In order to avoid breaking Vhost-user live-migration, we want the
rte_vhost_driver_set_max_queue_num API to only be effective with
VDUSE.
Furthermore, this API is only really needed for VDUSE where the
device number of queues is defined by the backend. For Vhost-user,
this is defined by the frontend (e.g. QEMU), so the advantages of
restricting more the maximum number of queue pairs is limited to
a small memory gain (a handful of pointers).
Fixes: 4aa1f88ac13d ("vhost: add API to set max queue pairs")
Cc: sta...@dpdk.org
Reported-by: Yu Jiang <yux.ji...@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
Changes in v2:
==============
- Document the change in the API (David)
---
lib/vhost/rte_vhost.h | 2 ++
lib/vhost/socket.c | 12 ++++++++++++
2 files changed, 14 insertions(+)
diff --git a/lib/vhost/rte_vhost.h b/lib/vhost/rte_vhost.h
index b0434c4b8d..328281ba0f 100644
--- a/lib/vhost/rte_vhost.h
+++ b/lib/vhost/rte_vhost.h
@@ -614,6 +614,8 @@ rte_vhost_driver_get_queue_num(const char *path, uint32_t
*queue_num);
* @b EXPERIMENTAL: this API may change, or be removed, without prior notice.
*
* Set the maximum number of queue pairs supported by the device.
+ * The value set is ignored for Vhost-user backends. It is only taken into
+ * account with VDUSE backends.
*
* @param path
* The vhost-user socket file path
diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
index a75728a2e4..d29d15494c 100644
--- a/lib/vhost/socket.c
+++ b/lib/vhost/socket.c
@@ -860,6 +860,18 @@ rte_vhost_driver_set_max_queue_num(const char *path,
uint32_t max_queue_pairs)
goto unlock_exit;
}
+ /*
+ * This is only useful for VDUSE for which number of virtqueues is set
+ * by the backend. For Vhost-user, the number of virtqueues is defined
+ * by the frontend.
+ */
+ if (!vsocket->is_vduse) {
+ VHOST_CONFIG_LOG(path, DEBUG,
+ "Keeping %u max queue pairs for Vhost-user
backend",
+ VHOST_MAX_QUEUE_PAIRS);
+ goto unlock_exit;
+ }
+
vsocket->max_queue_pairs = max_queue_pairs;
unlock_exit:
--
2.46.1
