[dpdk-dev] [PATCH v2 09/14] vhost: use linked-list for vDPA devices

[Maxime Coquelin <maxime.coquelin@redhat.com>]

There is no more notion of device ID outside of vdpa.c.
We can now move from array to linked-list model for keeping
track of the vDPA devices.

There is no point in using array here, as all vDPA API are
used from the control path, so no performance concerns.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/rte_vdpa.h |   1 +
 lib/librte_vhost/vdpa.c     | 134 +++++++++++++++++++-----------------
 2 files changed, 70 insertions(+), 65 deletions(-)

diff --git a/lib/librte_vhost/rte_vdpa.h b/lib/librte_vhost/rte_vdpa.h
index da8ee33ab1..dbdc273702 100644
--- a/lib/librte_vhost/rte_vdpa.h
+++ b/lib/librte_vhost/rte_vdpa.h
@@ -105,6 +105,7 @@ struct rte_vdpa_dev_ops {
  * vdpa device structure includes device address and device operations.
  */
 struct rte_vdpa_device {
+	TAILQ_ENTRY(rte_vdpa_device) next;
 	/** Generic device information */
 	struct rte_device *device;
 	/** vdpa device operations */
diff --git a/lib/librte_vhost/vdpa.c b/lib/librte_vhost/vdpa.c
index d7965b8854..dc2a138009 100644
--- a/lib/librte_vhost/vdpa.c
+++ b/lib/librte_vhost/vdpa.c
@@ -9,35 +9,54 @@
  */
 
 #include <stdbool.h>
+#include <sys/queue.h>
 
 #include <rte_class.h>
 #include <rte_malloc.h>
+#include <rte_spinlock.h>
+#include <rte_tailq.h>
+
 #include "rte_vdpa.h"
 #include "vhost.h"
 
-static struct rte_vdpa_device vdpa_devices[MAX_VHOST_DEVICE];
+/** Double linked list of vDPA devices. */
+TAILQ_HEAD(vdpa_device_list, rte_vdpa_device);
+
+static struct vdpa_device_list vdpa_device_list =
+		TAILQ_HEAD_INITIALIZER(vdpa_device_list);
+static rte_spinlock_t vdpa_device_list_lock = RTE_SPINLOCK_INITIALIZER;
 static uint32_t vdpa_device_num;
 
 
-struct rte_vdpa_device *
-rte_vdpa_find_device_by_name(const char *name)
+/* Unsafe, needs to be called with vdpa_device_list_lock held */
+static struct rte_vdpa_device *
+__vdpa_find_device_by_name(const char *name)
 {
-	struct rte_vdpa_device *dev;
-	int i;
+	struct rte_vdpa_device *dev, *ret = NULL;
 
 	if (name == NULL)
 		return NULL;
 
-	for (i = 0; i < MAX_VHOST_DEVICE; ++i) {
-		dev = &vdpa_devices[i];
-		if (dev->ops == NULL)
-			continue;
-
-		if (strcmp(dev->device->name, name) == 0)
-			return dev;
+	TAILQ_FOREACH(dev, &vdpa_device_list, next) {
+		if (strcmp(dev->device->name, name) == 0) {
+			ret = dev;
+			break;
+		}
 	}
 
-	return NULL;
+	return ret;
+}
+
+struct rte_vdpa_device *
+rte_vdpa_find_device_by_name(const char *name)
+{
+	struct rte_vdpa_device *dev;
+
+	rte_spinlock_lock(&vdpa_device_list_lock);
+	dev = __vdpa_find_device_by_name(name);
+	rte_spinlock_unlock(&vdpa_device_list_lock);
+
+	return dev;
 }
 
 struct rte_device *
@@ -54,52 +73,52 @@ rte_vdpa_register_device(struct rte_device *rte_dev,
 		struct rte_vdpa_dev_ops *ops)
 {
 	struct rte_vdpa_device *dev;
-	int i;
 
-	if (vdpa_device_num >= MAX_VHOST_DEVICE || ops == NULL)
+	if (ops == NULL)
 		return NULL;
 
-	for (i = 0; i < MAX_VHOST_DEVICE; i++) {
-		dev = &vdpa_devices[i];
-		if (dev->ops == NULL)
-			continue;
-
-		if (dev->device == rte_dev)
-			return NULL;
-	}
-
-	for (i = 0; i < MAX_VHOST_DEVICE; i++) {
-		if (vdpa_devices[i].ops == NULL)
-			break;
+	rte_spinlock_lock(&vdpa_device_list_lock);
+	/* Check the device hasn't been register already */
+	dev = __vdpa_find_device_by_name(rte_dev->name);
+	if (dev) {
+		dev = NULL;
+		goto out_unlock;
 	}
 
-	if (i == MAX_VHOST_DEVICE)
-		return NULL;
+	dev = rte_zmalloc(NULL, sizeof(*dev), 0);
+	if (!dev)
+		goto out_unlock;
 
-	dev = &vdpa_devices[i];
 	dev->device = rte_dev;
 	dev->ops = ops;
+	TAILQ_INSERT_TAIL(&vdpa_device_list, dev, next);
 	vdpa_device_num++;
+out_unlock:
+	rte_spinlock_unlock(&vdpa_device_list_lock);
 
 	return dev;
 }
 
 int
-rte_vdpa_unregister_device(struct rte_vdpa_device *vdev)
+rte_vdpa_unregister_device(struct rte_vdpa_device *dev)
 {
-	int i;
+	struct rte_vdpa_device *cur_dev, *tmp_dev;
+	int ret = -1;
 
-	for (i = 0; i < MAX_VHOST_DEVICE; i++) {
-		if (vdev != &vdpa_devices[i])
+	rte_spinlock_lock(&vdpa_device_list_lock);
+	TAILQ_FOREACH_SAFE(cur_dev, &vdpa_device_list, next, tmp_dev) {
+		if (dev != cur_dev)
 			continue;
 
-		memset(vdev, 0, sizeof(struct rte_vdpa_device));
+		TAILQ_REMOVE(&vdpa_device_list, dev, next);
+		rte_free(dev);
 		vdpa_device_num--;
-
-		return 0;
+		ret = 0;
+		break;
 	}
+	rte_spinlock_lock(&vdpa_device_list_lock);
 
-	return -1;
+	return ret;
 }
 
 int
@@ -246,19 +265,6 @@ rte_vdpa_reset_stats(struct rte_vdpa_device *dev, uint16_t qid)
 	return dev->ops->reset_stats(dev, qid);
 }
 
-static uint16_t
-vdpa_dev_to_id(const struct rte_vdpa_device *dev)
-{
-	if (dev == NULL)
-		return MAX_VHOST_DEVICE;
-
-	if (dev < &vdpa_devices[0] ||
-			dev >= &vdpa_devices[MAX_VHOST_DEVICE])
-		return MAX_VHOST_DEVICE;
-
-	return (uint16_t)(dev - vdpa_devices);
-}
-
 static int
 vdpa_dev_match(struct rte_vdpa_device *dev,
 	      const struct rte_device *rte_dev)
@@ -278,24 +284,22 @@ vdpa_find_device(const struct rte_vdpa_device *start, rte_vdpa_cmp_t cmp,
 		struct rte_device *rte_dev)
 {
 	struct rte_vdpa_device *dev;
-	uint16_t idx;
 
-	if (start != NULL)
-		idx = vdpa_dev_to_id(start) + 1;
+	rte_spinlock_lock(&vdpa_device_list_lock);
+	if (start == NULL)
+		dev = TAILQ_FIRST(&vdpa_device_list);
 	else
-		idx = 0;
-	for (; idx < MAX_VHOST_DEVICE; idx++) {
-		dev = &vdpa_devices[idx];
-		/*
-		 * ToDo: Certainly better to introduce a state field,
-		 * but rely on ops being set for now.
-		 */
-		if (dev->ops == NULL)
-			continue;
+		dev = TAILQ_NEXT(start, next);
+
+	while (dev != NULL) {
 		if (cmp(dev, rte_dev) == 0)
-			return dev;
+			break;
+
+		dev = TAILQ_NEXT(dev, next);
 	}
-	return NULL;
+	rte_spinlock_unlock(&vdpa_device_list_lock);
+
+	return dev;
 }
 
 static void *
-- 
2.26.2