev_id;
-	dev->info.numa_node = -1;
-	dev->info.parent = RTE_GPU_ID_NONE;
+	dev->mpshared->info.name = dev->mpshared->name;
+	dev->mpshared->info.dev_id = dev_id;
+	dev->mpshared->info.numa_node = -1;
+	dev->mpshared->info.parent = RTE_GPU_ID_NONE;
 	TAILQ_INIT(&dev->callbacks);
+	__atomic_fetch_add(&dev->mpshared->process_refcnt, 1, __ATOMIC_RELAXED);
 
 	gpu_count++;
 	GPU_LOG(DEBUG, "new device %s (id %d) of total %d",
@@ -195,6 +233,55 @@ rte_gpu_allocate(const char *name)
 	return dev;
 }
 
+struct rte_gpu *
+rte_gpu_attach(const char *name)
+{
+	int16_t dev_id;
+	struct rte_gpu *dev;
+	struct rte_gpu_mpshared *shared_dev;
+
+	if (rte_eal_process_type() != RTE_PROC_SECONDARY) {
+		GPU_LOG(ERR, "only secondary process can attach device");
+		rte_errno = EPERM;
+		return NULL;
+	}
+	if (name == NULL) {
+		GPU_LOG(ERR, "attach device without a name");
+		rte_errno = EINVAL;
+		return NULL;
+	}
+
+	/* implicit initialization of library before adding first device */
+	if (gpus == NULL && rte_gpu_init(RTE_GPU_DEFAULT_MAX) < 0)
+		return NULL;
+
+	/* initialize shared memory before adding first device */
+	if (gpu_shared_mem == NULL && gpu_shared_mem_init() < 0)
+		return NULL;
+
+	for (dev_id = 0; dev_id < gpu_max; dev_id++) {
+		shared_dev = &gpu_shared_mem->gpus[dev_id];
+		if (strncmp(name, shared_dev->name, RTE_DEV_NAME_MAX_LEN) == 0)
+			break;
+	}
+	if (dev_id >= gpu_max) {
+		GPU_LOG(ERR, "device with name %s not found", name);
+		rte_errno = ENOENT;
+		return NULL;
+	}
+	dev = &gpus[dev_id];
+	memset(dev, 0, sizeof(*dev));
+
+	TAILQ_INIT(&dev->callbacks);
+	dev->mpshared = shared_dev;
+	__atomic_fetch_add(&dev->mpshared->process_refcnt, 1, __ATOMIC_RELAXED);
+
+	gpu_count++;
+	GPU_LOG(DEBUG, "attached device %s (id %d) of total %d",
+			name, dev_id, gpu_count);
+	return dev;
+}
+
 int16_t
 rte_gpu_add_child(const char *name, int16_t parent, uint64_t child_context)
 {
@@ -210,11 +297,11 @@ rte_gpu_add_child(const char *name, int16_t parent, uint64_t child_context)
 	if (dev == NULL)
 		return -rte_errno;
 
-	dev->info.parent = parent;
-	dev->info.context = child_context;
+	dev->mpshared->info.parent = parent;
+	dev->mpshared->info.context = child_context;
 
 	rte_gpu_complete_new(dev);
-	return dev->info.dev_id;
+	return dev->mpshared->info.dev_id;
 }
 
 void
@@ -223,8 +310,7 @@ rte_gpu_complete_new(struct rte_gpu *dev)
 	if (dev == NULL)
 		return;
 
-	dev->state = RTE_GPU_STATE_INITIALIZED;
-	dev->state = RTE_GPU_STATE_INITIALIZED;
+	dev->process_state = RTE_GPU_STATE_INITIALIZED;
 	rte_gpu_notify(dev, RTE_GPU_EVENT_NEW);
 }
 
@@ -237,7 +323,7 @@ rte_gpu_release(struct rte_gpu *dev)
 		rte_errno = ENODEV;
 		return -rte_errno;
 	}
-	dev_id = dev->info.dev_id;
+	dev_id = dev->mpshared->info.dev_id;
 	RTE_GPU_FOREACH_CHILD(child, dev_id) {
 		GPU_LOG(ERR, "cannot release device %d with child %d",
 				dev_id, child);
@@ -246,11 +332,12 @@ rte_gpu_release(struct rte_gpu *dev)
 	}
 
 	GPU_LOG(DEBUG, "free device %s (id %d)",
-			dev->info.name, dev->info.dev_id);
+			dev->mpshared->info.name, dev->mpshared->info.dev_id);
 	rte_gpu_notify(dev, RTE_GPU_EVENT_DEL);
 
 	gpu_free_callbacks(dev);
-	dev->state = RTE_GPU_STATE_UNUSED;
+	dev->process_state = RTE_GPU_STATE_UNUSED;
+	__atomic_fetch_sub(&dev->mpshared->process_refcnt, 1, __ATOMIC_RELAXED);
 	gpu_count--;
 
 	return 0;
@@ -403,7 +490,7 @@ rte_gpu_notify(struct rte_gpu *dev, enum rte_gpu_event event)
 	int16_t dev_id;
 	struct rte_gpu_callback *callback;
 
-	dev_id = dev->info.dev_id;
+	dev_id = dev->mpshared->info.dev_id;
 	rte_rwlock_read_lock(&gpu_callback_lock);
 	TAILQ_FOREACH(callback, &dev->callbacks, next) {
 		if (callback->event != event || callback->function == NULL)
@@ -431,7 +518,7 @@ rte_gpu_info_get(int16_t dev_id, struct rte_gpu_info *info)
 	}
 
 	if (dev->ops.dev_info_get == NULL) {
-		*info = dev->info;
+		*info = dev->mpshared->info;
 		return 0;
 	}
 	return GPU_DRV_RET(dev->ops.dev_info_get(dev, info));
diff --git a/lib/gpudev/gpudev_driver.h b/lib/gpudev/gpudev_driver.h
index 4d0077161c..9459c7e30f 100644
--- a/lib/gpudev/gpudev_driver.h
+++ b/lib/gpudev/gpudev_driver.h
@@ -35,19 +35,28 @@ struct rte_gpu_ops {
 	rte_gpu_close_t *dev_close;
 };
 
-struct rte_gpu {
-	/* Backing device. */
-	struct rte_device *device;
+struct rte_gpu_mpshared {
 	/* Unique identifier name. */
 	char name[RTE_DEV_NAME_MAX_LEN]; /* Updated by this library. */
+	/* Driver-specific private data shared in multi-process. */
+	void *dev_private;
 	/* Device info structure. */
 	struct rte_gpu_info info;
+	/* Counter of processes using the device. */
+	uint16_t process_refcnt; /* Updated by this library. */
+};
+
+struct rte_gpu {
+	/* Backing device. */
+	struct rte_device *device;
+	/* Data shared between processes. */
+	struct rte_gpu_mpshared *mpshared;
 	/* Driver functions. */
 	struct rte_gpu_ops ops;
 	/* Event callback list. */
 	TAILQ_HEAD(rte_gpu_callback_list, rte_gpu_callback) callbacks;
 	/* Current state (used or not) in the running process. */
-	enum rte_gpu_state state; /* Updated by this library. */
+	enum rte_gpu_state process_state; /* Updated by this library. */
 	/* Driver-specific private data for the running process. */
 	void *process_private;
 } __rte_cache_aligned;
@@ -55,15 +64,19 @@ struct rte_gpu {
 __rte_internal
 struct rte_gpu *rte_gpu_get_by_name(const char *name);
 
-/* First step of initialization */
+/* First step of initialization in primary process. */
 __rte_internal
 struct rte_gpu *rte_gpu_allocate(const char *name);
 
+/* First step of initialization in secondary process. */
+__rte_internal
+struct rte_gpu *rte_gpu_attach(const char *name);
+
 /* Last step of initialization. */
 __rte_internal
 void rte_gpu_complete_new(struct rte_gpu *dev);
 
-/* Last step of removal. */
+/* Last step of removal (primary or secondary process). */
 __rte_internal
 int rte_gpu_release(struct rte_gpu *dev);
 
diff --git a/lib/gpudev/version.map b/lib/gpudev/version.map
index 4a934ed933..58dc632393 100644
--- a/lib/gpudev/version.map
+++ b/lib/gpudev/version.map
@@ -17,6 +17,7 @@ INTERNAL {
 	global:
 
 	rte_gpu_allocate;
+	rte_gpu_attach;
 	rte_gpu_complete_new;
 	rte_gpu_get_by_name;
 	rte_gpu_notify;
-- 
2.17.1