[dpdk-dev] [PATCH 1/2] eal/mempool: introduce check for external mempool availability

[Hemant Agrawal]

External offloaded mempool may not be available always. This check enables
run time verification of the presence of external mempool before the
mempool ops are installed. 

An application built with a specific external mempool may work fine
on host. But, may not work on VM, specificaly if non-hw specific interfaces
are used e.g. virtio-net.

This is required to make sure that same application can work in all
environment for a given hw platform.

The solution proposed here is that rte_mempool_set_ops_byname should return
specific error in case the current execution environment is not supporting
the given mempool. Thereby allowing it to fallback on software mempool
implementation e.g. "ring_mp_mc"

This patch introduces new optional "pool_verify" as mempool ops function
to check if external mempool instance is available or not.

Signed-off-by: Hemant Agrawal <hemant.agrawal at nxp.com>
---
 lib/librte_mempool/rte_mempool.h       | 21 +++++++++++++++++++++
 lib/librte_mempool/rte_mempool_ops.c   | 18 ++++++++++++++++++
 lib/librte_mempool/rte_mempool_ring.c  |  4 ++++
 lib/librte_mempool/rte_mempool_stack.c |  3 ++-
 4 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/lib/librte_mempool/rte_mempool.h b/lib/librte_mempool/rte_mempool.h
index 059ad9e..67e12d1 100644
--- a/lib/librte_mempool/rte_mempool.h
+++ b/lib/librte_mempool/rte_mempool.h
@@ -385,6 +385,12 @@ typedef int (*rte_mempool_dequeue_t)(struct rte_mempool *mp,
  */
 typedef unsigned (*rte_mempool_get_count)(const struct rte_mempool *mp);
 
+/**
+ * Return if the given external mempool is available for this instance.
+ * it is optional to implement for mempools
+ */
+typedef int (*rte_mempool_pool_verify)(const struct rte_mempool *mp);
+
 /** Structure defining mempool operations structure */
 struct rte_mempool_ops {
 	char name[RTE_MEMPOOL_OPS_NAMESIZE]; /**< Name of mempool ops struct. */
@@ -393,6 +399,8 @@ struct rte_mempool_ops {
 	rte_mempool_enqueue_t enqueue;   /**< Enqueue an object. */
 	rte_mempool_dequeue_t dequeue;   /**< Dequeue an object. */
 	rte_mempool_get_count get_count; /**< Get qty of available objs. */
+	rte_mempool_pool_verify pool_verify;
+	/**< Verify if external mempool is available for usages*/
 } __rte_cache_aligned;
 
 #define RTE_MEMPOOL_MAX_OPS_IDX 16  /**< Max registered ops structs */
@@ -514,6 +522,18 @@ void
 rte_mempool_ops_free(struct rte_mempool *mp);
 
 /**
+ * @internal wrapper to verify the external mempool availability
+ *
+ * @param mp
+ *   Pointer to the memory pool.
+ * @return
+ *   0: Success; external mempool instance is available
+ * - <0: Error; external mempool instance is not available
+ */
+int
+rte_mempool_ops_pool_verify(const struct rte_mempool *mp);
+
+/**
  * Set the ops of a mempool.
  *
  * This can only be done on a mempool that is not populated, i.e. just after
@@ -529,6 +549,7 @@ rte_mempool_ops_free(struct rte_mempool *mp);
  *   - 0: Success; the mempool is now using the requested ops functions.
  *   - -EINVAL - Invalid ops struct name provided.
  *   - -EEXIST - mempool already has an ops struct assigned.
+ *   - -EOPNOTSUPP  - mempool instance not available.
  */
 int
 rte_mempool_set_ops_byname(struct rte_mempool *mp, const char *name,
diff --git a/lib/librte_mempool/rte_mempool_ops.c b/lib/librte_mempool/rte_mempool_ops.c
index 5f24de2..4119882 100644
--- a/lib/librte_mempool/rte_mempool_ops.c
+++ b/lib/librte_mempool/rte_mempool_ops.c
@@ -123,6 +123,18 @@ rte_mempool_ops_get_count(const struct rte_mempool *mp)
 	return ops->get_count(mp);
 }
 
+/* wrapper to check if given external mempool is available for this instance.*/
+int
+rte_mempool_ops_pool_verify(const struct rte_mempool *mp)
+{
+	struct rte_mempool_ops *ops;
+
+	ops = rte_mempool_get_ops(mp->ops_index);
+	if (ops->pool_verify)
+		return ops->pool_verify(mp);
+	return 0;
+}
+
 /* sets mempool ops previously registered by rte_mempool_register_ops. */
 int
 rte_mempool_set_ops_byname(struct rte_mempool *mp, const char *name,
@@ -146,6 +158,12 @@ rte_mempool_set_ops_byname(struct rte_mempool *mp, const char *name,
 	if (ops == NULL)
 		return -EINVAL;
 
+	/*verify if the given mempool is available for this instance */
+	if (ops->pool_verify) {
+		if (ops->pool_verify(mp))
+			return -EOPNOTSUPP;
+	}
+
 	mp->ops_index = i;
 	mp->pool_config = pool_config;
 	return 0;
diff --git a/lib/librte_mempool/rte_mempool_ring.c b/lib/librte_mempool/rte_mempool_ring.c
index b9aa64d..d86d5e0 100644
--- a/lib/librte_mempool/rte_mempool_ring.c
+++ b/lib/librte_mempool/rte_mempool_ring.c
@@ -126,6 +126,7 @@ static const struct rte_mempool_ops ops_mp_mc = {
 	.enqueue = common_ring_mp_enqueue,
 	.dequeue = common_ring_mc_dequeue,
 	.get_count = common_ring_get_count,
+	.pool_verify = NULL,
 };
 
 static const struct rte_mempool_ops ops_sp_sc = {
@@ -135,6 +136,7 @@ static const struct rte_mempool_ops ops_sp_sc = {
 	.enqueue = common_ring_sp_enqueue,
 	.dequeue = common_ring_sc_dequeue,
 	.get_count = common_ring_get_count,
+	.pool_verify = NULL,
 };
 
 static const struct rte_mempool_ops ops_mp_sc = {
@@ -144,6 +146,7 @@ static const struct rte_mempool_ops ops_mp_sc = {
 	.enqueue = common_ring_mp_enqueue,
 	.dequeue = common_ring_sc_dequeue,
 	.get_count = common_ring_get_count,
+	.pool_verify = NULL,
 };
 
 static const struct rte_mempool_ops ops_sp_mc = {
@@ -153,6 +156,7 @@ static const struct rte_mempool_ops ops_sp_mc = {
 	.enqueue = common_ring_sp_enqueue,
 	.dequeue = common_ring_mc_dequeue,
 	.get_count = common_ring_get_count,
+	.pool_verify = NULL,
 };
 
 MEMPOOL_REGISTER_OPS(ops_mp_mc);
diff --git a/lib/librte_mempool/rte_mempool_stack.c b/lib/librte_mempool/rte_mempool_stack.c
index 5fd8af2..0198b70 100644
--- a/lib/librte_mempool/rte_mempool_stack.c
+++ b/lib/librte_mempool/rte_mempool_stack.c
@@ -141,7 +141,8 @@ static struct rte_mempool_ops ops_stack = {
 	.free = stack_free,
 	.enqueue = stack_enqueue,
 	.dequeue = stack_dequeue,
-	.get_count = stack_get_count
+	.get_count = stack_get_count,
+	.pool_verify = NULL,
 };
 
 MEMPOOL_REGISTER_OPS(ops_stack);
-- 
1.9.1